Weather Extremes

The Amazing June Heat Wave of 2012. Part 1: The West and Plains June 23-27

By: weatherhistorian, 8:17 PM GMT on June 29, 2012

The Amazing June Heat Wave of 2012. Part 1: The West and Plains June 23-27

One of the most intense heat waves in U.S. history has enveloped portions of the western plains and Midwest and has now spread eastward. All-time heat records have fallen at a number of significant weather stations. And it is still just June. Is this a prelude for the coming summer or just a flash in the pan?

NOTE: This is Part 1 of two blogs, Part 2 will focus on the heat wave in the eastern third of the country and will be posted on Sunday, July 1st.

The Set Up for the Heat Wave

June had been a warm but not excessively so month until around June 20-23rd when an upper level high pressure dome that had been centered over the Baja of Mexico began to move/expand northeastward and strengthen dramatically. Between June 23 and June 27 this dome remained nearly stationary over the southern plains and maintained its strength.



The water vapor image for 3Z on June 23 shows a deep trough over the Pacific Ocean west of California amplifying the high pressure ridge over the southwest and southern plains. Image from UNYSYS GOES West satellite.

The daily 500-millibar upper analysis charts for this period are shown below:



500 mb heights at 12Z on June 20, 2012. Image from NOAA Daily Weather Map.



500 mb heights at 12Z on June 22, 2012. Image from NOAA Daily Weather Map.



500 mb heights at 12Z on June 25, 2012. Image from NOAA Daily Weather Map.

The air aloft became so abnormally warm that the NWS office in Dodge City focused on how intense the air aloft was in their daily discussions. At the 850 millibar level (about 5000’) the temperature was averaging an amazing 30°C (86°F) at the 5 a.m. (12Z) observation times on June 23-27!

The heat at surface level reached its greatest extent on June 26th, although the period of all-time records broken ranged from June 23 to June 27.

Here is a surface temperature map for 5p.m CST time on June 26:



Surface temperature map for 5 p.m. CST on June 26th when the heat wave was at its peak. Note that the white shaded region represents temperatures of 105°+ and the white outlined area inside the white region represents 110°+. Map from UCAR.



Maximum and minimum temperatures for select stations on June 26th. NOAA Daily Weather Map. An interesting fact the exemplifies the magnitude of the Pacific trough and plains ridge is that it was snowing in the mountains along the border of Idaho and Montana above 7000' at the same time it was 111° in Miles City, Montana.

Records set in the West and Plains June 22-27

COLORADO

Perhaps the single most impressive record broken of all was the 114°F recorded at Las Animas, Colorado on June 23rd. This tied the hottest temperature ever measured during any month anywhere in the entire state of Colorado (114° has been recorded in the past at Las Animas on July 1, 1933 and Sedgwick on July 11, 1954).

All-time heat records (for any month) were also set or tied in Denver with 105° on both June 25 and June 26 (tied with 105° on July 20, 2005 and Aug. 8, 1878), Colorado Springs with 101° on June 26 (previous record of 100° set on five previous occasions including June 24 and June 25), Lamar hit 112° on June 27 (previous record 111° on July 13, 1934 and also on June 26, 2012). In far northeastern Colorado all-time heat records were also set at Yuma (111°) and Holyoke (110°) on June 27th. June all-time monthly heat records were set at virtually every site in the state east of the Rocky Mountain front range (like the 102°s at Fort Collins and Trinidad).

Denver reached 100°+ for a record tying five consecutive days June 22-16. Pueblo recorded six consecutive 105°+ days June 22-27, its longest streak of such heat on record (its maximum was 107° on June 24th, two degrees short of its all-time record of 109° and one degree short of its June record of 108° set on June 29, 1990).

The intense heat exacerbated the terrible wild fires in the Rocky Mountain foothill communities of Fort Collins, Boulder, and Colorado Springs where around 600 homes have been lost and at least two lives lost.

KANSAS

Dodge City recorded its all-time (any month) record high of 111° on June 27th (previous record of 110° set on 3 previous occasions including June 26, 2011 AND June 26, 2012!). This is a particularly significant measurement since Dodge City has one of the longest continuous periods of record in the U.S.: since September 1874. Hill City was the state’s hottest spot during the heat wave with 115° measured on both June 26th and June 27th. This was a monthly record for the site but not all-time (117° in July 1936). It was also just one degree shy of the Kansas state monthly all-time June heat record (116° at Hugoton on June 25, 1911). An unofficial 118° was reported from Norton Dam on June 27th by a RAWS site.

All-time records were broken or tied also at Colby (112°, old record 110° in 1953) and Tribune with 111° (a sort POR here).

Most locations in the western third of Kansas broke their all-time June monthly records such as Goodland’s 110° on June 24 and June 25 (old June record was 109° on June 18, 1936).

NEBRASKA

An all-time Nebraska state monthly heat record for June was set at McCook with 115° on June 26 (previous record was 114° at Franklin on June 26, 1936). This was also the all-time (any month) record for McCook. Benkelman reached an all-time high of 114°. Sidney also broke their all-time any month record with 111° the same day. Interestingly, the high temp in Sidney may have been the result of heat burst since the temperature rose from 102° at 3:52 p.m to 111° by 4:05 p.m (a 9° rise in 14 minutes!). Thunderstorms were in the vicinity. This broke the previous June monthly record by an astonishing 7°!

MONTANA

An all-time heat record (any month) was set at Miles City with 111° on June 26. However, this reading was made at the airport (POR 1937-current) whereas a temperature of 113° was recorded at the Miles City COOP downtown site on July 20, 1960 (POR 1893-1982). In any case, the 111° was just one degree short of the Montana state monthly June record (112° at Baker in June 2002).

NEW MEXICO

The excessive heat only affected the northeastern third of New Mexico.
Santa Fe and Tucumcari both came within 1° of their respective all-time heat (any month) records: Santa Fe 99° on June 23 and Tucumcari 108° on June 27. This was a June monthly record for Tucumcari, but Santa Fe has seen 100° on June 5, 2010.

Could this be the Beginning of Another ‘Summer of 1936'?

The only previous June heat waves in U.S. history that compare to the current one were those of 1934, 1936, and 1954. The summer of 1934 went on to be the warmest on record for the U.S. (74.6° June-August average) and July 1936 the single hottest month on record (77.4° average).

Ominously, some of the June records that have so far been set this month have eclipsed those of June 1934 and 1936 (1954 turned out be a summer of only slightly above long-term average normal temperature).

I’ll be posting part two of this blog (covering the heat records in the eastern third of the country set during the period of June 28-30) on Sunday July 1st.

Christopher C. Burt
Weather Historian

Heat Temperature

Updated: 8:14 AM GMT on July 01, 2012

Permalink

Thunderstorms: The ‘Stormiest’ Places in The U.S.A. and the World

By: weatherhistorian, 9:13 PM GMT on June 21, 2012

Thunderstorms: The ‘Stormiest’ Places in The U.S.A. and the World

June normally marks the beginning of the monsoon season in America’s Southwest and some areas may expect to see almost daily afternoon thunderstorms develop between now and September. These storms are the principle contributor to wild fires during the summer months in the western U.S. Here’s a summary of some of the ‘stormiest’ places in the country and world.




A severe thunderstorm bears down on a truck stop in central Nebraska. The storm produced a tornado shortly prior to the photo being taken. Photo by Mike Hollingshead. For amazing storm photos visit Mike’s web site.



U.S.A. Stormiest Places

There are two ways to determine which places in the U.S. experience the greatest number of thunderstorms. One is to count ‘thunderstorm’ days: the number days each year that thunder is heard at a particular weather station and 2) count the actual number of individual thunderstorms that occur at a weather site. There is a difference since some places, especially in Florida receive more than one thunderstorm in a single day. Cape Canaveral, for instance, once counted six separate thunderstorms in one day. For the sake of comparing one location to another I am going to use the number of ‘thunderstorm days’ criteria.



This map shows the actual number of thunderstorms reported each year on average, not thunderstorm days. Map from ‘Extreme Weather; A Guide and Record Book’ source of data from NCDC.



Here is an alternative view of U.S. thunderstorm activity that illustrates the number of lightning strokes recorded per square mile. Map from Visalia Lightning Detection Network.



This map shows, in a broad-brush fashion, the month of maximum thunderstorm activity by region. Map from ‘Extreme Weather; A Guide and Record Book’ source of data from NCDC.

It is probably not surprising that portions of Florida record the greatest number of thunderstorm days in the U.S. with as many as 100-130 storm-days a year in an area inland of the Gulf Coast stretching from the Everglades north to the city of Lakeland (about 30 miles inland from Tampa) being the area of greatest activity. Lakeland, Florida averages 100 thunderstorm days a year, the most of any significant city in the entire country. Tampa averages 78 thunderstorm days and Fort Meyers 92 (the 2nd highest number for any city after Lakeland). Below are a couple of tables listing the city’s with the most number of annual thunderstorm days and a list of some other major U.S. cities and their number of such days.





The other region that can contend (almost) with Florida and the immediate Gulf Coast of Alabama and Mississippi is a small area in northern New Mexico in the Sangre de Christo Mountains centered around the small town of Cimarron (elevation 6,400’) where thunderstorms occur about 110 days of the year. Not surprisingly, at one time a government lightning-research facility was located here. In July the area averages 30 thunderstorm-days, in other words virtually every day of the month.



In west-central New Mexico near the town of Quemado (an area that experiences frequent summer thunderstorms) the artist Walter de Maria installed a field of several acres of lightning rods as part of a conceptual art project in the 1970s. Photo from Walter de Mario web site.


Another small region in the Southwest that also averages a thunderstorm every day of the month during July are the Huachuca Mountains in extreme southeast Arizona (in fact July averages 32 thunderstorms, more than one a day!). These mountains record about 80-90 thunderstorm days a year. Tucson, which is located just 50-60 miles north of here is known as one of the best places in the world to view thunderstorms since it averages about 20 July t-storm days and has nearby mountains (Mt. Lemmon in particular) that offer superb viewing platforms. Tucson averages about 40 thunderstorm days a year.




Mt. Lemmon near Tucson, Arizona is a favorite haunt for storm photographers during the summer monsoon storm season. Photo y A.T. Willett.

An area along the central front range of Colorado averages as many as 80 thunderstorm days a year as evidenced by the average of 51 storm days a year in Colorado Springs (the highest figure for any major city in the West). Colorado, in fact, endured more lightning fatalities (39) than any state in the union out side of Florida (126) and Texas (52) for the period of record 1990-2003 (the latest POR for such data I can find). However, when the fatalities are weighted for population density, Wyoming is by far the deadliest with a death rate of 2.02 per million people compared to Florida’s 0.56 rate (which ranks 4th in this regard). After Wyoming, the next deadliest (deaths per million) states are Utah (0.70) and Colorado (0.65). Of course, this is a bit of a meaningless statistic since these western states host millions of tourists every summer. Wyoming, for instance, may be the least populated state in the union (about 400,000 residents) but it sees about 2 million summer visitors to its national parks like Yellowstone and the Grand Tetons during the summer months. Many of these are alpine climbers and backcountry trekkers. So, of course, they are subject to the storms that occur during the peak climbing and hiking months of the summer.





The maps above show the total number of deaths by lightning by state (top) and deaths ranked by number per million of residents (bottom). The period of record for both maps is 1990-2003. Source from Storm Data, NOAA.




Moments after this photograph was taken these two boys were struck by lightning and seriously injured. A nearby hiker was killed. They were posing for the shot on top of Moro Rock in Sequoia National Park in the Sierra of California during the summer of 1975. Photo by Mary McQuilken (sister of the two boys).


Stormiest Places in the World

The area that experiences the most thunderstorm days in the world is northern Lake Victoria in Uganda, Africa. In Kampala thunder is heard on average 242 days of the year, although the actual storms usually hover over the lake and do not strike the city itself. The reason for the incredible number of storms here is best summed up by F.E. Lumb in the British journal ‘Weather’:

Land-breeze convergence over the lake during the night releases latent instability of the moist lower layers of air over the lake which participate in the land breeze circulation, resulting in the development of cumulonimbus clouds and thunderstorms over the lake most nights of the year.

This is also likely the reason that a phenomenal number of thunderstorms develop over northern Maracaibo Lake in Venezuela, resulting in the famous ‘Catatumbo Lightning’ phenomena (named after the river that flows into the lake and where the storms are most frequent). It is estimated that storms develop on about 140-160 nights a year here providing extraordinary lightning displays.



A map of worldwide annual thunderstorm days. The table under the map lists the single most thunderstorm-prone towns and cities on earth. Map from ‘Extreme Weather: A Guide and Record Book’ and based on data from ‘The World Survey of Climatology’, Elsevier Publishing Comp.

At one time Bogor, Indonesia (a very large city near a volcano on Java Island) was reputed to have 322 thunderstorm days per year. This is an apocryphal number although storms do develop over the volcano just south of the city on an almost daily basis. Further inland the city of Bandung records an average of 218 thunderstorm days annually, the most for any site in Asia. The Congo River Basin of Africa averages as many as 228 thunderstorms days as is the case in the city of Bunia, Republic of Congo. In South America, the Amazon Basin reports up to 206 thunderstorm days at the town of Carauri. Australia’s stormiest location is Port George IV in Western Australia on the shores of the Timor Sea where 100 thunderstorm days a year are the norm.


And as a parting shot on the subject of thunderstorms…



A marvelous high definition photo pastiche (composed of 11 separate images) of a cumulonimbus cloud that produced golf ball-size hail three miles from this vantage point (undetermined location). Photo by Pat Kavanaugh.

Christopher C. Burt
Weather Historian

Thunderstorms

Updated: 4:29 AM GMT on June 22, 2012

Permalink

Thunderstorms: The ‘Stormiest’ Places in The U.S.A. and the World

By: weatherhistorian, 9:13 PM GMT on June 21, 2012

Thunderstorms: The ‘Stormiest’ Places in The U.S.A. and the World

June normally marks the beginning of the monsoon season in America’s Southwest and some areas may expect to see almost daily afternoon thunderstorms develop between now and September. These storms are the principle contributor to wild fires during the summer months in the western U.S. Here’s a summary of some of the ‘stormiest’ places in the country and world.



A severe thunderstorm bears down on a truck stop in central Nebraska. The storm produced a tornado shortly prior to the photo being taken. Photo by Mike Hollingshead. For amazing storm photos visit Mike’s web site.

U.S.A. Stormiest Places

There are two ways to determine which places in the U.S. experience the greatest number of thunderstorms. One is to count ‘thunderstorm’ days: the number days each year that thunder is heard at a particular weather station and 2) count the actual number of individual thunderstorms that occur at a weather site. There is a difference since some places, especially in Florida receive more than one thunderstorm in a single day. Cape Canaveral, for instance, once counted six separate thunderstorms in one day. For the sake of comparing one location to another I am going to use the number of ‘thunderstorm days’ criteria.



This map shows the actual number of thunderstorms reported each year on average, not thunderstorm days. Map from ‘Extreme Weather; A Guide and Record Book’ source of data from NCDC.



Here is an alternative view of U.S. thunderstorm activity that illustrates the number of lightning strokes recorded per square mile. Map from Visalia Lightning Detection Network.



This map shows, in a broad-brush fashion, the month of maximum thunderstorm activity by region. Map from ‘Extreme Weather; A Guide and Record Book’ source of data from NCDC.

It is probably not surprising that portions of Florida record the greatest number of thunderstorm days in the U.S. with as many as 100-130 storm-days a year in an area inland of the Gulf Coast stretching from the Everglades north to the city of Lakeland (about 30 miles inland from Tampa) being the area of greatest activity. Lakeland, Florida averages 100 thunderstorm days a year, the most of any significant city in the entire country. Tampa averages 78 thunderstorm days and Fort Meyers 92 (the 2nd highest number for any city after Lakeland). Below are a couple of tables listing the city’s with the most number of annual thunderstorm days and a list of some other major U.S. cities and their number of such days.





The other region that can contend (almost) with Florida and the immediate Gulf Coast of Alabama and Mississippi is a small area in northern New Mexico in the Sangre de Christo Mountains centered around the small town of Cimarron (elevation 6,400’) where thunderstorms occur about 110 days of the year. Not surprisingly, at one time a government lightning-research facility was located here. In July the area averages 30 thunderstorm-days, in other words virtually every day of the month.



In west-central New Mexico near the town of Quemado (an area that experiences frequent summer thunderstorms) the artist Walter de Maria installed a field of several acres of lightning rods as part of a conceptual art project in the 1970s. Photo from Walter de Mario web site.

Another small region in the Southwest that also averages a thunderstorm every day of the month during July are the Huachuca Mountains in extreme southeast Arizona (in fact July averages 32 thunderstorms, more than one a day!). These mountains record about 80-90 thunderstorm days a year. Tucson, which is located just 50-60 miles north of here is known as one of the best places in the world to view thunderstorms since it averages about 20 July t-storm days and has nearby mountains (Mt. Lemmon in particular) that offer superb viewing platforms. Tucson averages about 40 thunderstorm days a year.



Mt. Lemmon near Tucson, Arizona is a favorite haunt for storm photographers during the summer monsoon storm season. Photo y A.T. Willett.

An area along the central front range of Colorado averages as many as 80 thunderstorm days a year as evidenced by the average of 51 storm days a year in Colorado Springs (the highest figure for any major city in the West). Colorado, in fact, endured more lightning fatalities (39) than any state in the union out side of Florida (126) and Texas (52) for the period of record 1990-2003 (the latest POR for such data I can find). However, when the fatalities are weighted for population density, Wyoming is by far the deadliest with a death rate of 2.02 per million people compared to Florida’s 0.56 rate (which ranks 4th in this regard). After Wyoming, the next deadliest (deaths per million) states are Utah (0.70) and Colorado (0.65). Of course, this is a bit of a meaningless statistic since these western states host millions of tourists every summer. Wyoming, for instance, may be the least populated state in the union (about 400,000 residents) but it sees about 2 million summer visitors to its national parks like Yellowstone and the Grand Tetons during the summer months. Many of these are alpine climbers and backcountry trekkers. So, of course, they are subject to the storms that occur during the peak climbing and hiking months of the summer.





The maps above show the total number of deaths by lightning by state (top) and deaths ranked by number per million of residents (bottom). The period of record for both maps is 1990-2003. Source from Storm Data, NOAA.



Moments after this photograph was taken these two boys were struck by lightning and seriously injured. A nearby hiker was killed. They were posing for the shot on top of Moro Rock in Sequoia National Park in the Sierra of California during the summer of 1975. Photo by Mary McQuilken (sister of the two boys).

Stormiest Places in the World

The area that experiences the most thunderstorm days in the world is northern Lake Victoria in Uganda, Africa. In Kampala thunder is heard on average 242 days of the year, although the actual storms usually hover over the lake and do not strike the city itself. The reason for the incredible number of storms here is best summed up by F.E. Lumb in the British journal ‘Weather’:

Land-breeze convergence over the lake during the night releases latent instability of the moist lower layers of air over the lake which participate in the land breeze circulation, resulting in the development of cumulonimbus clouds and thunderstorms over the lake most nights of the year.

This is also likely the reason that a phenomenal number of thunderstorms develop over northern Maracaibo Lake in Venezuela, resulting in the famous ‘Catatumbo Lightning’ phenomena (named after the river that flows into the lake and where the storms are most frequent). It is estimated that storms develop on about 140-160 nights a year here providing extraordinary lightning displays.



A map of worldwide annual thunderstorm days. The table under the map lists the single most thunderstorm-prone towns and cities on earth. Map from ‘Extreme Weather: A Guide and Record Book’ and based on data from ‘The World Survey of Climatology’, Elsevier Publishing Comp.

At one time Bogor, Indonesia (a very large city near a volcano on Java Island) was reputed to have 322 thunderstorm days per year. This is an apocryphal number although storms do develop over the volcano just south of the city on an almost daily basis. Further inland the city of Bandung records an average of 218 thunderstorm days annually, the most for any site in Asia. The Congo River Basin of Africa averages as many as 228 thunderstorms days as is the case in the city of Bunia, Republic of Congo. In South America, the Amazon Basin reports up to 206 thunderstorm days at the town of Carauri. Australia’s stormiest location is Port George IV in Western Australia on the shores of the Timor Sea where 100 thunderstorm days a year are the norm.

And as a parting shot on the subject of thunderstorms…



A marvelous high definition photo pastiche (composed of 11 separate images) of a cumulonimbus cloud that produced golf ball-size hail three miles from this vantage point (undetermined location). Photo by Pat Kavanaugh.

Christopher C. Burt
Weather Historian

Thunderstorms

Permalink

May 2012 Global Weather Extremes Summary

By: weatherhistorian, 6:19 PM GMT on June 14, 2012

May 2012 Global Weather Extremes Summary

May was notable weather-wise for more spring heat records in the U.S.A. and much of Europe. National heat records (for warmest May temperature on record) occurred in Scotland, Greenland, France, and came close to such in Norway and Spain. Globally it was the 2nd warmest May on record (combined land and ocean) and the warmest May on record for the northern hemisphere. Deadly flash floods struck portions of Nepal, China, Afghanistan and the Amazon River reached its highest level on record at Manaus, Brazil. A late season snowfall shocked the city of Sarajevo, Bosnia.

Below is a summary some of the month’s highlights.

NORTH AMERICA

The warm spring continued into May for the eastern two thirds of the continental U.S. culminating in 2012 recording its warmest spring (March-May) period on record (since at least 1895). However, unlike March and April, few significant monthly heat records were broken although monthly records were tied in Detroit (95°F), Flint (93°), Cleveland (92°F), and Toledo, Ohio (96°). Chicago’s O’Hare Airport and Midway Airport both registered 97° on May 27th, one degree shy of the monthly May record of 98° at O’Hare and well short of the record 102° at Midway, both set on May 31, 1934.

Precipitation-wise there was a sharp divide between the haves and havenots in the middle of the country: Arkansas reported its 2nd driest May on record while Minnesota endured its 2nd wettest such.





The month was relatively calm so far as tornadoes and severe storms are concerned. The tropical storm season got off to an early start with two named storms (Alberto and Beryl) developing off the Southeast coastline with Beryl making landfall in northern Florida. The storms caused little damage and brought welcome rainfall to the drought-plagued region.

An intense (in relative terms) heat wave affected southern Greenland during the last week of the month. An all-time May high temperature for the country was recorded at Narsarsuaq on May 27th when a reading of 24.8°C (76.6°F) was measured. This was almost as warm as the June record for Greenland (25.2°C/77.4°F) also set at Narsarsuaq on June 22, 1957. Jeff Masters wrote a detailed account of this heat event in his of May 31st.

In spite of the warmth at the end of the month, the coldest temperature measured in the Northern Hemisphere during May was -42.7°C (-44.9°F) at Summit station on Greenland on May 12th.

SOUTH AMERICA and CENTRAL AMERICA

The large Amazonian city of Manaus (population 1.7 million) was inundated by its worst flood in 100 years when the Rio Negro overflowed its banks on May 21st. The city lies near the confluence of the Amazon and Rio Negro Rivers whose headwaters recorded much above rainfall for the month prior to the flooding. Some 2,550 people lost their homes to the floods.



The Amazonian city of Manaus experienced its worst flooding in 100 years when the Rio Negro River overflowed its banks in mid to late May. Photo from International Business Times TV.

EUROPE

Western Europe experienced some periods of record-breaking heat. In France the temperature peaked at 35.2°C (95.4°F) at Le Luc on May 12th, the warmest May reading on record for the country outside of Corsica. In Spain it reached 40.7° (105.3°F) at Seville East, close to the all-time European May record of 42.0°C (107.6°F) set at Diga Lentini, Sicily, Italy on May 23, 1994. Norway came very close to its national May record high temperature when 31.1°C (88.0°F) was measured at Gverv on May 24th. This was the earliest 30°C+ reading on record for the country. The all-time May record of 31.8°C (88.3°F) set in 1908 still stands.

Scotland recorded its warmest May temperature on record when it reached 29.3°C (84.7°F) at Achnagart on May 25th. The coldest temperature measured in the U.K. during May was -6.2°C (20.8°F) at Saughall, East Ayrshire, Scotland on May 5th. The greatest 24-hour precipitation amount recorded was 101 mm (3.98") at Kinlochewe on May 13-14.

A rare heavy May snowfall blanketed the city of Sarajevo, Bosnia with up to 10 cm (4”) of snow on May 14th. Thunder accompanied the storm. Amazingly, it was 27.8°C (82.0°F) just 48 hours previous to the advent of the snowstorm! The temperature fell to 0.6°C (33.0°F) during the snow event.

AFRICA

The hottest temperature recorded in the southern hemisphere during May was 37.8°C (101.2°F) at Pongola, South Africa on May 1st. Kaolack, Senegal apparently measured its hottest temperature on record on May 8th with a reading of 47.8°C (118.0°F) although this reading is suspicious (highest hourly METAR reading was ‘just’ 113°.

ASIA

An avalanche off the slopes of Mt. Annapurna in Nepal apparently formed a temporary dam on the Seti Gandaki River near Pokhara that burst causing a flash flood in the valley below. At least 71 drowned including 3 Ukrainian trekkers on May 4th.

Flash floods in northern Afghanistan (triggered by 8 hours of torrential rains on May 6th) killed at least 26 with an additional 100 missing in the provincial capital of Sar-e-Pul.

Mudslides caused by heavy rainfall in Gansu Province, China killed at least 44 during the second week of the month. Over 150,000 were evacuated from affected regions.

An all-time record high temperature of 36.7°C (98.1°F) was recorded on the normally temperate resort island of Ko Samui, Thailand on May 1st. In Bangkok the temperature soared to 40.0°C (104.0°F) on the same day, just 0.8°C (2°F) short of the sweltering city’s all-time record high temperature of 40.8°C (106°F).

The hottest temperature recorded in the northern hemisphere and the world during May was 49.5°C (121.1°F) at Moen Jo Daro and Larkana, Pakistan on May 31st.

AUSTRALIA

Australia was, for the most part, drier than normal during May with warmer than normal temperatures in the west and cooler than normal in the north. A small portion of coastal Western Australia around the town of Carnarvon experienced its warmest May on record.





Maps of the maximum temperature deciles (top) and precipitation deciles (bottom) for Australia during the month of May. Courtesy of the Australian Bureau of Meteorology.

The warmest temperature reported for the month was 37.4°C (99.3°F) at Mardie, Western Australia on May 13th and the coldest reading -10.°C (14.0°F) at Charlotte Pass, New South Wales on May 30th. The greatest calendar day rainfall was 215mm (8.46”) at Halifax on May 25th.

NEW ZEALAND/SOUTH PACIFIC

It was a fairly temperate month for New Zealand extreme weather-wise. The warmest temperature for the month occurred at Whangarei, North Island on May 9th with a 23.4°C (74.1°F) reading and the coolest being -81.°C (17.4°F) at Ranfurly, South Island on May 20th. The greatest calendar day rainfall was 207 mm (8.15”) at North Egmont, North Island on May 27th.

ANTARCTICA

The coldest temperature in the southern hemisphere and the world during May was -81.2°C (-114.2°F) recorded at Vostok on May 26th.

KUDOS Thanks to Maximiliano Herrera for global temperature extremes data, Stephen Burt for the U.K. extremes, and Jeremy Budd for New Zealand weather extremes.

Christopher C. Burt
Weather Historian

Extreme Weather

Updated: 7:52 PM GMT on June 15, 2012

Permalink

Inconsistencies in NCDC Historical Temperature Analysis?

By: weatherhistorian, 6:46 PM GMT on June 06, 2012

Inconsistencies in NCDC Historical Temperature Analysis?

Jeff Masters and I recently received an interesting email from Ken Towe who has been researching the NCDC historical temperature database and came across what appeared to be some startling inconsistencies. Namely that the average state temperature records used in the current trends analysis by the NCDC (National Climate Data Center) do not reflect the actual published records of such as they appeared in the Monthly Weather Reviews and Climatological Data Summaries of years past. Here is why.

An Example of the Inconsistency

Here is a typical example of what Ken uncovered. Below is a copy of the national weather data summary for February 1934. If we look at, say Arizona, for the month we see that the state average temperature for that month was 52.0°F.



The state-by-state climate summary for the U.S. in February 1934. It may be hard to read, but the average temperature for the state of Arizona is listed as 52.0°F From Monthly Weather Review.

However, if we look at the current NCDC temperature analysis (which runs from 1895-present) we see that for Arizona in February 1934 they have a state average of 48.9°F, not the 52.0°F that was originally published:



Here we see a screen capture of the current NCDC long-term temperature analysis for Arizona during Februaries. Note in the bar at the bottom that for 1934 they use a figure of 48.9°.

Ken looked at entire years of data from the 1920s and 1930s for numerous different states and found that this ‘cooling’ of the old data was fairly consistent across the board. In fact he produced some charts showing such. Here is an example for the entire year of 1934 for Arizona:



The chart above shows how many degrees cooler each monthly average temperature for the entire state of Arizona for each month in 1934 was compared to the current NCDC database (i.e. versus what the actual monthly temperatures were in the original Climatological Data Summaries published in 1934 by the USWB (U.S. Weather Bureau). Note, for instance, how February is 3.1°F cooler in the current database compared to the historical record. Table created by Ken Towe.

So Why the Difference in current NCDC records and past USWB records?

The basic reason for the difference is that the NCDC has begun to switch over from using what they call the ‘Traditional Climate Division Data Set’ (TCDD) to a new ‘Gridded Divisional Dataset’ (GrDD) that takes into account inconsistencies in the TCDD. Here is a summary of what was wrong with using the TCDD data sets to determine temperature averages and trends. This is a quote from ‘Transitioning from the traditional divisional dataset to the Global Historical Climatology Network-Daily gridded divisional dataset’ by Chris Fenimore, Derek Arndt, Karin Gleason, and Richard R. Heim Jr., NOAA/NESDIS/NCDC, Asheville, NC:

“The GrDD is designed to address the following general issues inherent in the TCDD:

1. For the TCDD, each divisional value from 1931-present is simply the arithmetic average of the station data within it, a computational practice that results in a bias when a division is spatially under sampled in a month (e.g., because some stations did not report) or is climatologically inhomogeneous in general (e.g., due to large variations in topography).

2. For the TCDD, all divisional values before 1931 stem from state averages published by the U.S. Department of Agriculture (USDA) rather than from actual station observations, producing an artificial discontinuity in both the mean and variance for 1895-1930 (Guttman and Quayle, 1996).

3. In the TCDD, many divisions experienced a systematic change in average station location and elevation during the 20th Century, resulting in spurious historical trends in some regions (Keim et al., 2003; Keim et al., 2005; Allard et al., 2009).

4. Finally, none of the TCDD’s station-based temperature records contain adjustments for historical changes in observation time, station location, or temperature instrumentation, inhomogeneities which further bias temporal trends (Peterson et al., 1998).”


The new GrDD is based upon 25 square kilometer (about 9.6 square miles) gridded divisions rather than the traditional regional climate divisions used in the TCDD. The original raw data of specific weather stations has not been changed, but for the purpose of the GrDD analysis the temperature assigned to a grid that happens to include a specific weather station will not match the actual station measurement since the gridded area may include several different weather stations and will also be weighted to take local topography and urbanization (heat island) issues into account. The complete transformation to the GrDD from the TCDD is slated to be complete in 2013 but has been used to some degree already since about 2007.

The impact on the long-term climate record is summarized here (from the same document cited above):

IMPACTS (PRELIMINARY FINDINGS)

Using the methods mentioned above, we identified the climate divisions, states and regions for which the data are impacted the most by this transition. In the aggregate, the GrDD dataset is slightly cooler and wetter when compared to the TCDD, but significant regional differences are apparent (Fig. 1). Typically, the greatest deviations occur in areas with large elevation differences, divisions which border Canada and Mexico, and divisions lacking a large network of stations early in the record.”

Here are two maps illustrating how the change has affected the long-term means for temperature and precipitation by traditional divisional units in the U.S.:





The report concludes with the following comment:

CONCLUSION

”The GrDD is a modern, quality-assured database that improves upon the historical monthly temperature and precipitation data that are currently available with the TCDD. Use of these data will improve our understanding of observed changes in climate across the contiguous U.S. (CONUS). Regression techniques used to derive pre-1930 divisional data in the TCDD have been replaced by real station data in the GrDD, improving comparisons made to early 20th Century data. Because of the different algorithms used, slight variances in temperature and precipitation averages may be seen throughout the data record. The average change in trend was about 0.06°F per century. The annual temperature trend in each division is between -0.3°F and +0.3°F per century and only three climate divisions had differences in their mean larger than 0.3°F per century. In terms of precipitation, the mean change in slope is slightly negative for the annual period”.

A Short History of U.S. Weather Data Collection

The first collection of weather data statistics published in the U.S. appeared in 1857 when a book titled ‘Climatology of the United States and of the Temperate Latitudes of the North American Continent’ written by Lorin Blodget. The book contains detailed monthly and annual temperature and precipitation statistics for about 200 or so locations in the U.S. collected from a variety of different sources (mostly military and the Smithsonian Institute) going back in some cases to the 1780s (and made by various individuals).



Title page of Blodget’s book that included the first published U.S. climate statistics for the U.S.

In 1874 the Smithsonian Institute relinquished its weather data collection responsibilities and passed them on to the Signal Service of the Army. The U.S. Weather Bureau (USWB) was established in 1890 under the umbrella of the U.S. Dept. of Agriculture in 1890 and assumed most of the weather data collection responsibilities. In 1895 the Weather Bureau instituted a homogenization of data collection (meaning it adopted a uniform plan of observations for all it weather sites across the country). In 1906 the USWB published its first comprehensive volume of U.S. weather data in ‘Bulletin Q: Climatology of the United States’ edited by Alfred Judson Henry. This book contains complete weather statistics for every site in the U.S. that had both temperature and precipitation (about 650 stations in all plus about another 1000 that collected precipitation data only). In 1970 the USWB became the National Weather Service (NWS).

Here is a short timeline summary of the above (note the overlapping of various agencies over time):

1820-1890: Medical Dept. of the Army military posts

1849-1874: Smithsonian Institute cooperating observers

1870-1905 (approx): Signal Service of the U.S. Army

1890-1970: U.S. Weather Bureau, Dept. of Agriculture

1970-present: National Weather Service (NOTE: the NCDC was established in the 1950s and is part of NOAA not the NWS).

There are currently about 5700 COOP, ASOS, and NWS sites that collect both temperature and precipitation data and an additional 5-6000 that collect precipitation data only.

It will be interesting to see how the changes in weather data analysis will affect the temperature and precipitation long-term averages across the contiguous U.S.

KUDOS: Ken Stowe for his diligent research in comparing the historical weather data records.

Christopher C. Burt
Weather Historian

Temperature Climate Change

Updated: 1:54 AM GMT on June 07, 2012

Permalink

About weatherhistorian

Christopher C. Burt is the author of 'Extreme Weather; A Guide and Record Book'. He studied meteorology at the Univ. of Wisconsin-Madison.