Hot or cold: Denver's problematic weather records. (Denver Weather Examiner)
Does a move of 12 miles make a difference in what type of weather is seen in Colorado? Longtime residents know that our weather can vary greatly over short distances and this has many questioning the placement of Denver’s official weather monitoring station.
From 1871 to 1949 Denver’s weather was recorded at the National Weather Service’s office in downtown Denver. In January 1950 a move was made to Stapleton International Airport.
As that facility aged Denver opened Denver International Airport on the plains northeast of Denver in 1995. The weather service followed suit and moved the Mile High City’s official weather station the 12 miles to DIA.
Since that time, many weather watchers have noticed problems – DIA is consistently warmer and drier than the old site at Stapleton. Further, its remote location gives conditions far from where most people in Denver live and thus doesn’t accurately represent what they are experiencing.
Even bigger issues arise when comparing weather data taken today with measurements previously recorded at Stapleton or downtown. The different microclimates of the sites are so different that it becomes much like comparing apples and oranges.
This was recently made evident with the string of 90 degree or warmer days we put together. If you went by the station at DIA, the streak lasted 18 days putting in a three way tie for the second longest streak in Denver history. However, no monitoring station closer to the city was as warm.
Further, while July was certainly a wet month, DIA’s precipitation measurements fell far short of most other locations.
Amid concerns about a warming climate, can we trust the measurements at DIA? How is it possible to compare the weather today with historical weather when there is such a large discrepancy?
We recently tackled this topic on the Denver Weather Examiner and the conclusion is obvious – It simply is impossible to correlate current weather records with Denver’s historical ones. Further, the National Weather Service seems intent on ignoring the issue.
Thornton’s June 2011 weather was a relatively typical one with average temperatures but also with above normal precipitation. The month also signifies the official end of the 2010 to 2011 snow season which was absolutely dismal.
In terms of temperatures Denver saw an average temperature for the month of 68.2 degrees. This was just a bit above the normal of 67.6 degrees. Temperatures ranged from a high of 96 degrees on the 28th and 29th down to a low of 45 degrees on the 10th. DIA recorded seven days with 90 degrees or higher temperatures which is one above normal. No temperature records were set for the month.
Here in Thornton we came quite close to mirroring Denver’s official temperatures. Our average temperature was 68.1 degrees with the highest mercury reading of 96.4 degrees coming on the 29th. The lowest temperature in Thornton came on the 3rd at 45.4 degrees.
Precipitation for the month was above normal as DIA’s rain bucket recorded 2.43 inches. This was 0.87 inch above the normal of 1.56 inch and the second month in a row with above normal precipitation. In all, eight days had measurable precipitation and DIA reported thunderstorms on 10 days which is average.
One precipitation record was set during the month when 1.05 inches of rain was recorded on the 20th. This beat the old record for the date of 0.50 inch set in 1939.
We were quite a bit drier in Thornton as our precipitation for the month fell below the Denver normals. We recorded 1.14 inches for the month with the majority of that, 0.87 inch, falling on the 20th.
Denver’s snow season runs from July 1 to June 30 and with the end of the 2010 to 2011 season the numbers show just how poorly we faired in terms of snowfall. The Mile High City recorded a mere 22.8 inches of the white stuff at DIA. This is a whopping 38.9 inches below the normal of 61.5 inches. The season will go into the record books as the second least snowiest snow season since Denver began keeping records in 1882.
Here in Thornton we did not fare any better than Denver on the snowfall front. Our season wrapped up with a dismal 21.2 inches.
Denver, Colorado June 2011 Climate Summary
CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2011
WEATHER OBSERVED NORMAL DEPART LAST YEAR'S
VALUE DATE(S) VALUE FROM VALUE DATE(S)
NORMAL
................................................................
TEMPERATURE (F)
RECORD
HIGH 104 06/26/1994
LOW 30 06/02/1951
HIGHEST 96 06/29 104 -8 99 06/25
06/28
LOWEST 45 06/10 30 15 47 06/23
06/18
06/14
06/12
AVG. MAXIMUM 83.3 82.1 1.2 84.1
AVG. MINIMUM 53.0 53.0 0.0 53.6
MEAN 68.2 67.6 0.6 68.9
DAYS MAX >= 90 7 6.3 0.7 10
DAYS MAX <= 32 0 0.0 0.0 0
DAYS MIN <= 32 0 0.0 0.0 0
DAYS MIN <= 0 0 0.0 0.0 0
PRECIPITATION (INCHES)
RECORD
MAXIMUM 4.96 1882
MINIMUM T 1890
TOTALS 2.43 1.56 0.87 1.60
DAILY AVG. 0.08 0.05 0.03 0.05
DAYS >= .01 8 8.7 -0.7 5
DAYS >= .10 4 MM MM 3
DAYS >= .50 2 MM MM 2
DAYS >= 1.00 1 MM MM 0
GREATEST
24 HR. TOTAL 1.55 06/19 TO 06/20 1.25 06/11 TO 06/12
SNOWFALL (INCHES)
RECORDS
TOTAL 0.4 1919
TOTALS 0.0 T
DEGREE_DAYS
HEATING TOTAL 26 60 -34 38
SINCE 7/1 5707 6128 -421 6441
COOLING TOTAL 126 136 -10 163
SINCE 1/1 135 161 -26 179
FREEZE DATES
RECORD
EARLIEST 09/08/1962
LATEST 06/08/2007
EARLIEST 10/07
LATEST 05/05
.................................................
WIND (MPH)
AVERAGE WIND SPEED 10.4
RESULTANT WIND SPEED/DIRECTION 3/148
HIGHEST WIND SPEED/DIRECTION 48/190 DATE 06/29
HIGHEST GUST SPEED/DIRECTION 72/200 DATE 06/29
SKY COVER
POSSIBLE SUNSHINE (PERCENT) MM
AVERAGE SKY COVER 0.50
NUMBER OF DAYS FAIR 7
NUMBER OF DAYS PC 21
NUMBER OF DAYS CLOUDY 2
AVERAGE RH (PERCENT) 45
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM 0 MIXED PRECIP 0
HEAVY RAIN 3 RAIN 2
LIGHT RAIN 10 FREEZING RAIN 0
LT FREEZING RAIN 0 HAIL 1
HEAVY SNOW 0 SNOW 0
LIGHT SNOW 0 SLEET 0
FOG 4 FOG W/VIS <= 1/4 MILE 0
HAZE 6
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.
Our normally widely varied weather settles into a somewhat standard pattern during the month of July. The mercury climbs each day in what is our hottest month and thunderstorms become very common during the afternoon and evening hours.
The average monthly high temperature for July is 88 degrees and can oftentimes get much higher than that. In fact, the record high temperature for all but seven days during the month are at or above 100 degrees.
Afternoon thunderstorms occur on average every three days during July. These events can be extreme and are known to bring heavy rains and damaging wind and hail.
May 2011 will go into the books as the 11th coldest and 5th wettest May on record in Denver.
There was little doubt that last month was a wet one and now that May 2011 has come to a close we can see that it certainly was. In fact, it was one of the wettest Mays on record and also one of the coldest.
Up until the last few days of the month it looked like we were going to make the top 10 list for coldest Mays on record. But, thanks to a few near-normal days, our average temperature for the month ended at 53.1 degrees. This fell just short of the number 10 spot on the list of 53.0 degrees recorded in 1950.
Nevertheless the month’s average temperature was 4.1 degrees below the normal of 57.2 degrees. Our warmest temperature of the month of 86 degrees was recorded on both the 7th and the 8th and those were two of only three days with temperatures above 80 degrees.
On the low end the coldest temperature was seen on the 5th when the mercury dropped to 28 degrees. This is also the last time we saw a temperature at or below freezing and will almost certainly be the last for the 2010 – 2011 winter season. Coincidentally, May 5th is the average date of our last freeze so we were right on the mark this year.
Here in Thornton we saw an average temperature of 52.9 degrees. Our warmest temperature was 86.8 degrees and our coldest 29.2 degrees.
May brought an abundance of precipitation eliciting many jokes about Denver having swapped locations with Seattle. In all, 4.79 inches of moisture was recorded at Denver International Airport during the month putting it in the books as the 7th wettest May on record. This was 2.47 inches above the May average of 2.32 inches.
Here in Thornton we recorded nearly an inch of precipitation more than what was recorded at DIA. ThorntonWeather.com saw 5.67 inches fall into our bucket for the month.
On average we record 1.3 inches of snow in May but last month continued the trend we saw all winter of a severe lack of snowfall. Only 1.0 inch of the white stuff was recorded at DIA and most of the metro area saw nothing during the month (including Thornton).
Given that it is highly unlikely June will bring any snow to Denver, the 2010 to 2011 season will wrap up with only 22.8 inches of snow – far below the 61.7 inches average. This will put the season into the history books as the 2nd least snowiest snow season on record. Only the 1888 to 1889 season saw less with 21.3 inches.
Thornton actually fared worse throughout the entire snow season and we are going to wrap it up with a paltry 21.2 inches.
June is historically Denver’s severe weather month and severe thunderstorms, tornadoes and hail are notorious visitors to Denver and across eastern Colorado during the month.
In fact, over 40 percent of the tornadoes that occur in Colorado are observed in June and these are typically the most destructive of the year. Thornton of course knows this fact well as this year we celebrate the 30th anniversary of the infamous Thornton tornado of June 3, 1981.
Severe thunderstorms have also caused major property damage across the Front Range during the month. Just last year hail the size of golf balls caused damage across parts of central and northeastern Thornton.
Not only did Denver and Thornton see warmer than normal temperatures in April, so did the rest of the globe. Click the image for a larger version. (NOAA)
With the effects of La Nina still in full force the globe’s temperatures performed as forecasted during April 2011. According to NOAA the month ranked as the seventh warmest April on record while Denver saw warmer and drier than normal conditions as well.
Denver saw an average temperature during the month of 48.4 degrees – 0.8 degree above normal. Temperatures ranged from a record high of 84 degrees on the 2nd down to a low of 19 on the 4th of the month. Fifteen days saw temperatures dip below the freezing mark which is four more than normal.
Here in Thornton we were slightly cooler with an average of 48.1 degrees for April. Our high ranged from 86.3 degrees down to a low of 20.6 degrees.
The lack of precipitation and snowfall was one of the biggest stories of the month for the Mile High City. A mere 1.07 inch of precipitation was recorded in Denver’s rain bucket which was 0.86 inch below the normal of 1.93 inches.
Snowfall was similarly dismal as only 1.2 inches of snow was recorded at Denver International Airport. This was far below the normal of 9.1 inches for April which is historically our fourth snowiest month. Through April 30, a mere 21.8 inches of snow has been recorded at Denver’s official monitoring site at Denver International Airport – the second worst snow season to date.
Thornton was a bit wetter than Denver as we recorded 1.54 inches of liquid precipitation. In terms of snowfall we received only 1.5 inches, most of which (1.3”) fell on the 3rd of the month.
Overall the globe saw warm temperatures as well. The combined land and ocean temperature average for the month was 57.76° F which was 1.06° above the 20th century average. Taken separately the land surface temperature was 2.02° above normal and sea temperatures were 0.70° above normal.
The Earth experienced the seventh warmest April since record keeping began in 1880, as the climate phenomenon La Niña continued to be a significant factor. April’s annual Arctic sea ice extent was the fifth smallest since record keeping began in 1979, while the Antarctic sea ice extent was the fourth smallest.
The monthly analysis from NOAA’s National Climatic Data Center in Asheville, N.C., is part of the suite of climate services NOAA provides government, business and community leaders so they can make informed decisions.
Global Temperature Highlights – April
The combined global land and ocean average surface temperature for April 2011 was the seventh warmest on record at 57.76 F (14.29 C), which is 1.06 F (0.59 C) above the 20th century average of 56.7 F (13.7 C). The margin of error associated with this temperature is +/- 0.13 F (0.07 C).
Separately, the global land surface temperature was 2.02 F (1.12 C) above the 20th century average of 46.5 F (8.1 C), which was the sixth warmest April on record. The margin of error is +/- 0.20 F (0.11 C). Warmer-than-average conditions occurred across most of the southern United States and northern Mexico, much of central South America, Europe and Siberia. Cooler-than-average regions included most of Alaska, western Canada, the northwestern United States, southwestern Greenland and most of Australia.
The April global ocean surface temperature was 0.70 F (0.39 C) above the 20th century average of 60.9 F (16.0 C), making it the 11th warmest April on record. The margin of error is +/- 0.07 F (0.04 C). The warmth was most pronounced in the eastern Atlantic Ocean, the northwestern Pacific and across the Southern Hemisphere mid-latitudes.
The average temperature was the warmest on record for April across the United Kingdom. Germany reported its second warmest April since records began in 1881.
Global Temperature Highlights – Year-to-date
The combined global land and ocean average surface temperature for the year to date (January – April 2011) was 0.86 F (0.48 C) above the 20th century average of 54.8 F (12.6 C), making it the 14th warmest on record. The margin of error is +/- 0.16 F (0.09 C).
The year-to-date worldwide land surface temperature was 1.33 F (0.74 C) above the 20th century average — the 17th warmest such period on record. The margin of error is +/- 0.36 F (0.20 C). Warmer-than-average conditions were particularly felt across the southern half of Greenland, Siberia, northern Mexico, the southern United States and across Africa. Cooler-than-average regions included central Canada, the northern United States, western Russia, Kazakhstan, Mongolia, extreme southeast Asia and most of Australia.
The global ocean surface temperature for the year-to-date was 0.68 F (0.38 C) above the 20th century average and was the 11th warmest such period on record. The margin of error is +/-0.07 F (0.04 C). The warmth was most pronounced across parts of the most of the western Pacific Ocean, the tropical Atlantic Ocean, the North Atlantic near Greenland and Canada, and the southern mid-latitude oceans.
La Niña conditions continued to weaken in April for the fourth consecutive month, although sea-surface temperatures remained below normal across the central and eastern equatorial Pacific Ocean. According to NOAA’s Climate Prediction Center, La Niña will continue to have global impacts as the event continues to decline, but by late spring neither La Niña nor El Niño conditions are expected to prevail in the region.
Effective May 2, 2011, NOAA updated its monthly mean temperature dataset, which is used to calculate global land surface temperature anomalies and trends. The Global Historical Climate Network-Monthly (GHCN-M) version 3 dataset replaced GHCN-M version 2. Beginning with this month’s Global State of the Climate Report, GHCN-M version 3 is used for National Climatic Data Center climate monitoring products. More information on this transition can be found at:http://www.ncdc.noaa.gov/ghcnm.
Polar Sea Ice and Precipitation Highlights
The average Arctic sea ice extent during April was 5.7 percent below average, ranking as the fifth smallest April since satellite records began in 1979.
The April 2011 Antarctic sea ice extent was 7.7 percent below average and was fourth lowest April extent since records began in 1979.
Northern Hemisphere snow cover extent during April ranked as the 15th smallest on record, while the snow cover extent over North America was the 10th largest and Eurasian snow cover was the fifth smallest April snow cover on record.
Average rainfall across Australia was 18 percent above average during April. However, for the first month since June 2010, below-average rainfall was reported in the states of Queensland, South Australia and New South Wales. This broke a streak of nine consecutive months with above-normal rainfall in those states.
Denver's snow season thus far is the second worst in the past 122 years. Click the image for a larger view. (Denver Weather Examiner)
Conditions have been tinder dry across the Colorado Front Range in recent months and certainly one of the biggest factors has been the lack of snowfall. Denver is in fact seeing its second least snowiest snow season on record likely setting the stage for a dangerous fire season ahead.
Through April 30, a mere 21.8 inches of snow has been recorded at Denver’s official monitoring site at Denver International Airport. This is an astonishing 38.6 inches below normal to this point in the season. At the end of March the season ranked as the third worst but after receiving only 1.2 inches of snow in April, the situation looks even more dismal.
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Here in Thornton we have fared slightly poorer. ThorntonWeather.com has recorded 21.2 inches, by far the lowest we have seen at this point in the season since we came into operation nearly five years ago.
Only one other season has seen lower snow totals through the end of April. That occurred 122 years ago during the 1888 to 1889 season when 21.3 inches was recorded. That also ended up being that season’s final total as only a trace was recorded for the rest of the season.
While the plains of Colorado have seen little snow, that hasn’t been the case in the high country. The Colorado Rocky Mountains have been inundated with six of the eight basins reporting from 112 to 165 percent of normal snow water equivalent.
Severe drought conditions have settled in on the eastern half of Colorado with the far southeastern corner of the state event reaching extreme drought levels. NOAA’s drought outlook for the period through July predicts that the drought will continue or intensify.
This situation is cause for alarm for anyone on the plains or in the Colorado mountains east of the Continental Divide. There have already been several significant fires in the foothills and on the far eastern plains. Without some significant precipitation, Colorado may find itself seeing a very dangerous and damaging fire season ahead.
Colorado natives and those that have lived here long enough know that Denver and Colorado weather changes considerably throughout the year. The month of May almost seems to pack four seasons of weather conditions into 31 days. You name it, it can happen.
This being the latter half of spring, May does mean warm temperatures. Temperatures in the 80’s are common and reaching into the 90’s is not unheard of. The normal highs start out at 65 on the first but by the end of the month that climbs to 76. The record high for the month was recorded on May 26, 1942 of 95 degrees.
Denver easily broke the record high temperature for April 2nd.
We knew Saturday was going to be a warm one that would likely break the high temperature record for April 2nd but it far exceeded the forecast.
The record high temperature for today’s date was 76 degrees, last set in 1996. At 1:22pm today the temperature at Denver International Airport hit 84 degrees thus easily eclipsing the old record. Warm winds and plenty of sun helped the Mile High City reach the mark.
Thornton fared even warmer as we hit a high temperature of 86.4 degrees at 3:14pm. Some cloud cover has moved in as of this writing and the temperature has dropped a bit so that may be tops for the day.
Highlighting the contrasting conditions that Denver weather can exhibit at any time, we will follow the record setting warmth today with a blast of winter-like conditions arriving tomorrow. We are expecting a quick shot of snow that will bring some much needed precipitation to the Denver metro area.
Denver is having a pitiful snow season - the third worst in the city's history. (Denver Weather Examiner)
March 31 was the last day of what is historically Denver’s snowiest month but like every other month this season, it fell dismally short in terms of the amount of snowfall. In fact, as it stands now, the Mile High City and Thornton area experiencing their third worst season of snow since record keeping began.
In a normal snow season, through the end of March, Denver historically averages 51.3 inches of snow – a healthy total needed for water supplies, irrigation and to help keep the wildfire danger down.
For the 2010 to 2011 season we are far behind that mark. As of yesterday Denver has recorded a paltry 20.6 inches of snow this season at DIA; a total more than 30 inches below normal. Only two other seasons have seen lower snow totals at this point in the season since record keeping began in 1882 – and those were more than 125 years ago.
For the season Thornton has fared worse than the official Denver totals as we have recorded a mere 19.7 inches (click here for the latest totals). Stapleton has recorded 22.8 and Denver City Park has fared the best with 26.8.
Only one month in this snow season has Denver seen at or above normal snowfall. That occurred in January when we recorded 8.0 inches of snow versus the average for the month of 7.7 inches.
By comparison, the Mile High City’s two snowiest months – March and November respectively – saw very little snowfall. In March a mere 2.5 inches fell in contrast to 11.7 inches on average. November 2010 saw only 1.5 inches of snow versus the November average of 10.7 inches.
The long range climate forecasts from the National Weather Service predict continued drier and warmer than normal weather for the month. April is however historically our third snowiest month so there may be hope, especially given the history of the two seasons on record that were worse than this one.
During the 1883 to 1884 season, April brought 18 inches of snow and the 1884 to 1885 season saw an astounding 32 inches of snowfall in the month. While both snow seasons finished below average, they made up a lot of ground in 30 days.
We can only hope that this season follows suit or we will be in for a very dry – and dangerous – summer.
Thornton’s June 2011 weather was a relatively typical one with average temperatures but also with above normal precipitation. The month also signifies the official end of the 2010 to 2011 snow season which was absolutely dismal.
June is historically Denver’s severe weather month and severe thunderstorms, tornadoes and hail are notorious visitors to Denver and across eastern Colorado during the month.
