Category Archives: Climatology

Climatology, Thornton Weather

Denver records its wettest 4th of July ever; Record draws attention to climate data problems

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According to the National Weather Service, record-setting rain fell in Denver on the 4th of July. But is it accurate to say that? (ThorntonWeather.com)
According to the National Weather Service, record-setting rain fell in Denver on the 4th of July. But is it accurate to say that? (ThorntonWeather.com)

Heavy rain showers put a damper on a lot of Independence Day celebrations yesterday.  Thunderstorms moved across the Front Range dumping rain and hail across northeastern Colorado with enough rain falling to set a record for the 4th of July.

At Denver International Airport (DIA), 1.84 inches of rain was recorded.  This easily eclipses the old 4th of July record dating back to 1909 when 1.44 inches fell. 

Here in Thornton we weren’t nearly as wet having recorded 0.81 inches for the storms that moved through.  Some of the other rainfall totals from across the metro area:

  • Arvada: 0.89 inch
  • Aurora: 0.86 inch
  • Broomfield: 0.57 inch
  • Castle Rock: 0.71 inch
  • Conifer: 0.31 inch
  • Centennial:  1.01 inches
  • Denver (north): 0.51 inch
  • Littleton: 0.26 inch
  • Longmont: 0.43 inch

Denver, we have a problem

The rain totals at DIA were impressive however comparing them to the other amounts recorded at stations across the metro area once again highlights problems with Denver’s climate records.  As we have discussed before on Examiner.com, moving Denver’s official monitoring station to DIA is forever altering climate records. 

The rain yesterday was heavy in places but nowhere in the central Denver area measured anywhere near the amount DIA recorded (see map below).   When the National Weather Service (NWS) announces a “record” like the rain yesterday, it is comparing the measurements at DIA to historical records taken at the old Stapleton International Airport from 1950 to 1995 and downtown from 1871 to 1949. 

Is it accurate to claim a weather record when the station doing the recording is 12 miles away from where historical records were made?  Of course not and this is a problem.   

Last year the NWS partially conceded to the problem and installed an official monitoring station in Denver City Park.  Denver’s official records however still come from the station at DIA. 

The National Weather Service either needs to start recording Denver’s official statistics from the new station or it needs to quit comparing data from DIA to that recorded before the move in 1995. 

Denver’s climate records are forever being altered and the public is being misled. 

The National Weather Service recorded 1.84 inches of rain at the official monitoring station at DIA on Sunday, July 4, 2010. No other station in the area recorded near this amount though. (MesoWest / ThorntonWeather.com)

Climatology, Thornton Weather

Thornton’s June weather preview – Severe weather arrives in Colorado

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June typically brings severe weather to Thornton and the Denver area.
June typically brings severe weather to Thornton and the Denver area.

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.  Severe thunderstorms have also caused major property damage across the Front Range during the month.

In just the last 25 years or so, there have been some particularly notable storms in June.  Tornadoes have struck the metro area including one that longtime Thornton residents will recall on June 3, 1981.  53 residents were injured, 25 homes were destroyed and 239 other structures were damaged.  Others tornadoes in the metro area include southeast Denver and Aurora on June 8, 1986 and east Denver on June 13, 1984.  Severe thunderstorms occurring on June 13, 1984 dumped large hail making it one of the worst and the second costliest storm in Denver history.  More recently, on June 20, 2001, a major hail storm moved across Denver International Airport dropping hailstones as big as two inches in diameter. Damage was extensive on and near the airport.

Read more about Thornton and Denver’s June weather including a look back at last year’s stormy June and a look ahead at this year.

Climatology

April 2010 goes down in books as the hottest globally

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Combined global temperature anomalies for April 2010. (NOAA)According to data released by the National Oceanic and Atmospheric Administration (NOAA), the combined land and sea temperatures for last month were the warmest April temperatures on record. Individually, sea surface temperatures were the warmest for any April and surface temperatures were the third warmest.

Utilizing data from the National Climatic Data Center (NCDC), the agency reported that the combined temperature of 58.1°F (14.5°C) was 1.37°F (0.76°C) above the 20th century average of 56.7°F (13.7°C).
For the period from January to April, temperatures also were the warmest first quarter on record. NOAA said the combined temperature over the period was 56.0°F (13.3°C). That is 1.24°F (0.69°C) above the 20th century average.

Arctic sea ice, long considered a harbinger of global warming, was reported at 2.1 percent below average. NOAA conceded however that sea ice was at its highest April extent since 2001. As reported previously, Arctic sea ice has seen three consecutive years of increasing measurements.

In the United States, NOAA said that April featured above normal temperatures and below normal precipitation. Much of the eastern half of the nation experienced warmer than normal temperatures resulting in measurements 2.3°F above average and going down in the books as the 14th warmest April on record.

For more on the climate, global warming and manmade climate change be sure to visit the Climate Change Examiner. 

Climatology

May’s weather preview – Four seasons in one month

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Thornton's May weather previewColorado 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.

The temperatures aren’t always mild in May and the weather conditions can certainly get wild.  Get all the details in our complete May weather preview.

Climatology, Thornton Weather

Denver’s March was warmer, drier than average

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Denver's March 2010 snowstorm
Despite the snowstorm that struck on March 23rd and 24th and the rain that fell beforehand, the National Weather Service says Denver's March precipitation was below normal.

According to the Denver / Boulder office of the National Weather Service, Denver’s March weather was warmer and drier than normal. The latest climate summary from the service would seem to contradict what Denver residents actually experienced, at least in terms of precipitation.

The report starts with a seemingly contradictory statement saying, “Denver’s March 2010 finished with below normal liquid moisture in spite of finishing above normal in the snowfall category.”

According to the report, Denver recorded 0.80 inch of precipitation, well below the normal of 1.28 inches. Most of that occurred in conjunction with the snowstorm on the 23rd of the month when the official measuring station at Denver International Airport (DIA) reported 0.61 inch of precipitation.  By contrast, ThorntonWeather.com recorded 1.42 inches of precipitation from that storm alone and 1.90 inches for the month. 

March is Denver’s snowiest month recording on average 11.7 inches of snow. This year the month yielded 12.8 inches, most of which fell during the snowstorm that struck from the 23rd to the 24th. The service noted that this was the third month this snow season with above normal snowfall.  We recorded more snow here in Thornton with 15.3 inches. 

Overall for the season, Denver has recorded 58.8 inches of snow which is 7.5 inches above the average snowfall up to this point. Denver’s snow season runs from July through June and we average 61.7 inches over that period so for 2010 we are quickly approaching a ‘normal’ year.

The average temperature as recorded at DIA was 41.0 degrees which was 1.4 degrees above the normal of 39.6 degrees. Temperatures for the month ranged from a high of 82 degrees on the 30th down to a low of 13 degrees on the 20th. The 82 degree high temperature on the 30th broke the record for that date of 81 degrees set way back in 1879.

Controversy once again surrounds measurements in latest report

Questions have been raised numerous times about how the move of Denver’s official monitoring station to DIA has skewed the climate records for the city. Evidence shows that the 14 mile move has forever altered Denver’s records.

The March 2010 climate summary once again highlights the problem. Comparison of temperature records for DIA versus areas closer to historical monitoring locations continue to show discrepancies. Standing out even more are precipitation records that are curious at best, ridiculous at worst given the wet snowstorm that struck on the 23rd and 24th.

The Denver Weather Examiner is in the process of updating our previous investigation and will have an updated report soon. In the meantime, you may wish to look at the results of the investigation we conducted last year.

Climatology

April weather in Denver – A bit of everything for everyone

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Denver's April weather previewApril marks a transition between winter and summer for most of the country but for Denver it is especially true as we can see a stunning variety of weather. The proverbial April showers are certainly a possibility for Denver. Snow? Tornadoes? Thunderstorms? You bet – all can happen! For good measure throw in a chance for hail and even dust storms and April gives every type of weather condition you could like – or hate.

The good news is that sunshine and warmer temperatures are usually in abundance as the normal highs during the month move up from 57 degrees on the first to 65 degrees on the 30th. It is not unusual to have a number of days well into the 70’s and the low 80’s. We also see the normal lows move above freezing from 30 degrees at the start of the month to 39 degrees by the end. Temperature extremes can hit both ends of the spectrum with a record low of 2 degrees below zero on April 2, 1975 and a record high of 90 degrees on April 30, 1992.

Get the complete details on Denver’s April weather here in our April weather preview.

Climatology

A Preview of Denver’s March Weather – Lots of Changes

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March in Denver typically means frequent and rapid weather changes. The days grow longer and we start enjoying more sunshine and sometimes summer-like weather. However, on occasion arctic air masses can still force their way south into Colorado dropping temperatures quickly and markedly.

These changes are due to March’s “in between” status – elements during the month have much in common with winter and spring. In addition to arctic fronts, Pacific storms frequently move across Colorado from the west and warm moist air streams up from the Gulf of Mexico northeastward into the state. When these cold fronts collide with the warmer air masses the result can be some crazy weather.

For a complete look at what we have experienced in March historically and what we can expect in March 2010, please check out our complete March weather preview. 

Climatology, Thornton Weather

A preview of Denver & Thornton’s February weather

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February comes and serves as a bit of a month of transition between winter and spring. Average temperatures start to climb and things are generally pretty quiet.

However, it is still winter and below freezing temperatures at night still remain the norm. February is not typically a snowy month – in fact only the 6th snowiest – with an average of 6.3 inches. In terms of severe weather, the month joins September and October as being the quietest for Denver.

As we say though, it is a month of transition and as such extremes can and have occurred in the past. From severe cold and snow to beautiful spring-like days we can see it all. Oftentimes the month can lull us into a false sense of spring when the snowiest month – March – has yet to come.

Get all the details complete with historical extremes, statistics, and more in our complete preview here.

Climatology, National Weather, Natural Disasters

Deadly cold envelops Northern Hemisphere from U.S. to China

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Severe cold weather has enveloped the northern half of the globe from the United States to Britain to China. Across the continents, many places are reporting record setting temperatures and lives have been lost due to the Arctic chill.

The eastern half of the United States saw cold, Arctic air pulled down from the north plunging temperatures below freezing in normally mild places as far south as Florida. The widespread cold gripped most of the nation east of the Rocky Mountains to the Gulf of Mexico and the Atlantic Seaboard.

Across the Midwest, temperatures plunged to well below freezing as parts of Iowa recorded temperatures as low as -15 degrees. Jeff Johnson, National Weather Service meteorologist, told the Des Moines Register, “”We’re a solid 30 degrees below normal.” Minneapolis, Minnesota and Chicago, Illinois were seeing wind chills below 0 degrees Tuesday morning.

In Miami, residents accustomed to short sleeve shirts and shorts bundled up as temperatures dropped to freezing. Further north in the state, Orlando saw a low temperature of 21 degrees.

The National Weather Service issued hard freeze warnings across parts of Mississippi, Alabama, Georgia and Florida as the cold threatened the agriculture industry in those states. Freeze watches in Tennessee highlighted the severe cold and came on the heels of reports that four people have died in that state from the cold.

There's more to this story on Examiner.com!The United States is not alone as the cold has turned deadly across the globe.  Get all the details and see some amazing photos at the Natural Disasters Examiner.

Climatology, Thornton Weather

December 2009 goes into the books as seventh coldest on record

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For the second time in the past three months, Denver has experienced monthly average temperatures in the ‘top 10 coldest’ category. In October, the Mile High City saw its second coldest October on record since record keeping began in 1882. Now Denver has just wrapped up its seventh coldest December in history.

Denver’s average December 2009 temperature was 24.1 degrees – a chilly 6.2 degrees below the normal average of 30.3 degrees. That puts the month into the books as the seventh coldest December on record (image right).  Thornton was just a touch colder having recorded an average temperature of 23.8 degrees.

Temperatures during the month ranged from a high temperature of 59 degrees on the 1st down to a low of -17 on the 9th. Overall, the majority of days during the month saw below normal temperatures.

In terms of snowfall, the month did finish above average but not in record setting territory. The National Weather Service recorded 11.1 inches of snowfall at the official monitoring station at Denver International Airport. This was 2.4 inches above the average of 8.7 inches for December.  In Thornton, we received a bit more snow than DIA.  15.3 inches was recorded at ThorntonWeather.com of which the single biggest even was the pre-Christmas storm which dumped 7.5 inches.

 The snow we did receive however was rather dry and as such we finished the month below normal for precipitation. DIA recorded 0.45 inch of precipitation which is 0.18 inch below normal.  Here again, because of the additional snowfall, Thornton fared a bit better with 0.5 inch of precipitation. 

CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO                                 
510 PM MST SAT JAN 2 2010

................................... 

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF DECEMBER 2009...

CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2009

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR'S         
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)      
                                          NORMAL                      
................................................................
TEMPERATURE (F)
RECORD
 HIGH              79   12/05/1939                                    
 LOW              -25   12/22/1990                                    
                        12/24/1876                                    
HIGHEST            59   12/21        79     -20       69  12/02       
                        12/01                                         
LOWEST            -17   12/09       -25       8      -19  12/15       
AVG. MAXIMUM     36.4              44.1    -7.7     41.0              
AVG. MINIMUM     11.9              16.4    -4.5     12.3              
MEAN             24.1              30.3    -6.2     26.6              
DAYS MAX >= 90      0               0.0     0.0        0              
DAYS MAX <= 32     15               5.3     9.7       10              
DAYS MIN <= 32     31              29.2     1.8       30              
DAYS MIN <= 0       6               2.8     3.2        6              

PRECIPITATION (INCHES)
RECORD
 MAXIMUM         5.21   1913                                          
 MINIMUM         0.00   1881                                          
TOTALS           0.45              0.63   -0.18     0.24              
DAILY AVG.       0.01              0.02   -0.01     0.01              
DAYS >= .01         7               5.3     1.7        6              
DAYS >= .10         2                MM      MM        0              
DAYS >= .50         0                MM      MM        0              
DAYS >= 1.00        0                MM      MM        0              
GREATEST
 24 HR. TOTAL    0.20   12/22 TO 12/23        0.10  12/13 TO 12/14       

SNOWFALL (INCHES)
RECORDS
 TOTAL           57.4   1913  SNOWIEST DENVER MONTH SINCE 1881
TOTALS           11.1                8.7              7.1             

DEGREE_DAYS
HEATING TOTAL    1260              1078     182     1179              
 SINCE 7/1       2739              2486     253     2367              
COOLING TOTAL       0                 0       0        0              
 SINCE 1/1        533               696    -163      825              

FREEZE DATES
RECORD
 EARLIEST     09/08/1962                                              
 LATEST       06/08/2007                                              
EARLIEST                        10/07                                 
LATEST                          05/05                                 
.................................................................

WIND (MPH)
AVERAGE WIND SPEED              8.8
RESULTANT WIND SPEED/DIRECTION   3/217
HIGHEST WIND SPEED/DIRECTION    43/220    DATE  12/13
HIGHEST GUST SPEED/DIRECTION    49/220    DATE  12/13

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM *SUNSHINE DATA N/A EFFECTIVE 10/1

NUMBER OF DAYS FAIR            4
NUMBER OF DAYS PC             21
NUMBER OF DAYS CLOUDY          6

AVERAGE RH (PERCENT)     61

WEATHER CONDITIONS. NUMBER OF DAYS WITH 
THUNDERSTORM              0     MIXED PRECIP               0
HEAVY RAIN                0     RAIN                       0
LIGHT RAIN                0     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       2
LIGHT SNOW               10     SLEET                      0
FOG                      11     FOG W/VIS <= 1/4 MILE      1
HAZE                      7                                           
                                                                    
-  INDICATES NEGATIVE NUMBERS.                                      
R  INDICATES RECORD WAS SET OR TIED.                                
MM INDICATES DATA IS MISSING.                                       
T  INDICATES TRACE AMOUNT.