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Above Average Precipitation in 2017 for Contiguous USA

2017 was the 19th wettest year on record across the contiguous USA.

Figure 1. Source: NOAA, Climate-at-a-Glance.

So says data from Climate-At-A-Glance, the data portal operated by the National Oceanographic and Atmospheric Administration (NOAA). Figure 1 shows the data, with the green line representing actual yearly precipitation, and the blue line representing the trend across time. The left vertical scale shows inches of precipitation, while the right shows millimeters of precipitation. In 2017, the average precipitation across the contiguous USA was 32.21 inches, which was the 19th highest amount in the record. Over time, precipitation seems to be increasing at about 0.17 inches per decade. The trend towards more precipitation is present in the Eastern Climate Region (+0.25 inches per decade), the Southern Climate Region (+0.22 inches per decade), and the Central Climate Region (+0.22 inches per decade). It is almost absent in the Western Climate Region, however (+0.03 inches per decade). (Except where noted, data is from the Climate-at-a-Glance data portal.)

(Click on figure for larger view.)

Figure 2. Source: NOAA, Climate-at-a-Glance.

In Missouri, 2017 was the 51st wettest year on record, with 41.22 inches of precipitation. (Figure 2) This puts the year slightly above the long-term average. As expected, the variation from year-to-year is much larger than the change in precipitation over time, but since 1895 Missouri has trended towards about 0.24 inches more precipitation per decade.

The interesting thing about Missouri’s precipitation is that in each of the last 2 years, concentrated storm systems have moved across the state from southwest to northeast, roughly following the route of I-44. They have led to huge amounts of rain over periods of a couple of days, resulting in damaging flooding. (See here and here.) This pattern is the one predicted by climate change models – slightly increased precipitation occurring in heavy precipitation events, with longer, drier spells between. (Drier because increased temperatures will cause the soil to dry out more quickly.)

Table 3. Source: NOAA, Climate-at-a-Glance.

The Northern Rockies and Plains are where most of the water that flows into the Missouri River originates, and the Missouri River provides water to more Missourians than any other source. This region saw 21.17 inches of precipitation in 2017, some 0.28 inches below average. (Figure 3) As expected, the variation between years is much larger than the change over time, but here, too, precipitation has been increasing, though the change has only been +0.07 inches per decade.

What to watch for in Missouri, then, does not appear to be a decrease in average yearly precipitation, but two other issues. First, demand for water has been increasing. Will it grow to outstrip the supply? Second, climate change is causing precipitation that once fell as snow to fall as rain. This changes the timing of when the Missouri River receives the runoff. Will that affect the ability of the river to supply water to meet the demand for water? So far, these answers are not known. (For a more extended discussion, see here.)

Figure 4. Source: NOAA, Climate-at-a-Glance.

The water situation in California is more serious than it is in the Northern Rockies and Plains, Missouri, or contiguous USA. California has a monsoonal precipitation pattern, and it has regions that receive a great deal of precipitation, while other regions receive little, if any. Consequently, the state relies on snowfall during the winter, which runs off during the spring and early summer, and is collected into reservoirs. This water is then distributed around the state. Thus, the amount of water contained in the snowpack on April 1, which is when it historically started melting in earnest, has been seen to be crucial to California’s water status.

After a severe, multi-year drought, last year was a big water year in California. (Figure 4) They received huge amounts of snow during January and February. For instance, the Mammoth Mountain Ski Area received 408 inches of snow during the 2 months. (Mammoth Mountain 2018) Over the whole year California received 27.63 inches of precipitation. That is the 22nd highest amount in the record, and it is 5.24 inches more than average.

Figure 5. Source: California Data Exchange Center, Dept. of Water Resources.

Unfortunately, this winter is not being as kind to California as last year, at least not so far. December, 2017, was the 2nd driest December on record, with only 1989 being dryer. The snowpack measurements suggest that the state has only about 22% of the snowpack that is average for this time of year (Figure 5, data as of 1/22/2018, California Snowpack Survey 2018) This is echoed by data from the Mammoth Mountain Ski Area, which reports only 73 inches of snow to date, vs. 349.5 inches through the end of January last year. (As I write, there are a few days left in January, but it still looks like a very serious shortfall to me.)

The snowpack is also below average in the Colorado River Basin above Lake Powell, the other major source for California’s water. As of 1/28/2018, the snowpack is only 65% of the average for this date. (National Resource Conservation Service, 1/28/2018) Now, snow tends to fall during storms, and there is no predicting when the storms will come. February and March could still bring much-needed snow. But California just got out of a terrible multi-year drought, and it would be very disappointing if it went right back into another after only 1 year.

ADDENDUM: A few days after I wrote this article, the New York Times published one on the water crisis in Cape Town, South Africa. That city is only about 3 months from running completely out of water. This blog focuses on statistics and big pictures. If you want a perspective on what such a crisis might actually look like in an urban area, I recommend the Times article.


California Data Exchange Center, Department of Water Resources. Current Year Regional Snow Sensor Water Content Chart (PDF). Downloaded 1/22/2018 from https://cdec.water.ca.gov/water_cond.html.

Mammoth Mountain Ski Area. 2018. Snow Conditions and Weather: Snow History. Viewed online 1/15/2018 at NOAA National Centers for Environmental information, Climate at a Glance: U.S. Time Series, published January 2018, retrieved on January 15, 2018 from http://www.ncdc.noaa.gov/cag.

Natural Resource Conservation Service, U.S. Department of Agriculture. Upper Colorado River Basin SNOTEL Snowpack Update Report. Viewed online 1/28/2018 at https://wcc.sc.egov.usda.gov/reports/UpdateReport.html?textReport.

NOAA National Centers for Environmental information, Climate at a Glance: U.S. Time Series, published January 2018, retrieved on January 15, 2018 from http://www.ncdc.noaa.gov/cag.

The Second Warmest Year Ever

2017 was the 2nd warmest year on record globally, and the 3rd warmest for the contiguous USA.

Figure 1. Data source: NOAA, Climate-at-a-Glance.

Figure 1 shows the average annual temperature for the Earth from 1880-2017. The chart shows the temperature as an anomaly. That means that they calculated the mean annual temperature for the whole series, and then presented the data as a deviation from that mean. Degrees Celsius are on the left vertical axis, and degrees Fahrenheit are on the right. Because the earth contains very hot regions near the equator and very cold polar regions, the actual mean temperature has relatively little meaning, and Climate-at-a Glance does not include it in their chart. (Except where noted, all data is from NOAA, Climate at a Glance.) 2016 was the highest on record, but 2017 was second. The 4 highest readings have all occurred within the last 4 years. You can see that the Earth appears to have been in a cooling trend until around 1910, then a warming trend until mid-Century, then a cooling period until the late 1960s or early 1970s, and then a warming period since 1970. Over the whole series, the warming trend has been 0.07°C per decade, which equals 0.13°F per decade. Since 1970, however, the warming has accelerated to 0.18°C per decade (0.32°F).

(Click on chart for larger view.)

Figure 2. Data source: NOAA, Climate-at-a-Glance.

Figure 2 shows the average yearly temperature for the contiguous United States from 1895 to 2017. In this chart and those that follow, the vertical axes are reversed, with °F on the left vertical axis, and °C on the right. The purple line shows the data, and the blue line shows the trend. 2017 was the 3rd highest in the record at 54.58°F. The 4 highest readings have all come within the last 6 years. Over time, the average temperature has increased 0.15°F per decade. Since 1970, however, the rate has increased to 0.52°F per decade.


Figure 3. Data source: NOAA, Climate-at-a-Glance.

Figure 3 shows the average temperature across Missouri for 2017. Across the state, it was the 8th warmest year on record, with an average temperature of 57.1°F. In Missouri, the warming trend from 1930-1950 was more moderate than it was nationally, and the trend has been for a 0.1°F increase in temperature each decade. Since 1970, however, the increase has accelerated to 0.4°F per decade.




Figure 4. Data source: NOAA, Climate-at-a-Glance.

Because conditions in the Northern Rockies and Plains affect how much water flows into the Missouri River, which provides more of Missouri’s water supply than any other source, I have also tracked climate statistics for that region. Figure 4 shows the data. Last year was the 11th warmest in the record at 44.9°F. This region has been warming at a rate of 0.2°F per decade over the whole period, but since 1970, the rate has accelerated to 0.5°F per decade.




Figure 5. Data source: NOAA, Climate-at-a-Glance.

Because I have been concerned about the water supply in California, I also track the climate statistics for that state. Figure 5 shows the data. Last year was the third warmest year in the record, with an average temperature of 60.3°F. California has been warming at a rate of 0.2°F each decade. Since 1970 the rate of increase has accelerated to 0.5°F per decade.

In all 4 locations the average yearly temperature seems to have increased significantly for several decades, then paused during mid-Century, and then resumed climbing, but at an accelerated rate. There seems to be little doubt that across the country it is warmer than it was. In Missouri, the average yearly temperature has been increasing, but at a rate that is somewhat less than in the other locations I looked at.


NOAA National Centers for Environmental information, Climate at a Glance: U.S. Time Series, published January 2018, retrieved on January 15, 2018 from http://www.ncdc.noaa.gov/cag.

Did Missouri Have Record Cold?

We’ve had some cold weather in Missouri recently. St. Louis hit -6°F on New Years Day, while Kansas City hit -11°F. But these are not records. The record low on New Years day is -10°F in St. Louis, and -13°F in Kansas City.

Kansas City’s all-time record low is -23°F, which occurred in December 1989.

Figure 1. Data source: National Weather Service, St. Louis Forecast Offices, Personal communication from Spencer Mell.

Figure 1 shows a chart for each winter (December, January, and February). Blue columns are the number of days with a low temperature at or below 0°F in St. Louis, and they run from 1874 to 2016. Red columns are for Kansas City, and they run from 1888 to 2016. The dashed blue line represents the trend over time for St. Louis, the dashed red line for Kansas City. You can see that the number of days varies widely from year-to-year. Many years have 1 day, or even none. In St. Louis the maximum number of days was 18, and it occurred in the winter that began in December 1935. In Kansas City, the maximum number of days was 19, and it occurred twice: in 1935 and 1978.

The trend lines show that in Kansas City, the number of days has not been changing over time. In St. Louis, however, the number of days has decreased over time.

(Click on figure for larger view.)

Figure 2. Data source: National Weather Service, St. Louis Forecast Offices, Personal communication from Spencer Mell.

One can count the number of winters that had 0 days below 0°F, the number of winters that had 1 day, the number of winters that had 2 days, etc. You can then construct a frequency chart of how many years had each number of days. Figure 2 shows such a frequency chart for St. Louis and Kansas City. There have been 54 winters in St. Louis when there were no days with lows at or below 0°F, there have been 28 such winters in Kansas City, and no other number is represented in more years than that.

The number of extremely cold days varies widely from year-to-year, but in St. Louis the average number is 3, and in Kansas City it is 4. St. Louis has experienced 2 days below 0°F this winter, and Kansas City has experienced 4 (both as of 1/16). For comparison, St. Louis has had more than 2 days below 0°F some 51 times since 1874. Kansas City has had more than 4 days below 0°F some 31 times since 1888.

The severe cold began this year on the morning of New Years Day. What about last year? Was it a hot one, or not so hot? The next post will review average temperatures for all of 2017.


National Weather Service, Kansas City Forecast Office. 2018. WFO Monthly/Daily Climate Data. Data viewed online 1/15/2018 at http://w2.weather.gov/climate/getclimate.php?date=&wfo=eax&sid=MCI&pil=CF6&recent=yes&specdate=2017-12-31+11%3A11%3A11.

National Weather Service, St. Louis Forecast Office. 2018. Ranked Occurrences of Temperature <= 32 and 0 Degrees (1893-Present). Downloaded 1/15/2018 from http://www.weather.gove/lsx/cli_archive. (Actually contains data back to 1874).

Personal communication from Spencer Mell, Climate Focal Point, National Weather Service, Kansas City Forecast Office.

Record Damage from Disasters in 2017

2017 was a record year for disasters, and in contrast to recent years, the disasters were focused on the United States.

Worldwide losses from disasters summed to$330 billion in 2017, of which only $135 billion was insured, according to a report from Munich Re, an international reinsurance company. Only one other year has seen greater losses: 2011, when the Tohoku earthquake in Japan led to the devastating tsunami and the nuclear meltdown at the Fukushima Daiichi Reactor. The 2017 total was almost double the average loss over the previous 10 years, even adjusting for inflation ($170 billion). (Except as noted below, data from Munich Re 2017. This is a press release from an insurance company. I generally regard peer-reviewed scientific studies, and government report to be more reliable sources. However, it will be some time before those sources report on this data. So think of these numbers as preliminary data that may undergo some revision.)

The total number of disasters numbered 710, an increase from the 10-year average of 605. In 2017, approximately 10,000 people lost their lives to disasters, which is considerably lower than the 10-year average of 60,000.

The United States accounted for 50% of the losses, compared to the long-term average of 32%, and taking a wider view, North America accounted for 83% of them. The major disasters striking the USA and North America were weather related in 2017 (in contrast to the Tohoku earthquake, which was not). Think back through the year, and quite a list comes to mind:

  • Hurricane Harvey made landfall in Texas on August 26, and devastated the region. With losses summing to approximately $85 billion, it was the costliest disaster of 2017.
  • On September 5, Hurricane Irma, the strongest hurricane ever in the open Atlantic, began blowing a swath of destruction through the Caribbean before crossing the Florida Keys, then traveling south-to-north up the Florida Peninsula. Insured losses were $32 billion, uninsured losses are not yet known.
  • Hurricane Maria, the second Category 5 hurricane to clobber the Caribbean in 2 weeks, slammed into Dominica on September 18, before totally devastating Puerto Rico. Total losses have not yet been calculated, but as of this writing, almost 3 months later, more than 1/4 of the island of Puerto Rico remains without electricity. (StatusPR 1/8/2018)
  • Terrible wildfires swept across North America in 2017. The National Interagency Fire Center has not yet posted summary statistics for the year. However, InciWeb indicates that the largest were two fires in Oklahoma: the Northwest Oklahoma Complex, at 779,292 acres, and the Starbuck Fire, at 623,000 acres. Eleven other fires consumed over 100,000 acres. Of course, the ones that grabbed the headlines were in California. In October, 250 wildfires ignited across Northern California, burning over 245,000 acres and causing more than $9.4 billion in damage; 44 people were killed and 8,900 structures were destroyed. In December, a new round of fires broke out north of Los Angeles and East of Santa Barbara. More than 230,000 people were forced to evacuate, over 1,300 structures were destroyed, and 307,900 acres were consumed. (Inciweb, Wikipedia, 2018).
  • During the Spring, a series of severe thunderstorms with accompanying tornadoes and hail, caused insured losses of over $1 billion. These included record floods across Southern Missouri, as 8-12 inches of rain fell over 48 hours in some areas. (National Weather Service 2017)
  • In Asia, some 2,700 people lost their lives due to flooding resulting from an extremely severe monsoon season. In some districts, 3/4 of the territory was under water.

The fires that struck California were unprecedented, and yet, the acres burned by the fires in Oklahoma were more than 5 times larger. The devastation wrought by the hurricanes was beyond imagination – whole islands were virtually destroyed.

As reported many times in this blog, weather conditions play a role in hurricanes, wildfires, and flooding. While my reviews have indicated that damage from weather-related disasters is highly variable from year-to-year, there has also been a clear trend toward more damage. While humans play a role by living in harms way, climate change does, too.

The report from Munich Re includes the following statement: “A key point is that some of the catastrophic events…are giving us a foretaste of what is to come. Because even though individual events cannot be directly traced to climate change, our experts expect such extreme weather to occur more often in the future.” (p.2)

More detailed information on disasters and severe weather events in Missouri and the USA will become available later in the year. The next post will look at 2017 summary weather patterns in Missouri and across the USA.


InciWeb, Incident Information System. This is the portal for an interagency information management system. Data was viewed online 1/8/2018 at https://inciweb.nwcg.gov.

Munich Re. 2018. Natural Catastrophe Review: Series of Hurricanes Makes 2017 Year of Highest Insured Losses Ever. Press release downloaded 1/5/2018 from https://www.munichre.com/en/media-relations/publications/press-releases/2018/2018-01-04-press-release/index.html.

National Weather Service. 2017. Historic Flooding Event — 28-30 April 2017. Viewed online 1/8/2018 at https://www.weather.gov/sgf/28-30AprilHistoricFloodingEvent.

StatusPR. Website viewed online 1/8/2018 at http://status.pr.

Wikipedia. 2018. 2017 California Fires. Downloaded 1/8/2018 from https://en.wikipedia.org/wiki/2017_California_wildfires.

California Ablaze: Nature’s Revenge?

Fires torch hundreds of thousands of acres in California.

Just a few short weeks ago I discussed the terrible hurricanes that affected Houston, the Caribbean Islands, and Florida this year. Now, the headlines are full of the wildfires that have been raging in California.

By late September, it had already been a heavy forest fire season in the western United States. Then, over the weekend of October 7-8, wildfires broke out in the area around the Napa and Sonoma Valleys. Fanned by hot, dry winds, they spread unbelievably quickly, burning 155,509 of acres (as of 10/17/2017), including prime wine producing vineyards, and thousands of homes (CALFIRE 2017b). Dozens were killed. Figure 1 shows the Coffee Park area of Santa Rosa in 2015. Figure 2 shows it after the fire. The gray areas are homes that have been burned – I mean burned to the ground, reduced to ashes. (City of Santa Rosa 2017)

Figure 1: Coffee Park Neighborhood, Santa Rosa CA, in 2015. Source: City of Santa Rosa.

Figure 2. Coffee Park Neighborhood, Santa Rosa CA, after the fire. Source: City of Santa Rosa.












All totaled, as of 10/15/2017 CALFIRE lists 7,980 fires in California that have burned 1,046,995 acres (1,636 sq. mi.) (CALFIRE 2017b). Figure 3 shows a map of the fires. Maps such as this one tend not to be comprehensive, as they map the fires to which the specific agency has responded. (CALFIRE 2017a) Across the United States, as of 10/17/2017 there have been 51,435 wildfires that have burned 8,769,877 acres. That puts 2017 among the top 10 fire years ever, and compares to an average of 6,016,599 acres from 2006-2016. Figure 4 shows the data. Data collection methods changed after 1984, which is why I have used different colors for before and after that year. (National Interagency Fire Center)

Figure 3. Fires Responded to by CALFIRE in 2017. Source: CALFIRE, 2017.

Figure 4. Data source: National Interagency Fire Center, 2017.













At a recent workshop of wildland fire experts, the consensus was that the United States was experiencing wildland fires that were behaving in aggressive, destructive ways that had never been experienced before. (National Academy of Sciences, Engineering, and Medicine 2017) What is going on?

In a series of posts last year, I explored the role that wildfire plays in western forests and showed that, though the number of fires did not seem to be trending higher, the number of acres burned per fire did. The result was that more acres per year were burning. There seemed to be 3 causes. One was that, while for decades fire was regarded as an unmitigated evil and suppressed as vigorously as possible, it was now regarded as a necessary part of forest ecology, and was allowed to burn without suppression efforts in some cases. A second reason was that decades of suppression had left western forests littered with dead and downed wood, perfect conditions for small fires to grow into huge raging crown fires that destroyed tens of thousands of acres. And a third reason was that climate change had raised summer temperatures, causing forests to dry out earlier in the season, turning small fires that would extinguish on their own into large, destructive fires.

Early fall is the driest time of year in the regions around the Napa and Sonoma Valleys. Typically, it has rained very little or not at all since March or April; the grasslands are brown and sere, the forests dry and brittle. Then, in October, the wind starts to blow: the Diablo Winds in Northern California, and the Santa Ana Winds in Southern California. Fueled by high pressure over the central United States and lower pressure over the coast, the winds rush over the Sierra Madre Mountains, down the passes and valleys, and through the lowlands. It happens every year. This year, when the fires started near the Napa and Sonoma Valleys, gusts were blowing at 79 m.p.h. Recent research suggests that the winds may be getting hotter and drier as a result of climate change. (Fountain, 2017)

Wildfire needs three things to grow, and it got all of them: warm temperatures, lots of dry fuel, and high winds that were hot and dry. The fires blew up into raging infernos. Blowing sparks along at 70+ m.p.h., the wind and the fire outraced the firefighters. In a span of only a few hours, tens of thousands of acres were reduced to ashes, whole neighborhoods were destroyed, and dozens were killed.

Hurricanes in the Atlantic, fires across the West, deluges and record heat in Australia, terrible floods in Asia, drought and desertification in some parts of Africa and floods in other parts: is Mother Nature mad at us? Is she exacting revenge for the way we have mistreated Her all these years? To borrow a thought from Abraham Lincoln: if we shall suppose that environmental destruction is an offense against Nature, and that humankind has caused that offense, and that suffering inevitably comes to those who commit such offenses, and if Nature now gives to us these terrible disasters as due to those who have caused the offenses, then shall we see in them anything but a judgment and a justice that is altogether true and righteous? “Woe unto the world because of offenses.” (Lincoln, 1865)


CALFIRE. 2017a. Incident Information: Number of Fires and Acres. Viewed online 10/17/2017 at http://cdfdata.fire.ca.gov/incidents/incidents_stats?year=2017.

Cal Fire. 2017b. Statewide Fire Maps. Downloaded 2017-10-17 from http://www.fire.ca.gov/current_incidents.

City of Santa Rosa. 2017. Emergency Information Homepage: Fire Aerial Photo Comparison. Downloaded 2017-10-17 from https://www.srcity.org/2620/Emergency-Information.

Fountain, Henry. 2017. “California Winds are Fueling Fires. It May Be Getting Worse. New York Times, 10/11/2017. Viewed online 10/17/2017 at https://www.nytimes.com/2017/10/11/climate/caifornia-fires-wind.html?action=click&contentCollection=climate&region=rank&module=package&version=highlights&contentPlacement=1&pgtype=sectionfront.

Lincoln, Abraham. 1865. Second Inaugural Address. Viewed online 10/17/2017 at http://www.bartleby.com/124/pres32.html.

National Academies of Sciences, Engineering, and Medicine. 2017. A Century of Wildland Fire Research: Contributions to Long-term Approaches for Wildland Fire Manage- ment: Proceedings of a Workshop. Washington, DC: The National Academies Press. doi: https://doi. org/10.17226/24792. Downloaded 8/25/2017 from http://nap.edu/24792.
National Interagency Fire Center. Year-to-Date Statistics. Viewed online 10/17/2017 at https://www.nifc.gov/fireInfo/nfn.htm.

Damaging Weather Events in Missouri

Figure 1. Data source: Office of Climate, Water, and Weather Services.

Damage from sever weather in Missouri shows a different pattern than does damage nationwide. As Figure 1 shows, the cost of damage from hazardous weather events in Missouri spiked in 2007, then really spiked in 2011. Since then, it has returned to a comparatively low level. The bulk of the damage in 2011 was from 2 tornado outbreaks. One hit the St. Louis area, damaging Lamber Field. The second devastated Joplin, killing 158, injuring 1,150, and causing damage estimated at $2.8 billion. The damages in 2007 came primarily from two winter storms, one early in the year, one late. In both cases, hundreds of thousands were without power, and traffic accidents spiked.

In 2015 Missouri saw an increase in weather-related damage, primarily due to the flooding that struck between Christmas and New Years that year. There was similar flooding this year in April, so 2017 will likely see a similar increase.

Figure 2. Data source: Office of Climate, Water, and Weather Services.

Figure 2 shows deaths and injuries in Missouri from hazardous weather. Deaths are in blue and should be read on the left vertical axis. Injuries are in red and should be read on the right vertical axis. The large number of injuries and deaths in 2011 were primarily from the Joplin tornado. In 2006 and 2007, injuries spiked, but fatalities did not. The injuries mostly represented non-fatal auto accidents from winter ice storms. The fatalities in 1999 resulted from a tornado outbreak.

The Missouri data covers fewer years than the national data discussed in my previous post. It also covers all hazardous weather, in contrast to the national data, which covered billion dollar weather disasters.

While the national data shows a clear trend towards more big weather disasters, Missouri’s data does not. The Missouri data seems to reflect the kind of disaster that occurred and where it occurred. Tornadoes, if they hit developed areas, cause injuries, deaths, and lots of damage. Floods cause fewer injuries and deaths; damage can be significant, but it is limited to the floodplain of the river that flooded. Ice storms affect widespread areas; damages come mostly through loss of the electrical grid and car crashes, which cause many injuries, but fewer deaths.


Office of Climate, Water, and Weather Services, National Weather Service. 2016. Natural Hazard Statistics. Data downloaded 9/11/2017 from http://www.nws.noaa.gov/om/hazstats.shtml#.

InflationData.com. 2016. Historical Consumer Price Index (CPI-U) Data. Data downloaded 2/10/16 from http://inflationdata.com/Inflation/Consumer_Price_Index/HistoricalCPI.aspx?reloaded=true.

Missouri State Emergency Management Agency. Declared Disasters in Missouri. Viewed online 9/12/2017 at https://sema.dps.mo.gov/maps_and_disasters/disasters.

Descriptions of specific weather events, if they are large and significant, can be found on the websites of the Federal Emergency Management Administration, the Missouri State Emergency Management Agency, and local weather forecast offices. However, in my experience, the best descriptions are often on Wikipedia.

Severe Storms on the Increase

The number of severe storms is increasing, and so is their intensity.

Figure 1. Source: NOAA National Centers for Environmental Information.

In the previous post I noted that Hurricane Harvey was one in a series of storms that have devastated Houston, and indeed, the country as a whole. I asked what is going on, and whether it has always been this way.

The National Centers for Environmental Information tracks weather disasters that cause over $1 billion in damages. Figure 1 shows how many there have been each year going back to 1980. The number varies from year-to-year, but over time there has been a significant increase – there weren’t any in 1987, but in 2011 there were 16. Through July 7, 2017, roughly half the year, there have been 9.

(Click on chart for larger view.)

In the chart, the colors represent different types of weather disasters. Storms are divided into 3 categories: winter storms, which involve ice and snow, tropical cyclones (like Hurricane Harvey or Tropical Storm Irene), and severe storms. This last category includes thunderstorms and tornadoes, as well as severe rain events like the ones that caused flooding in Missouri in December 2015 and April 2017. You can see that the increased number of billion-dollar disasters has come from an increase in the number of severe storms. It has not come from tropical storms or winter storms.

Figure 2. Data source: NOAA National Centers for Environmental Information.

Figure 2 shows the damage cost from billion-dollar weather disasters each year. The damage cost is adjusted for inflation. The chart shows that there are many years when the total cost is below $25 billion. However, there are also years where the amount of damage spikes. The year with the largest damage was 2005, when Hurricane Katrina devastated New Orleans and a wide swath of the Gulf Coast, and damage topped $213 billion. That’s quite a chunk of change. The second highest cost occurred in 2012, when Hurricane Sandy came ashore in New York. This year, 2017, only includes damage up to July 7, so it doesn’t include Hurricane Harvey or Irma. I have seen news stories that the cost of damage from Hurricane Harvey may reach $150 billion, and Irma will add billions more. By the time the year is done, the damage cost is likely to be the highest in history.


Figure 3. Data source: NOAA, National Centers for Environmental Information.

Figure 3 shows the number of billion dollar weather disasters by type (through 7/7/2017). Since 1980, there have been a total of 212. Severe storms have accounted for 42% of the events.








Figure 4. Data source: NOAA National Centers for Environmental Information.

Figure 4 shows the total costs of billion dollar weather disasters by type (through 7/7/2017). Since 1980 costs have totaled $1.24 trillion dollars, and tropical cyclones have accounted for about 47% of the total cost. Though they constitute the largest number of events, severe storms account for only 16% of the cost of damages. That is because such storms, while severe, affect relatively small areas. Tropical storms and droughts, on the other hand, affect much larger areas.





Figure 5. Miami Beach in 1925. Source: Miami Design Preservation League.

All of the highest cost years have occurred since 2004. The data is inflation-adjusted, so that should not be the reason. One possible reason not related to the weather is that there are more people living in harms way – the population living along the coast has grown, and sprawl has caused more of the landscape to be covered with development, increasing the likelihood that a severe storm will hit something and damage it. For instance, in 1920 the population of Miami-Dade County (the location of the City of Miami) was 42,753 (that’s right, less than 50,000). But in 2010 it was 2,507,362. In 1992, when Hurricane Andrew devastated Homestead, a small community southwest of Miami, the area between Miami and Homestead was mostly open agricultural fields. Today, just 15 years later, it has filled-in, and is one continuous urban area. This story has been repeated all along the coasts of America, and in many inland areas as well. (See here.)





Figure 6. Intensity of Tropical Storms. Source: Kossin et al, 2013.

But I think that’s only part of the story. The number of tropical storms striking the U.S. may not have increased, but their intensity has. Figure 6 shows the intensity of tropical storms in different regions of the world over time. LMI stands for the lifetime maximum intensity of the wind in a storm, in meters per second. The lines represent quantiles. The 0.9 line (pinkish-purple) means that 90% of all storms that year were less intense than that value. The 0.8 line (light blue) means that 80% of all storms were less intense than that value, and so on. The authors dropped trend lines on the chart for each quantile. In the North Atlantic, storms have increased in intensity a lot. Those are the storms that strike the East Coast and Gulf Coast of the United States.


Figure 7. Source: GlobalChange.gov.

Other kinds of heavy precipitation events are also on the rise, as I reported here. Figure 7 repeats a chart from that post showing the trend over time.

Scientists project that climate change will cause an increase in storm intensity and in heavy rain events. It seems that this is not a prediction for the future, it is already happening. One cannot say that any individual storm is caused by climate change, but storms like Hurricane Harvey, Tropical Storm Irene, and the April storm in Missouri are already “more common,” and are likely to be even more “more common” in the future.


GlobalChange.gov. Broadcase_Trends-in-heavy-precip_V2. National Climate Assessment 2014. Downloads, Graphics (Broadcast). Downloaded 11/13/2016 from http://nca2014.globalchange.gov/downloads.

Kossin, James, Timothy Olander, and Kenneth Knapp. 2013. Trend Analysis with a New Global Record of Tropical Cyclone Intensity. Journal of Climate, 26, 9960-9976.

Miami Design Preservation League. Collins Ave. at 63rd Street in 1925.Downloaded 9/8/2017 from https://www.pinterest.com/pin/189714203027788727.

NOAA National Centers for Environmental Information (NCEI). U.S. Billion-Dollar Weather and Climate Disasters (2017). https://www.ncdc.noaa.gov/billions.

Wikipedia. Miami-Dade County, Florida. Viewed online 9/8/2017 at https://en.wikipedia.org/wiki/Miami-Dade_County,_Florida#2010_U.S._Census.

Hurricane Harvey Devastates Houston

Hurricane Harvey caused record flooding in Houston. Those poor people!

Figure 1. Flooding in Port Arthur, TX, from Hurricane Harvey. Source: South Carolina National Guard, 2017.

Most of you know about the terrible disaster that Hurrican Harvey caused in Houston, TX. The disaster will inevitably be compared to Hurricane Katrina and the flood that struck New Orleans. In both cases, a major city was flooded by a hurricane. Houston, however, is a metropolitan area with a population of about 6.3 million people, while New Orleans is a metropolitan area with a population of about 1.3 million. That means that Houston is almost 5 times as large.

New Orleans flooded so catastrophically because much of the city is below sea level. The levies broke, the ocean poured through, and the low areas filled up with water just like a bathtub would. Coastal Texas is a flat, low-lying area, some of which was swamp or marshland before being developed. It is not below sea level, however. Houston flooded because Hurricane Harvey dumped prodigious amounts of rain on the city – more than 4 feet of rain in some areas. The water couldn’t run off fast enough, and flooding occurred. The tragedy has been well covered by all of the national news sources, so I have contented myself with a single photograph of the flooding in Port Arthur, a small city about 100 miles northeast of Houston. (Figure 1) This blog focuses not on individual events, but on trends and on the big picture.

(Click on photo for larger view.)

Figure 2. Flooding in Houston from Tropical Storm Allison in 2001. Source: Harris County Flood Control District.

Houston has been hit repeatedly by tropical storms and hurricanes. From 1836 to 1936, the city suffered through 16 major floods, with the water level reaching as high as 40 feet in one of them. Since 1935, there have been 8 more. In 2001, Tropical Storm Allison dumped up to 35 inches of rain on Houston over 5 days, resulting in flooding that damaged over 73,000 homes and caused $5 billion in property damage (see Figure 2). In 2008, Hurricane Ike passed directly over the city, breaking out windows in downtown skyscrapers and wiping out electricity to some customers for over a month. Over the Memorial Day Holiday in 2015, rain of up to 11 inches over 24 hours drenched Houston, flooding thousands of homes. In April 2016 (last year), a trough of rain parked over the city, and over 24 hours, 17 inches of rain fell. They had to rescue 1,800 people from the floods, but even so 8 died and 1,144 homes were inundated.

But flooding is not limited to Houston. In April of this year, flooding in Missouri and Arkansas caused $1.7 billion in damages. In February, flooding in California caused $1.5 billion in damages, including Oroville Dam (see here). In October, 2016, Hurricane Matthew churned along the Atlantic Coast causing damage. In August, 2016, Louisiana received 20-30 inches of rain from a stationary storm, causing $10.3 billion in damages. And a December 2015 storm brought record flooding to Missouri and tornadoes to Texas, causing 50 deaths and $2.5 billion in damages. The list goes on and on.

Figure 3. Hurricane Irma Devastated the Island of St. Maarten. Photo: Gerb van Es, Dutch Department of Defense.

UPDATE: As of 9/8/2017, three more tropical storms have formed in the Atlantic Ocean: Hurricane Irma, a Catagory 5 hurricane (the largest category), passed over several Caribbean islands causing terrible damage (see Figure 3). As I write, it is bearing down on Florida. How bad will it be? We don’t know; it has diminished to a Category 4 hurricane, but it is wider than the Florida Peninsula is, and it is currently forecast to travel south to north right up the entire peninsula. Tropical Storm Jose is gaining strength in the mid-Atlantic, threatening many of the same islands that were just devastated by Irma, though it is forecast to turn north. And Hurricane Katia has formed just north of the Yucatan Peninsula, and is expected to come ashore north of Veracruz, Mexico.

What is happening? Has it always been this way, or is there more very damaging weather than there used to be? The next post will look at the national trend, and the post after that will look at the trend in Missouri.


Gerb van Es, Dutch Department of Defense. Aerial Photo Shows the Damage of hurrican Irma in Phillipsburg, on the Dutch portion of the Caribbean Island of Sint Maarten. Downloaded 9/8/2017 from https://www.caymancompass.com/2017/09/07/enormous-catastrophe-st-martin-reeling-from-hurricane-damage.

Harris County Flood Control District. Harris County’s Flooding History. Viewed online 8/30/2017 at https://www.hcfcd.org/flooding-floodplains/harris-countys-flooding-history.

Harris County Flood Control District. Tropical Storm Allison. Viewed online 8/30/2017 at https://www.hcfcd.org/storm-center/tropical-storm-allison-2001.

NOAA National Centers for Environmental Information (NCEI) U.S. Billion-Dollar Weather and Climate Disasters (2017). https://www.ncdc.noaa.gov/billions.

South Carolina National Guard. 8/31/2017. Image #170831-Z-AH923-081. Downloaded 9/8/2017 from https://commons.wikimedia.org/w/index.php?curid=62096178.

Wikipedia. April 2016 United States Storm Complex. Viewed online 8/30/2017 at https://www.hcfcd.org/storm-center/tropical-storm-allison-2001.

Wikipedia. Houston. Viewed online 8/30/2017 at https://en.wikipedia.org/wiki/Houston.

Wikipedia. New Orleans. Viewed online 8/30/2017 at https://en.wikipedia.org/wiki/Houston.

California Continues to Face Future Water Supply Challenges

Despite the wet winter in 2017, climate change will pose severe challenges to California’s future water supply.

In the last post I reported that Gov. Brown has declared California’s drought emergency officially over. The state has plenty of water for the next year. This post explores the implications of this wet winter for California’s long-term water status.

I first looked at this topic in a 13-post series that ran during the summer of 2015. The series starts here. It contains a lot of information about California’s water supply and consumption. I concluded that at some point in the not-too-distant future California would experience a significant permanent water deficit. The #1 cause of the deficit would be climate change, which is projected to result in a significant reduction in the size of California’s snowcap. The #2 cause would be population increase. I performed the analysis myself because I could find no sources that did anything similar. I’m not going to repeat that analysis in this post. Rather, I’m going to report a couple of new reports that confirm the concerns I had in 2015.

Figure 1. Source: California Dept. of Water Resources.

Figure 1 illustrates the problem California faces. Almost all of California’s precipitation falls during the winter. Some of it gets temporarily “locked up” as snowpack on the Sierra Nevada mountains. Demand for water, however, peaks during the summer. California has many man-made reservoirs that release water during the summer and fall, and the state depends on the melting snowpack to recharge the man-made reservoirs as water is drawn from them. In Figure 1, the blue line represents runoff and the red line represents water demand. You can see that moving the date of maximum runoff earlier in the year increases the amount of water that cannot be captured into storage (yellow area). It has to be dumped; see the post on Oroville Dam to see what happens if the volume of water being dumped gets too high. It increases the amount of water that must be released from storage in the summer and fall. The amount released is now larger than the amount of inflow the reservoir receives, resulting in an increased water deficit (the blue area represents water received, the green area represents water discharged equal to the size of the blue area, and the red area represents the deficit). There is a water deficit in average years, but it is small, and a winter with slightly above average precipitation can make up the deficit. Moving maximum runoff earlier in the year increases the size of the deficit; now only a much wetter year can recharge the reservoirs.

Figure 2. Source: California Dept. of Water Resources.

Figure 2 includes two charts. The first chart shows the percentage of precipitation in California that occurred as rain from 1948-2012. If precipitation occurs as rain, it is not snow and can’t add to the snowpack. On the chart, the black horizontal line is the mean percentage across all years. Red columns represent years with above average percentage of rain, the blue columns below average. There is variation between years, but you can see that the red columns cluster to the right while blue columns cluster to the left. That means that on average an increasing percentage of precipitation is falling as rain. Thus, on average, unless annual precipitation undergoes a sustained increase (which hasn’t happened and is not projected), California’s snowpack will shrink, because what once was snow is now rain.

The second chart in Figure 2 shows runoff measured on the Sacramento River. The red line represents the 50-year period from 1906-1955, while the blue line represents the 52-year period from 1956-2007. This is the specific problem that was discussed conceptually in Figure 1. You can see that runoff has moved earlier in the year by about a month.


Figure 3. Source: National Centers for Environmental Information.

Why is more precipitation falling as rain rather than snow, and why is melt occurring earlier? Because of increased temperature. Winter is when the snow falls in California, and it is when the state receives the bulk of its precipitation. Figure 3 shows that the average winter temperature (December – March) has increased more than 2°F. In addition, if you look at Figure 3 carefully, you can see that the rate of temperature increase accelerated somewhere around 1980. The runoff chart in Figure 2 chunks the data into only 2 groups, each about 50 years long. Because of the acceleration in the increase in temperature, I believe that if they had chunked the data into 3 groups, each about 33 years long, the change towards earlier snowmelt would have been even greater than the one shown.

How dire is the threat is to California’s snowpack? It depends on which climate projection is used. The projected effects of climate change depend very much on how humankind responds to the threat. If we greatly reduce our GHG emissions immediately, the climate will warm less; if we don’t, it will warm more.

Figure 4. Source: California Dept. of Water Resources.

Figure 4 shows the historical size of the California snowpack plus 2 projections. The middle map show the projected size of the snow pack if warming is less. The map on the right shows its size if warming is more. You can see that, even under the low warming scenario, a loss of 48% of the snowpack is projected. Under the high warming scenario, a 65% loss of the snowpack is projected. These projections are for the end of the century. In my original series, I estimated the loss of snowpack at 40% by mid-century. That is not too far off from the high warming scenario. And I have to say, the evidence suggests that so far the world is operating under the high warming scenario, possibly, even worse.

Surface water is not the only source on which California depends. California withdraws significant amounts of water from underground aquifers, especially in (but not limited to) the agricultural areas of the Central Valley. Aquifers can be compared to underground lakes, but don’t think of them as being like a big, hollow cave in which there is a concentrated, pure body of water. Rather, think of them as regions of porous ground, such as gravel or sand. In between the pieces of gravel or sand is space, and that space can hold water. Below and on the sides are rocks or clay that are impervious to water, which allow the water to be held in the aquifer.

So long as the aquifer is charged with water, this is a situation that can last for thousands of years. If, however, water is pumped out without being replaced, then nothing occupies the spaces between the pieces of gravel or sand. If that occurs, the weight of the ground over the aquifer can compress the aquifer, reducing the amount of space available between the pieces of sand and gravel, reducing the capacity of the aquifer to hold water. When this occurs, it sometimes shows up as subsidence on the surface. In California, it is primarily the snowpack that feeds the aquifers. If a significant amount of the snowpack is lost, it will be less able to recharge the aquifers, and they will undergo increased compaction.

Figure 5. Map of Permanent Subsidence. Source: Smith et al, 2016.

As noted in my original series, significant subsidence has already occurred over California’s aquifers. More seems to be occurring every year. A recent study attempted to quantify the amount of water storage capacity being lost to compaction. The study covered the years 2007-2010, so it didn’t even include the recent severe drought (2007, 2008, and 2009 were dry years, but 2010 was 9th wettest in the record). The study covered only a small portion of the south end of the Central Valley Aquifer, yet it found that during those 4 years significant permanent subsidence had occurred (see Figure 5), resulting in a total loss of 748 million cubic meters of water storage, an amount roughly equal to 9% of the groundwater pumping that occurs in the study area. If this ratio held going forward, it would mean that for every 44.4 gallons of water pumped out each year, about 1 gallon of aquifer storage would be lost.

During the recent drought many newspaper articles reported that there had been a sharp increase in the number of wells being drilled in the Central Valley, and that the depth of the wells had also significantly increased. This suggests an increase in the rate at which the water table is being lowered, which would lead to an increased rate of compaction. As the study notes, this is a loss that cannot be replenished; aquifer storage lost to compaction is gone forever.

Dry periods become more devastating when they occur during hot periods. One reason the recent drought in California was so devastating was because it was a hot drought. A recent study found that climate change has already raised the temperature in the state (as in Figure 3 above), and will continue to raise it further, to the point that every dry year is likely to be a hot drought. The report concludes that anthropogenic warming has substantially increased the risk of severe impacts on human and natural systems, such as reduced snowpack, increased wildfire risk, acute water shortages, critical groundwater overdraft, and species extinction.

The bottom line here is that we are talking about the effects of climate change. Climate means average patterns over long periods of time – 30 years at minimum. The current wet period represents only 1 winter. Just as one swallow doesn’t make a summer, so one wet winter doesn’t make a climate trend. For that matter, neither do 5 dry years. However, California’s increase in temperature is a long-term change that does make a climate trend, and every indication suggests it will only increase more.

My conclusion is that this wet winter not withstanding, the concerns I voiced in 2015 over California’s water supply remain valid. As time passes, California will face increasing challenges meeting the demand for water (see here). The state will be unable to secure large new sources of surface water or ground water (see here), and will have to construct large, expensive desalination plants (see here). There will be sufficient water to supply human consumption if it is properly allocated (see here), but water available to agriculture will be reduced, resulting in a decline in California’s agricultural economy (see here). That loss, plus the cost of the desalination plants, will impact California’s economy (see here), as well as the food supply for the entire country.

[In the above paragraph I have referenced several of the posts in my 2015 series Drought in California. If you are interested in the topic, you should read the series sequentially, beginning with Drought in California Part 1: Introduction.]


California Department of Water Resources. 2015. California Climate Science and Data for Water Resources Management. Downloaded 4/6/2017 from http://www.water.ca.gov/climatechange/docs/CA_Climate_Science_and_Data_Final_Release_June_2015.pdf.

Diffenbaugh, Noah, Daniel Swain, and Danielle Touma. 2015. “Anthropogenic Warming Has Increased Drought Risk in California.” Proceedings of the National Academy of Sciences. Downloaded 3/30/2017 from http://www.pnas.org/content/112/13/3931.

National Centers for Environmental Information. “California, Average Temperature, December-March, 1896-2016” Graph generated and downloaded 4/13/2017 at https://www.ncdc.noaa.gov/cag/time-series/us.

Smith, R.G., R. Kinght, J. Chen, J.A. Reeves, H.A. Zebker, T. Farr, and Z. Liu. 2016. “Estimating the Permanent Loss of Groundwater Storage in the Southern San Joaquin Valley, California.” Water Resources Research, American Geophysical Union. 10.1002/2016WRO19861. Downloaded 3/30/2017 from http://onlinelibrary.wiley.com/doi/10.1002/2016WR019861/full.

California Drought Emergency Officially Over

Gov. Jerry Brown officially declared California’s drought emergency over on Friday, April 7. It was a fitting ending to one of the worst episodes in California’s drought-laden history.

Or was it? The next two posts update California’s water situation. This one focuses on the current short-term situation. The next one focuses on the future, with an eye toward the future impact of climate change. I have personal reasons for following California’s water situation – I have family living there. But in addition, California is the most populous state in the Union, it has the largest economy of any state, and the state grows a ridiculously large fraction of our food. What happens in California affects us here in Missouri.

Figure 1. California Snowpack, 3/31/2017. Source: California Department of Water Resources.

Is the short-term drought truly over? Yes, I think so. The vast majority of California’s precipitation falls during the winter, and the snowpack that builds up in the Sierra Nevada Mountains serves as California’s largest “reservoir.” As it melts, it not only releases water that represents about 30% of the state’s water supply, but it also feeds water into the underground aquifers that provide groundwater to much of the state. Thus, the size of the snowpack is the most important factor in determining California’s water status. California measures the water content of the snowpack electronically and manually. The measurements around April 1 are considered the most important, as that is when the snowpack is typically at its largest. Figure 1 shows the report for this year. Statewide, the water content of the snowpack was 164% of average for the date, almost 2/3 larger than average. The water content was significantly above average in all three regions of the snowpack, North, Central, and South.



I follow the snow report at Mammoth Mountain Ski Resort to provide a specific example of the snow conditions. Figure 2 shows that through March, Mammoth received over 500 inches of snow, one of the highest totals in the record going back to 1969-70. The column for 2016-17 has very large blue and orange sections, indicating that the majority of the snow fell in January and February. Figure 3 confirms the impression. It charts the amount of snowfall at Mammoth during each month of the 2016-17 snow season, and compares it to the average for that month across all years. You can see that both January and February were monster snow months, especially January. By March, snowfall had already fallen below average. I wouldn’t make too much of this fact, one month doesn’t make a trend.

Figure 2. Source: Mammoth Mountain Ski Resort.

Figure 3. Data source: Mammoth Mountain Ski Resort.











Figure 4. Source: California Data Exchange Center.

California also stores water in man-made reservoirs. Figure 4 show the condition of 12 especially important ones on March 31. Most were above their historical average for that date, and many were approaching their maximum capacity. Those who follow this blog know that the Oroville Reservoir actually received so much water that it damaged both the main and emergency spillways, threatening collapse of the dam and requiring evacuation of thousands of people down stream. (See here.)







Figure 5. Elevation of the Surface of Lake Mead. Source: water-data.com.

In addition, Southern California receives the lion’s share of water drawn from the Colorado River, thus the status of Lake Mead, the largest reservoir on the Colorado, is important to the state. A study in 2008 found that there was a 50% chance the reservoir would go dry by 2021. On March 31, Lake Mead was at 1088.26 feet above sea level. (This doesn’t mean there were that many feet of water in the reservoir, Hoover Dam isn’t that tall. Rather, it represents how many feet above sea level the surface of the water was. Lake Mead’s maximum depth is 532 feet.) The current level represents 41.38% of capacity. Figure 5 shows the level of the lake over time. You can see that the line tends to go up with the spring snowmelt, and down during the rest of the year. This year it is up very slightly year-over-year, but the trend has been relentlessly down since 2000.

The conclusion seems inescapable: for this year at least, California has plenty of water. The short-term drought is over. One year doesn’t make a climate trend, however. In the next post I will consider the implications of this wet winter for California’s water situation going into the future.


Barnett, Tim, and David Pierce. 2008. “When Will Lake Mead Go Dry?” Water Resources Research, 44, W03201. Retrieved online at http://www.image.ucar.edu/idag/Papers/PapersIDAGsubtask2.4/Barnett1.pdf.

CA.GOV. Governor Brown Lifts Drought Emergency, Retains Prohibition on Wasteful Practices. Viewed online 4/10/2017 at https://www.gov.ca.gov/home.php.

California Data Exchange Center. Conditions for Major Reservoirs: 31-Mar-2017. Viewed online at http://cdec.water.ca.gov/cdecapp/resapp/getResGraphsMain.action.

California Department of Water Resources. Snow Water Equivalents (inches) for 3/30/2017. Viewed online 3/31/2017 at http://cdec.water.ca.gov/cgi-progs/snowsurvey_sno/DLYSWEQ.

Mammoth Mountain Ski Resort. Snow Conditions and Weather, Extended Snow History. Data downloaded 4/2/2017 from http://www.mammothmountain.com/winter/mountain-information/mountain-information/snow-conditions-and-weather.

water-data.com. “Lake Mead Daily Lake Levels.” Downloaded 4/5/2017 from http://graphs.water-data.com/lakemead/.