Damage from severe 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 spiked even higher 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 Lambert 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.
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.
I understand the trends in both figures this way: once in a while, Missouri has been struck with catastrophic weather events. They cause lots of deaths and a lot of damage, at a whole different scale from years with no catastrophic weather event. In years with no such event, weather-related deaths in Missouri have been around 40 or fewer, and injuries have been roughly 400 or fewer. Damages in such years have been about $150 million or less. In years with catastrophic weather events, the totals can be much higher.
2017 was a year in which Missouri saw no weather disasters that caused such high damages, or killed or injured so many people. That does not mean that Missouri was unaffected, however. The state was included in several billion-dollar weather disasters, the most costly of which was probably the flood of April 25-May 7. That was a historic flood for many of the communities that were affected.
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 only. In addition, for some reason the Missouri data for 2018 has not yet been posted.
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 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, which can cause widespread economic loss and from car crashes, which cause many injuries but fewer deaths.
Office of Climate, Water, and Weather Services, National Weather Service. 2016. Natural Hazard Statistics. Data for Missouri downloaded at various dates from https://www.nws.noaa.gov/om/hazstats.shtml#.
CPI inflation Calculator. 2019. 2017 CPI and Inflation Rate for the United States. Data downloaded 4/6/2019 from https://cpiinflationcalculator.com/2017-cpi-and-inflation-rate-for-the-united-states.
National Centers for Environmental Information. 2019. Billion-Dollar Weather and Climate Disasters: Table of Events. Viewed online 4/6/2019 at https://www.ncdc.noaa.gov/billions/events/US/1980-2018.
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.
The number of natural disasters in the USA in 2018 declined from 2017, and the amount of damage they did also declined.
Since 1980, there have been 241 severe weather and/or climate events in the USA that have caused damages exceeding $1.6 trillion dollars. The most important of these are the “billion-dollar disasters,” events that caused damages in excess of $1 billion. Figure 1 shows the data. The columns represent the number of events, with each color representing a different type of event. The black line represents a moving 5-year average number of events. They gray line represents the cost of damages, in billions of dollars.
In 2018, there were 14 billion-dollar disasters. That is more than double the long-term average. The 4 years with the most billion dollar disasters have all occurred in the last 8 years, and the last 3 years have ranked #1 (tie), #3, and #4. The last 3 years have been significantly higher than any other years except 2011. The increase comes primarily from severe storms, a category that excludes hurricanes and tropical cyclones, flooding and winter storms. These are tornadoes, thunderstorms, hail, and similar kinds of storms.
The estimated CPI-adjusted losses in 2018 were $91 billion. That’s quite a chunk of change, but it much less than the costs in 2017 ($312.7 billion), 2005 ($220.8 billion), or 2012 ($128.6 billion). 2017 was a terrible year (see here): Hurricanes Harvey, Irma, and Maria struck in 2017, and not only was it far-and-away the most costly year, it also tied for the highest number of disasters. Hurricane Katrina struck in 2005, and Hurricane Sandy struck in 2012. Hurricane Katrina is still the single event that caused more damage than any other, followed by Hurricanes Harvey and Maria. Last year, the most costly natural disaster was the series of wildfires in California, especially the Camp Fire. The fires caused an estimated $24 billion in damage.
Looking at Figure 1, starting somewhere around 2005, the number of billion-dollar disasters starts to trend upward. The amount of damage does, too, though the variation from year-to-year is much greater. The National Centers for Environmental Information, which keeps this data, factors the Consumer Price Index into it, so the change is probably not due to inflation.
Three factors probably account for most of the increase. First, climate change has caused an increase in the amount of energy in the atmosphere, energy that is available to power more and bigger storms. I once calculated that the increased radiative forcing from climate change was equal to the energy output of 1.6 million nuclear power plants. (See here) That’s a lot of energy available to power storms. Second, climate change has caused an increase in droughts throughout the western United States. Even in years like this one, when there has been an abundance of winter snow, the warm temperatures cause the snow to melt earlier in the spring, and they dry out the land faster during the summer. The result is a tinder box, perfect conditions for huge wildfires. And finally, we keep putting ourselves in harm’s way. Development has increased along the Atlantic and Gulf Coasts, where it is in the path of any hurricane that comes ashore. Development has also increased along the fringes of forests, where it is vulnerable to wildfire. And even in the middle of the country, sprawl has increased the built-up area, making tornadoes more likely to grind over it, as opposed to farmland.
Missouri was in the region damaged by some of the big weather events of 2018, so the next post will look at how we fared here in the Show Me State.
The National Centers for Environmental Information Billion-Dollar Weather and Climate Disasters portal has 5 pages available, and I used them all for this post: Overview, Mapping, Time Series, Summary Stats, and Table of Events. Downloaded and viewed online 4/3/2019 at https://www.ncdc.noaa.gov/billions.
This week I returned to St. Louis after being out of town for some time. I was greeted by a chorus of moans and groans about the horrible winter. Such kvetching! Of course, it is easy for somebody who has been in warmer climes to pooh-pooh the harshness of the winter back home. So, I decided to look and see what the statistics say, and since that is the focus of this blog, to do a post on what I found. I’m going to look at the winter in St. Louis and in Kansas City. For weather statistics, winter begins December 1st and ends February 28th (or 29th in leap years). I’m writing on February 21, so the data for this winter extends only through 2/20/2019. One final note: for grammatical reasons, in what follows, “normal” means historical average (mean).
The weather service office in each location keeps its data in slightly different formats, so I will do one, then the other.
Winter 2018-2019 in St. Louis
First, let’s ask if it has been excessively cold in St. Louis this winter. According to the National Weather Service, the record low temperature in St. Louis is -22°F, which occurred 1/5/1884. The observed low this winter was -6°F, on 1/20/19: cold, but nowhere near the record. For the 82 days from 12/1/18 through 2/20/19, on 57 of the days the record cold for that date has been -5°F or colder. This year, the low temperature has been nothing like that.
Well, you may say, perhaps the low temperature has not set records, but on most days it has been lower than normal. Figure 1 shows the daily observed low temperature compared to the normal low temperature for that date. The blue line shows the observed temperature for 2018-19, and the red line shows the normal low temperature for that date. The chart suggests that for much of the winter, the low temperature in St. Louis has actually been above normal. There have been a few cold outbreaks, but not record cold. The observed low temperatures over the period this winter have averaged 27°F. The normal low temperatures over the period have averaged 26°F. So guess what? The average low temperature this year has been about a degree above normal.
Well, you may say, perhaps the low temperature has not been excessively low, but the daily high temperature has been colder than usual. It’s not the deep lows of the night that has gotten to us, it’s the fact that it hasn’t warmed during the day. Figure 2 shows the daily observed high temperatures for 2018-19 (blue line), and the normal high temperature for those dates (red line). The chart shows that during the cold outbreaks noted above, the high temperature has, indeed, been cooler than normal. But much of the winter has also had highs above normal. Over the period, the observed highs this winter have averaged 43°F, while over the period, normal highs averaged 42°F.
Winter 2018-19 in Kansas City
The National Weather Service Office in Kansas City does not seem to publish a data series that contains information similar to the one published by the office in St. Louis. I have used, instead, data from the Climate-at-a-Glance data portal. This data does not include daily values, only monthly averages. Plus, it only extends through the end of January. January 19 was the coldest day of this winter, however, so it is included. Data collection began in 1972-73.
Figure 3 shows the data, with the blue line representing the observed values, and the gray line representing the average. The average temperature in Kansas City this winter was 2.5°F above normal.
The month of February to date can be included by using heating degree days instead of temperatures. Heating degree days are a measure designed to indicate to what degree the interior of buildings will require heating. To calculate it, average a day’s high and low temperature, then subtract the result from 65. This is how many heating degree days there were on that day. Now, to measure a period of time, simply sum the heating degree days for each day in the period.
The problem here is that the data in the climate summaries, where the heating degree data is published, use a different period to determine normal than does the data above. The data above uses values that run from when record keeping started to the current date. The climate summaries use data from 1981-2010. It was around 1980 that the effects of climate change really kicked in. This results in different estimates of “normal,” with the climate summary referencing only recent (warmer) history, and the other data referencing much longer (cooler) periods of time.
That said, it is the only way I can think of to include February for Kansas City in this discussion, so this is what the data shows:
|Observed Heating Degree Days||Normal Heating Degree Days||Difference|
|February 1-20 2019||731||657||
Looked at this way, it would appear that December created about 11% fewer degree days than normal, but January and February (to date) have created about 2% and 11% more, respectively. If you sum the differences for the 3 months together, then the winter to date has created 17 more heating degree days than normal, a trivial amount: in terms of heating degree days, Kansas City’s winter in 2018-19 should be understood to be roughly normal.
Now, none of this speaks to snow or blizzards. I understand that the winter storm at the end of January was a terrible event. In a similar fashion, I was in Hawaii when the winter cyclone came ashore in early February. I saw whole fields of banana trees leveled, just snapped off mid-trunk. On the top of Mauna Kea, the wind was recorded at 190+ mph. None of that changes the fact, however, that Hawaii has a lovely climate, and it was a wonderful place to visit (although too crowded these days, I’d say). Same in St. Louis. This blog is more concerned with statistical trends than individual events, and none of the statistics suggest that this has been, on average, a freakishly cold winter.
I read that people who believe in climate change are being peppered with the question “If the Earth is warming so much, how come it is so cold?” Nobody ever said that climate change would banish all cold, and the predictions are for more intense storms, just like the ones referenced above. But the real answer seems to be that it isn’t actually so cold, at least not here in Missouri. The whole question is nothing but phony baloney, at least here in Missouri.
NOAA National Centers for Environmental information, Climate at a Glance: U.S. Time Series, retrieved on February 21, 2018 from http://www.ncdc.noaa.gov/cag.
NOAA, National Weather Service, Kansas City/Pleasant Hill Forecast Office. 2/21/2019. Daily Climate Report. For this post, I used reports for 12/31/2018, 1/31/2019, and 2/20/2019. Viewed online 2/21/2019 https://w2.weather.gov/climate/index.php?wfo=eax.
NOAA, National Weather Service, St. Louis Forecast Office. 2/21/2019. Climate Graphs. Data retrieved on 2/21/2019 from https://www.weather.gov/lsx/cliplot.
2018 was the 3rd wettest year on record across the contiguous USA.
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 2018, the average precipitation across the contiguous USA was 34.62 inches, which was the 3rd highest amount in the record. Over time, precipitation seems to be increasing at about 0.18 inches per decade. The trend towards more precipitation is present in the Eastern Climate Region (+0.30 inches per decade), the Southern Climate Region (+0.24 inches per decade), and the Central Climate Region (+0.23 inches per decade). It is almost absent in the Western Climate Region, however (+0.02 inches per decade). In fact, 2018 was a below-average precipitation year in the West. (Except where noted, data is from the Climate-at-a-Glance data portal.)
(Click on figure for larger view.)
In Missouri, 2018 was the 41st wettest year on record, with 43.04 inches of precipitation. (Figure 2) This puts the year 2.54 inches 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.
Unlike 2016 and 2017, 2018 did not bring epic flooding to Missouri. Perhaps the most notable thing about Missouri precipitation in 2018 were two almost out of season snow events – one over the Easter weekend in April, and one in mid-November. The latter heralded what has been a very snowy winter so far in 2019 for Missouri and much of the Midwest.
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 24.83 inches of precipitation in 2017, some 5.82 inches above 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, this winter notwithstanding, 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 various demands? So far, these answers are not known. (For a more extended discussion, see here.)
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 big water year in 2017, 2018 returned to below-average precipitation. It was the 34th driest year on record, with precipitation 4.54 inches below average. (Figure 4)
As I reported previously, the California snow season started slowly this winter. It has been catching up, and is now nearly average for this date. The snowpack is above average in the Colorado River Basin above Lake Powell, the other major source for California’s water. The snowpack is 110% of the average for this date. (National Resource Conservation Service, 2/14/2018).
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.
2018 was the 4th warmest year on record globally, and the 14th warmest for the contiguous USA.
Figure 1 shows the average annual temperature for the Earth for each year from 1880-2018. 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 Fahrenhiet 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. (All data is from NOAA, Climate at a Glance.) 2016 was the highest on record, and 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 0.17°C per decade (0.30°F).
(Click on chart for larger view.)
Figure 2 shows the average yearly temperature for the contiguous United States from 1895 to 2018. 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. 2018 was the 14th highest in the record at 54.58°F. The 4 highest readings have all come within the last decade. Over the whole series, the average temperature has increased 0.15°F per decade. Since 1970, however, the rate has increased substantially.
Figure 3 shows the average temperature across Missouri for 2018. Across the state, it was the 35th warmest year on record, with an average temperature of 55.2°F. In Missouri, the warming trend from 1930-1950 was more marked than it was nationally; across the whole time period, the trend has been for a 0.1°F increase in temperature each decade. As was the case nationally, since 1970 the increase has accelerated.
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 slightly above average for this region. This region has been warming at a rate of 0.2°F per decade over the whole period, and, since 1970, the rate has accelerated substantially.
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 3rd warmest year in the record, with an average temperature of 60.2°F. California has been warming at a rate of 0.2°F each decade. Since 1970 the rate of increase has accelerated substantially.
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. Retrieved on February 1, 2019, from http://www.ncdc.noaa.gov/cag.
Followers of this blog know that I usually report on the snowpack conditions in California once or twice during the winter. I do this because I have family living in California, and because California constitutes an incredibly large percentage of this nation’s economy, and because it provides an incredibly large percentage of the fruits and vegetables we eat.
California depends on its snowpack for about 30% of its water supply. Climate change will reduce the California snowpack by as much as 40%, it is projected, putting the state’s water supply at risk. The snowpack is projected to decline mostly because the increased temperature will cause precipitation to fall as rain instead of snow, and because it will cause increased melting during the winter months.
The snow year got off to a slow start in California this year. The January 24 measurements showed the snowpack at 56-63% of average for that date, depending on which hydrologic region was measured. (See Figure 1.)
(Click on figure for larger view.)
The snowpack is below average despite the fact that California has had significant precipitation. November and December were slow, but at Mammoth Mountain, a ski resort located in the Sierra Nevadas, they have had 93 inches of snow this January. That puts the total for the winter within 2 inches of average for this date, and the month still has 4 days to go as I write.( See Figure 2.)
Because California receives most of its water during the winter, but needs it most during the summer, the state operates many reservoirs. The water content of the most important are shown in Figure 3. The Lake Shasta, Trinity, and Oroville Reservoirs are the three largest, and thus, the most important. In general, the reservoirs appear to be close to normal levels for this time of year. The one exception is the Oroville Reservoir, which is at 39% of capacity. This reservoir was severely damaged in 2017, when storms caused emergency releases, which eroded away major portions of the dam. Repairs were completed last fall, but the dam has yet to refill. Whether it will ever refill given California’s reduction in snowpack is an interesting question to which I don’t know the answer. Oroville is the major water source for the California State Water Project, and, thus, it is important.
The Colorado River is another important source of water for California, and Lake Mead is the principal reservoir at which its level is measured. It is at 1085.21 ft. above sea level, or 40% of its capacity. For this date the average is 1159 ft. above sea level, and the historical low was 1083.46 ft. above sea level, reached in 2016. Lake Mead can be recharged with water from Lake Powell, and that reservoir is also at 40% of capacity. It is usual for these reservoirs to be low during the late fall, and then recharge during the winter. However, Lake Mead continues to flirt with historical lows and with the level at which mandatory water restrictions go into effect.
The bottom line here is that California’s water supply continues to be below historical levels, though not quite as low as during the terrible drought a few years ago. As of right now, signs do not point to a severe water crisis this year, but the state continues to walk a rather fine line. Should drought recur, a severe crisis is likely to occur..
Alexander, Kurtis. 2018. “Oroville Dam Fixed and Ready to Go, Officials Say – But at a Big Price.” San Francisco Chronicle. 10/31/2018.
California Data Exchange Center. California Snowpack Water Content, January 24, 2019, Percent of April 1 Level. Downloaded 1.27.2019 from https://cdec.water.ca.gov/reportapp/javareports?name=PLOT_SWC.pdf.
California Department of Water Resources. Current Reservoir Conditions. Downloaded 1/27/2019 from http://cdec.water.ca.gov/reportapp/javareports?name=rescond.pdf.
Lake Mead Water Database. Viewed online 1/27/2019 at http://lakemead.water-data.com.
Mammoth Mountain Ski Resort. Snow & Weather Report. Viewed online 1/27/2019 at https://www.mammothmountain.com/winter/mountain-information/mountain-information.
The last post reported on 33 climate trends discussed in “State of the Climate 2017,” a report published in the Bulletin of the American Meteorological Society. This post characterizes the 2017 climate in the United States. Be sure to catch that this is for 2017, not 2018, the year just ended. In what follows, “CONUS” means the continental United States. All anomalies compare to the 1981-2010 average.
The annual average temperature in 2017 for the contiguous United States (CONUS) was 12.5°C or 1.0°C above the 1981–2010 average—its third warmest year since records began in 1895, 0.2°C cooler than 2016 and 0.4°C cooler than 2012. Figure 1 shows a map of 2017 temperature anomaly across the United States. Every state was warmer than average except for Washington. Most of Missouri was 1.0-1.5°C warmer than average (1.8-2.7°F). A few areas were even warmer, but the map isn’t sufficiently detailed to determine for sure which areas they were.
Averaged nationally, precipitation was 104% of average, making 2017 the 20th wettest year in the record. The pattern was variable, however, as shown in Figure 2. In particular, winter precipitation was higher than average, with Nevada and Wyoming each having the wettest winters on record. The California mountains were wetter than average (I reported on the large snowpack in the winter of 2017 in previous posts). So was eastern Colorado-New Mexico. On the other hand, much of the Southwest and the northern Plain States were in drought. It was also dry along the Mississippi River from the Missouri Bootheel into central Iowa.
There were 16 weather-related events in 2017 which resulted in damage of more than $1 billion. That tied with 2011 for the highest number of billion-dollar disasters. The total damages they caused was $306 billion, a new record. Figure 3 shows a map of where they were roughly located. There were three major hurricanes across the southern United States, plus catastrophic fires in California and other western states. Missouri and Arkansas were affected by flooding in late April-early May 2017.
Missouri had 13 fatalities and 155 injuries from weather-related disasters in 2017, and a total of $156.20 million in damages. There have been many years when the Missouri’s weather-related damage has been below $100 million, but in 2011 it was over $3.4 billion.
Blunden, J., D. S. Arndt, and G. Hartfield , Eds., 2018: State of the Climate in 2017. Bull. Amer. Meteor. Soc., 99 (8), Si–S332, doi:10.1175/2018BAMSStateoftheClimate.1. Downloaded 12/15/18 from https://www.ametsoc.org/index.cfm/ams/publications/bulletin-of-the-american-meteorological-society-bams/state-of-the-climate.
Office of Climate, Water, and Weather Services, National Weather Service. 2016. Natural Hazard Statistics. Data downloaded 2/10/16 from http://www.nws.noaa.gov/om/hazstats.shtml#.
Recent weeks have been very active for tropical storms. At one time in the Atlantic, there were 3 hurricanes (Florence, Helene, and Isaac) and 2 tropical storms (Gordon and Joyce). In the Eastern Pacific, August saw 4 tropical cyclones active at the same time (Hector, Kristy, John, and Lleana). and in September, Hurricane Hector and a new storm, Hurricane Olivia, impacted Hawaii. In the Western Pacific there have been 28 named storms. One of them, Super-Typhoon Mangkhut, caused extensive damage in the Philippenes.
Is this normal, or are tropical storms getting worse?
Tropical cyclones are rotating, organized storm systems that originate over tropical or subtropical waters. They have a center of low pressure around which they rotate that can develop into an “eye” if the storm is sufficiently intense and well organized. The thunderstorms tend to get organized into bands of thunderstorms that spiral out from the center. Even outside the thunderstorms, however, they have high sustained winds. In the Northern Hemisphere, they rotate counter-clockwise. In the Southern Hemisphere, they rotate clockwise.
Tropical cyclones are classified by the speed of their winds:
- Tropical Depressions have maximum sustained winds of 38 mph or less.
- Tropical Storms have maximum sustained winds of 39 to 73 mph.
- Hurricanes have maximum sustained winds of 74 mph or higher. In the Western Pacific, hurricanes are called typhoons. In the Indian Ocean and Southern Pacific, they are called cyclones.
- Major Hurricane have maximum sustained winds of 111 mph or higher.
Hurricanes are further classified according to the Saffir-Simpson Hurricane Wind Scale:
- Category 1: winds 74-95 mph., capable of causing damage even to well-constructed wood frame homes.
- Category 2: winds 96-110 mph., capable of causing damage to roofs and siding, blowing shallowly rooted trees over, and causing power loss.
- Category 3 (major hurricane): winds 111-129 mph., capable of causing structural damage to even well-built homes, snapping or uprooting lots of trees, and causing power outages that last for days.
- Category 4 (major hurricane): winds 130-156 mph., capable of causing catastrophic damage, ripping whole roofs off houses or blowing down walls. Regions impacted may be uninhabitable for weeks or months.
- Category 5 (major hurricane): winds 157 mph. or higher, capable of destroying most houses, blowing down most trees, cutting off access to whole regions, and making whole regions uninhabitable for weeks or months.
Tropical cyclones generally originate near the equator. Figure 1 shows the major regions where tropical cyclones tend to form, and their typical paths. I’m not sure what sends so many of them up the U.S. coast, rather than coming ashore. Perhaps it is the jet stream, or the Gulf Current, or the Mid-Atlantic High.
Figure 2 divides the year into 10-day intervals, and counts the number of tropical storms, hurricanes, and major hurricanes that form in the Atlantic Basin per 100 years during each interval. August and September are “hurricane season,” and the 10 days from September 10-19 are the peak. This chart would seem to indicate that during that interval, between 90 and 100 tropical storms originate every 100 years in the Atlantic Basin. That averages out to about 0.9-1.0 per year. Thus, it would appear that the last several weeks have been unusually active.
Figure 3 shows the number of tropical storms, hurricanes, and major hurricanes that have formed in the Atlantic Basin annually since 1851. The blue area shows the number of tropical storms, the red area shows the number of hurricanes, and the green area shows the number of major hurricanes. To each series I have fitted a polynomial regression line.
First, the variation between years is large for all of the series. Second, there are more tropical storms than hurricanes, and more hurricanes than major hurricanes. Third, all three series show an increasing trend over time. There are more tropical storms than there used to be, more hurricanes, and more major hurricanes. HOWEVER, in viewing these trends, one must keep in mind that today we have weather satellites, air travel, and a good deal more shipping density across the Atlantic Ocean. It is quite possible that some storms went undetected or unmeasured in the past, but that is no longer the case. Thus, the observed change could easily be due to better observations, not a real increase in the number of storms. I don’t have the ability to make that correction, but The Fifth Assessment Report of the Intergovernmental Panel on Climate Change concluded that evidence for an increase in the number of tropical cyclones is not robust.
As noted above, tropical cyclones can form in 8 basins around the world. One might ask which produces the most severe storms? Figure 4 shows the data. All of the basins have produced storms with sustained winds above 150, but the highest ever recorded was 215 mph. in Hurricane Patricia in the Eastern Pacific in 2015. In terms of lowest central pressure, the lowest ever recorded was in Typhoon Tip in the Western Pacific in 1979.
One might also ask which basin produces the most severe storms. Record keeping began in a different year in each basin, however, there appears to be a clear answer: the Western Pacific. Counting only storms with a minimum central pressure below 970 kPa, this basin has produced more than twice as many as any other basin.
Large cyclonic storms most often form in the tropics during hurricane season, but they don’t have to. For instance, the so-called “Perfect Storm” (they made a movie about it starring George Clooney) was a 1991 storm that formed in the Atlantic off the coast of Canada on October 29. It developed into a Category 1 hurricane, with a well defined eye, not dissipating until after November 2. Similarly, the remnants of Tropical Storm Rina (2017) travelled north across the Atlantic, crossed the British Isles, and crossed Central Europe. Entering the Mediterranean Sea, it re-strengthened into a tropical storm, now called Numa, which developed an eye and other characteristics typical of a hurricane. It’s strength peaked on November 18, with maximum sustained winds of 63 mph., not quite hurricane strength, but close.
Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
NASA Space Place. 2018. How Do Hurricanes Form. Downloaded 9/18/2018 from https://spaceplace.nasa.gov/hurricanes/en.
National Oceanic and Atmospheric Administration. 2018. Tropical Cyclone Climatology. Viewed online 9/18/2018 at https://www.nhc.noaa.gov/climo.
Wikipedia contributors. (2018, July 21). Cyclone Numa. In Wikipedia, The Free Encyclopedia. Retrieved 19:26, September 18, 2018, from https://en.wikipedia.org/w/index.php?title=Cyclone_Numa&oldid=851259614
Wikipedia contributors. (2018, September 14). List of the most intense tropical cyclones. In Wikipedia, The Free Encyclopedia. Retrieved 22:23, September 18, 2018, from https://en.wikipedia.org/w/index.php?title=List_of_the_most_intense_tropical_cyclones&oldid=859553932.
I’ve reported on drought in the American West many times in this blog. What about the country as a whole?
One way of looking at this question is by asking each month how much of the country has been very dry, and how much as been very wet? By very dry, I mean that the amount of precipitation for that month falls in the lowest 10% for that month in the historical record. By very wet, I mean that the amount of precipitation for that month falls in the highest 10% for that month.
The National Oceanic and Atmospheric Administration keeps this data. They measure the precipitation in every county in the country, and calculate what percent of the country was very dry, and what percent was very wet. They have data for every month going back to January of 1895.
Figure 1 shows the monthly data for every month all the way back to January, 1895. Blue bars represent the percentage of the country that is very wet. Red bars represent the percentage that is very dry. (To keep the blue and red bars from obscuring each other, I multiplied the dry percentage by -1, thereby inverting it on the chart.) I dropped trend lines on both data series. As you can see, there is considerable variation from year-to-year. There is a slight trend – hardly noticeable – towards more very wet months and fewer very dry months. But it is small, and the yearly variation is much greater than the trend.
Figure 2 shows the same data, but it beings in January, 1994.. I constructed this chart to see whether the most recent 25 years look different than the record as a whole. Again, blue bars represent very wet months, and the red bars represent very dry ones. I dropped linear trend lines on both data series, as before. The yearly variation is again larger than the trends. There appears to be virtually no trend in the number of very dry months. There is a small trend towards increasing number of very wet months. It appears a bit larger than did the one for the whole time period, but even so, it is tiny compared to the yearly variation.
It’s a bit hard to read the two data series on opposite sides of the zero line, so I constructed Figure 3. For each month it shows the percentage of the country that was very dry minus the percentage that was very wet. By doing my subtraction that way, numbers above zero mean that more of the country was very dry than very wet, and numbers below zero mean that more of the country was very wet. I dropped a linear trend on the data (red), and I also dropped a 15-year moving average on it. The chart shows that, as we saw in Figure 1, there is a slight trend towards fewer very dry months and more very wet ones. The variation is much larger than the trend, whether one looks at the monthly data, or the yearly.
This data differs from other drought data I report. Those reports focus on the Palmer Drought Severity Index, an index intended to represent soil moisture. Soil can dry out because there is little overall precipitation, or because there are longer periods between precipitation events, or because the temperature is warmer. This data would tend to indicate that regions of the country with very little precipitation may be decreasing very slightly, very slowly. Regions with very much precipitation may be increasing. This trend would be consistent with consensus predictions regarding climate change, where overall precipitation is not expected to change, but the number of heavy precipitation events is expected to increase.
National Centers for Environmental Information, National Oceanographic and Atmospheric Administration. U.S. Percentage Areas (Very Warm/Cold, Very Wet/Dry). Downloaded 9/1/2018 from https://www.ncdc.noaa.gov/temp-and-precip/uspa.
Revision: This is a revision of the post that appeared yesterday, 8/2/18. The Drought Monitor map issued 7/31/18 shows drought intensifying in Missouri, and extending to include most of the state. In this revision, I’ve replaced the map with the newer one, and I’ve revised the text to include the new information.
Drought has one again gripped the American West and Southwest. Unfortunately, the wet winter of 2017 turned out to be a one-year reprieve. Perhaps the coming winter will be wet again, but for now, the regions are once again dry – in some cases, as dry as they have ever been since record-keeping began.
Figure 1 shows the U.S. Drought Monitor for July 17, 2018. This map shows the Palmer Drought Severity Index for the United States. White areas are not in drought, colored areas are, and the darker the color, the worse the drought. It is easy to see that an “exceptional drought” has gripped portions of the Southwest, centered on the Four Corners Area where Colorado, New Mexico, Arizona, and Utah meet. Though the drought is most severe there, it has gripped much of the entire western United States.
Drought is primarily about soil moisture. Without moisture in the soil, crops wither and drinking water sources dry up. It is not feasible, however, to directly measure soil moisture across the entire country. The Palmer Drought Severity Index computes an estimate of soil moisture using temperature and precipitation data, and is the primary measure of drought used by the National Oceanographic and Atmospheric Administration.
Figure 2 shows the PDSI in June for the Southwest Climate Region (Arizona, Colorado, New Mexico, and Utah) from 1895 to 2018. Green columns represent years when it was wetter than average in June, orange columns when it was dryer than average. It is easy to see that green columns cluster to the left of the chart, and orange ones cluster to the right. In fact, of the most recent 19 years, 16 have been drier than average. This year, June was the second driest in the record, virtually as dry as it has ever been since record keeping began. The blue line shows the trend: the PDSI has decreased -0.23 per decade on average.
Ever since I wrote an extended series of posts on drought in California in 2015, this blog has followed the drought situation there. Plentiful snow during the winter of 2017 brought welcome relief, but the winter of 2018 was a big disappointment. Precipitation was below average, and the snowpack peaked well below normal (see here).
As Figure 3 shows, California has not escaped the drought gripping most of the West. The most extreme drought is in the southeastern corner of the state. That is where the Imperial Valley is located, a region that supplies us with many of our fruits and vegetables. The farms there are mostly irrigated with water from the Colorado River, so local drought there is not a terrible worry for us here in Missouri. More on the Colorado River below, however.
Figure 4 shows that the PDSI for the state as a whole for June 2018, indicates a severe drought, but not an extreme one. The trend over time is clearly downward, however, and the continued dryness represents a long-term threat to the state’s water supply.
As Figure 5 shows, California’s reservoirs are moving into deficit. They have been fuller than average for most of the time since the winter of 2017, but now three of the biggest and most important, Trinity Lake, Lake Shasta, and Lake Oroville, are below average for this date. In the chart, the yellow bars represent the maximum capacity of each reservoir, the blue bars the current level, and the red line the average for this date. Lake Oroville has not yet fully recovered from the near disaster in 2017 that caused managers to lower the lake level to prevent a collapse of the dam(see here).
Readers who have been following this blog know that California, Arizona, Nevada, Utah, New Mexico, and even Mexico depend on water from the Colorado River, and that Lake Mead is the large reservoir that holds the water for all of those states. You also know that water withdrawals from Lake Mead have exceeded inputs for many years, and the level of water in the lake has been relentlessly dropping. One study went so far as to predict that Lake Mead had a 50% chance of going dry by 2021. (Barnett and Pierce, 2008. See here for a fuller discussion California’s water resources.) Figure 6 shows the level of the lake for the past 3 years. The green line shows 2016, the red line 2017, and the blue line the year-to-date in 2018. Notice that the chart begins October 1, which is the official start of the water year. The wet winter of 2017 replenished the lake a little bit, but you can see that the current drought is causing it to drop again. Lake Mead is only 38% full, and Lake Powell, the large reservoir upstream from Lake Mead, is only 51% full. These low levels do not represent an immediate existential threat, but if dry conditions persist, they will before too many years pass.
The most important source of Missouri’s water is the Missouri River (see here). As Figure 7 shows, precipitation in the Northern Rockies and Plains Climate Region was slightly above average for the first 6 months of 2018. Statistics for the reservoirs along the Missouri show that they are at or near maximum storage. In fact, since part of their mission is flood control, several of them are higher than desired for that purpose. (U.S. Army Corps of Engineers, 2018)
Going back to Figure 1, however, you can see that the drought over the West has expanded to include Missouri, and it is especially severe in the northwestern part of the state. In St. Joseph, for instance, July brought 1.10 inches of rain, compared to 5.19 inches in an average July. In addition, since January 1, St. Joseph experienced 326 more heating degree days than average, an increase of 43%. That translates, on average, to a daily increase 1.8°F. (I arrived at this number by dividing the excess in heating degree days by the number of days.) Drought is as much a result of increased temperature as it is of reduced precipitation. Even if precipitation remains constant, increased temperature causes the ground to dry out more quickly, intensifying drought.
Because the reservoirs along the Missouri are relatively full, this drought will impact agriculture more than it will impact drinking water, unless your drinking water comes from wells. Drought can impact the availability of ground water to seep into wells, especially if they are shallow.
Climate projections for Missouri do not project a large decrease in precipitation. They tend to project that precipitation will remain about the same, or possibly increase slightly. Temperature, however, will rise, leading to a potential increase in the frequency of damaging drought. The real concern, however, is that the drought in the American West might not be not a temporary weather phenomenon, but, instead, a permanent change in climate. Modelers predict that climate change will cause just such a change Could it be occurring already?
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.
Lake Mead Water Database. 2018. Lake Mead Daily Water Levels, Last 3 Water Years. Downloaded 7/19/2018 from http://graphs.water-data.com/lakemead.
National Oceanographic and Atmospheric Administration. 2018. Climate-at-a-Glance. Data downloaded 2018-07-19 from https://www.ncdc.noaa.gov/cag.
Riganti, Curtis. 2018. U.S. Drought Monitor, July 17, 2018. National Drought Mitigation Center. Downloaded 7/19/2018 from http://droughtmonitor.unl.edu.
U.S. Army Corps of Engineers, Missouri River Basin Water management. 2018. Mainstem and Tributary Reservoir Bulletin, 7/18/2018. Viewed online 7/19/2018 at http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/MRBWM_Reservoir.pdf.