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Denver’s September 2013 Climate Summary

Temperature

During the month of September 2013, Denver, CO’s (link updated monthly) temperatures were 2.8°F above normal (66.4°F vs. 63.6°F).  The National Weather Service recorded the maximum temperature of 97°F on the 5th and 6th; they recorded the minimum temperature of 38°F on the 28th.  Here is the Denver temperature September 2013 time series:

 photo Denver_Temps_201309_zps687d6b03.png

Figure 1. Time series of temperature at Denver, CO during September 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

The month started off with a heat wave, as a result of an anomalous high pressure ridge over the western US.  It’s not obvious on this chart, but the week of September 8th ushered in a big change from the early month heat wave, which I discuss in the precipitation section below.

Denver’s temperature was above normal for the past five consecutive months.  May 2013 ended a short streak of four months with below normal temperatures.  Looking back a little further in time, October 2012 broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Through September, 2013, there were 57 90°F+ days in 2013, which means 2013 gained sole 4th place status of most 90°F days in one year.  Last year, the hottest summer on record for Denver, there was an astounding 73 90°F+ days!  Thankfully, this year also featured far fewer 100°F+ days than 2012: 2 instead of 13 (a record number).  After last year’s record hot summer, summer 2013 felt comparatively cool, which just goes to show how truly monumental last year’s records were.

I haven’t determined if the NWS (or anyone else) collects record high minimum temperatures (warm nighttime lows) in a handy table, chart, or time series.  Denver’s 68°F on Sep. 3rd was such a record (previously 67, set in 1947), as was Sep. 4th’s 69°F (previously 64°F, set in 1995 and previous years).  I’m curious how Denver’s nightly lows have changed in the past 100+ years.  If I find or put something together, I’ll include it in a future post.

Precipitation

Instead of amazing temperature records (although 97°F in September is very hot!), September saw precipitation records.  Total precipitation was much greater than normal during September 2013: 5.61″ precipitation fell at Denver during the month instead of the normal 0.92″!  Most of this fell at DIA on the 14th and 12th of the month (2.01″ and 1.11″).  As I wrote about after the event, Denver and other communities with similar rain totals paled in comparison to southern Aurora and Boulder, which received over 18″ of rain in one week, and more for the month!  Given that the normal annual total precipitation for these places is 15″, Denver and other places received over 1/3 of their yearly annual precipitation total in one month – a month that is normally relatively dry.

During the week of the 8th, the confluence of a slow-moving upper-level low, a surface stationary front, and tropical moisture from both the Pacific Ocean and Gulf of Mexico generated record rainfall over the northern Front Range of Colorado, including Denver.  This rainfall led to devastating flooding, from which communities are just beginning to recover.  About the only good news from this natural disaster is it busted the area’s long-term drought.

Interannual Variability

I have written literally hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


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Denver’s August 2013 Climate Summary

Temperature

During the month of August 2013, Denver, CO’s (link updated monthly) temperatures were 2.1°F above normal (74.6°F vs. 72.5°F).  The National Weather Service recorded the maximum temperature of 99°F on the 20th and they recorded the minimum temperature of 52°F on the 9th.  Here is the time series of Denver temperatures in August 2013:

 photo Denver_Temps_201308_zps974cdaa4.png

Figure 1. Time series of temperature at Denver, CO during August 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

The month started off cooler than normal as this year’s very active monsoon continued well into August 2013.  High pressure began to dominate the region again in the middle of the month.  Note the large number of days with daily mean temperatures equal to or greater than 78°F.  This was mainly due to the excessive nighttime heat (note the blue line above the climatological normal lows), but also the daily high temperatures in the mid to upper-90s.

Denver’s temperature was above normal for the past four months in a row.  May 2013 ended a short streak of four months with below normal temperatures.  October 2012 broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Through September 4th, 2013, there were 50 90°F+ days in 2013, which ties three other years (1960, 1964, 2011) for 10th most 90°F days.  As of September 5th, the NWS forecast calls for an additional four days with maximum temperatures equal to or greater than 90°F, which would push the yearly total to 54, good for a tie for sixth place.  Last year, the hottest summer on record for Denver, there was an astounding 73 90°F+ days!  Thankfully, this year also featured far fewer 100°F+ days than 2012: 2 instead of 13 (a record number).

I haven’t determined if the NWS (or anyone else) collects record high minimum temperatures (warm nighttime lows) in a handy table, chart, or time series.  Denver’s 68°F on Sep. 3rd was such a record (previously 67, set in 1947), as was Sep. 4th’s 69°F (previously 64°F, set in 1995 and previous years).  I’m curious how Denver’s nightly lows have changed in the past 100+ years.  If I find or put something together, I’ll include it in a future post..

Precipitation

Precipitation was greater than normal during August 2013: 2.78″ precipitation fell at Denver during the month instead of the normal 1.69″.  Most of this fell at DIA on the 22nd of the month (1.94″).  This wasn’t the case for every location in the Denver metro area however since precipitation is such a variable phenomenon.

Precipitation that fell during the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a mid-August 2013 post.  Almost all of Colorado continues under at least some measure of drought in early September 2013 (the exception being along the Front Range in northern Colorado, which received almost daily monsoon rainfall in August).  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however.  The good news is this area shrank in the last month or so.  Colorado still needs the jet stream to substantially shift position this fall and next spring in order to receive the amount of precipitation required to break the long-term drought.  The last NWS 3-month projection didn’t indicate that this was likely to happen.  Hopefully, for the state’s sake, I hope the NWS is wrong.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


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Denver’s July 2013 Climate Summary

Temperature

During the month of July 2013, Denver, CO’s (link updated monthly) temperatures were 0.1°F above normal (74.3°F vs. 74.2°F).  The National Weather Service recorded the maximum temperature of 100°F on the 11th and they recorded the minimum temperature of 55°F on the 2nd.  Here is the time series of Denver temperatures in July 2013:

 photo Denver_Temps_201307_zps3eecd5f9.png

Figure 1. Time series of temperature at Denver, CO during July 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

Compared to spring 2013, June and July brought less extreme weather to the Denver area.   After a very warm start to the month’s temperature due to high pressure that covered the area since mid-June, cooler temperatures were the rule for the 2nd half of the month.  This change was due to an active monsoon season.  Clouds formed nearly every day and the NWS measured rain 9 out of the last 18 days of the month – a big change from last year.

Denver’s temperature was above normal for the past three months (May- June-July).  May 2013 ended a short streak of four months with below normal temperatures.  Seven of the past twelve months were warmer than normal.  October finally broke last year’s extreme summer heat, which included the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Precipitation

Precipitation was lighter than normal during July 2013: only 1.98″ precipitation fell at Denver during the month instead of the normal 2.16″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received rainfall on days that the official Denver recording site did not, which is the usual case for convective-type precipitation.

Precipitation that fell during the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a mid-August 2013 post.  Almost all of Colorado continues under at least some measure of drought in early September 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however and the area with D4 conditions slowly expanded during the past few months.  Absent a significant shift in the upper-level jet stream’s position, the NWS expects dry conditions to persist over CO during the next one to three months, which will likely worsen drought conditions.


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Denver’s June 2013 Climate Summary

Temperature

During the month of June 2013, Denver, CO’s (link updated monthly) temperatures were 3.7°F above normal (71.1°F vs. 67.4°F).  The National Weather Service recorded the maximum temperature of 100°F on the 11th and they recorded the minimum temperature of 39°F on the 2nd.  Here is the time series of Denver temperatures in June 2013:

 photo Denver_Temps_201306_zpsee96454c.png

Figure 1. Time series of temperature at Denver, CO during June 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

In comparison to April 2013, June 2013 brought less extreme weather to the Denver area.   After a moderate start to the month’s temperature, high pressure began to dominate the area by the 11th through the end of the month.  This high pressure brought warmer than average temperatures, which offset the early month cool snap.  This same pattern brought warmer than average temperatures to much of the southwestern United States, culminating in extremely dangerous heat at the end of the month from Idaho to Arizona.

Denver’s temperature was above normal for the past two months in a row.  May 2013 ended a short streak of four months with below normal temperatures.  Seven of the past twelve months were warmer than normal.  October broke last year’s extreme summer heat including the warmest month in Denver history: July 2012 (a mean of 78.9°F which was 4.7°F warmer than normal!).

Precipitation

Precipitation was lighter than normal during June 2013: only 0.75″ precipitation fell at Denver during the month instead of the normal 1.98″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received rainfall on days that the official Denver recording site did not, which is the usual case for convective-type precipitation.

Precipitation a couple of months ago alleviated some of the worst drought conditions in northern Colorado.  The link goes to a late April 2013 post; further relief occurred in May with regular rain events.  With below average precipitation in June for most areas, drought conditions unfortunately worsened during the month.  All of Colorado continues under at least some measure of drought in early July 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however and the area with D4 conditions slowly expanded during the past few months.  Absent a significant shift in the upper-level jet stream’s position, the NWS expects dry conditions to persist over CO during the next one to three months, which will likely worsen drought conditions.  I will write an updated drought post within the week.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short of duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.  If temperatures continue to track warmer than normal in most months, the next set of normals will clearly demonstrate a continued warming trend.


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Denver’s May 2013 Climate Summary

Temperature

During the month of May 2013, Denver, CO’s (link updated monthly) temperatures were 0.8°F above normal (57.9°F vs. 57.1°F).  The maximum temperature of 88°F was recorded on the 17th while the minimum temperature of 19°F was recorded on the 2nd.  Here is the time series of Denver temperatures in May 2013:

 photo Denver_Temps_201305_zpsacd74199.png

Figure 1. Time series of temperature at Denver, CO during May 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

In comparison to March and April 2013, May 2013 brought much less extreme weather to the Denver area.   After a cold start to the month, there was a general regime change that allowed high pressure to dominate in the middle and at the end of the month.  This high pressure brought warmer than average temperatures, which offset the early month cold snap.

Precipitation

Precipitation was lighter than normal during May 2013: only 0.82″ precipitation fell at Denver during the month instead of the normal 2.12″.  Precipitation is a highly variable quantity though.  The west side of the Denver Metro area received higher than normal precipitation during the same time period.

Precipitation in the past couple of months alleviated some of the worst drought conditions in northern Colorado.  The link goes to a late April 2013 post; further relief occurred in May with regular rain events.  All of Colorado continues under at least some measure of drought in early June 2013.  The worst drought conditions (D4: Exceptional) continue to impact southeast Colorado however.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.


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Denver’s April 2013 Climate Summary With A Bonus

During the month of April 2013, Denver, CO (link updated monthly) recorded a 74°F difference between maximum and minimum temperatures.  This fact tells us nothing about how temperatures compare to climatological norms however.  For the entire month, Denver was 5.7°F below normal (41.7°F vs. 46.4°F).  The maximum temperature of 80°F was recorded on the 29th while the minimum temperature of 6°F was recorded on the 10th.  Here is the time series of Denver temperatures in April 2013:

 photo Denver_Temps_201304_1_zps0b7f12c3.png

Figure 1. Time series of temperature at Denver, CO during April 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

There is a big disparity between 2013 temperatures and normal temperatures, especially daily maxima.  Three outbreaks of Arctic air impacted Denver during the month, which set record low temperatures on four different days.  This graph also shows something else that is eye-opening: five daily maximum temperatures were equal to or lower than the climatological daily minimum temperature!  As someone who was ready for spring to spring, April was a disappointing weather month.

But it also got me to thinking about the difference between spring 2013 and spring 2012.  As many of us remember, temperatures in the US in 2012 were very warm compared to climatological norms.  So how different were temperatures in Denver in February-March-April 2013 versus 2012?  I decided to take a look.  Let’s start with extending the dates in Figure 1 back to the beginning of February 2013:

 photo Denver_Temps_201304_2_zps9764a3a4.png

Figure 2. Time series of temperature at Denver, CO during February-April 2013.  Daily high temperatures are in red, daily low temperatures are in blue, climatological normal (1981-2010) high temperatures are the top dark gray line, and normal low temperatures are the bottom dark gray line. [Source: NWS]

This graphic simply demonstrates the same story that I wrote above as well as in my March and February Denver Climate Summary posts.  February was obviously colder than normal due to extended cold air masses over the area.  March and April were also colder than normal, but this was due to vigorous mid-latitude cyclones that brought Arctic air masses south over the area.  This is evident by the significant dips in both maximum and minimum daily temperatures: there was one in the beginning of March, another in the end of March, and three in April.

With this chart in mind, let’s look at the difference between 2012 and 2013.  First, daily maximum temperatures:

 photo Denver_Temps_201304_3_zps34dbe5f9.png

Figure 3. Time series of maximum temperature at Denver, CO during February-April 2012 and 2013.  2013 temperatures are in brick-red, 2012 temperatures are in red, and climatological normal (1981-2010) high temperatures are the dark gray line with green crosses. [Source: NWS]

My memory of 2012′s maximum temperatures was close to reality.  February 2012 was colder than I remember, but this was likely affected by the warmth of April 2012 and the record-setting daily highs in the summer of 2012.  Figure 3 shows a very large difference between daily maximum temperatures in 2012 and 2013, especially after the 22nd of March.  I didn’t remember the cold snap on April 3, 2012.  This graphic shows, by proxy, the lack of spring synoptic storms in 2012.  Daily maximum temperatures rarely fell below the normal for the date.  Instead, April temperatures were as much as 20°F warmer than normal on some dates, but regularly 10°F warmer than normal.  In contrast, 2013 temperatures were often 25-30°F colder than normal.  The difference between two years’ temperatures is a measure of interannual weather variability.  I have more on that below.

 photo Denver_Temps_201304_4_zps477a8e24.png

Figure 4. Time series of minimum temperature at Denver, CO during February-April 2012 and 2013.  2013 temperatures are in blue, 2012 temperatures are in green, and climatological normal (1981-2010) high temperatures are the dark gray line with brown pluses. [Source: NWS]

Again, February 2012′s temperatures were similar to February 2013′s.  The specific dates of temperature swings obviously varies between the two years.  March 2012 and March 2013 also look similar, up until the 22nd of March (see maximum temperatures above also).  Thereafter, the time series diverge with much colder air in place over Denver four different times through the end of April.  2012 had warmer than normal minimum temperatures through most of April.  The combination of warmer than normal nights and days, combined with a relative lack of precipitation in 2012 set the stage for the record-setting warmth in the summer as well as the rapid decline in drought conditions, which are still largely present now.

Interannual Variability

I have written hundreds of posts on the effects of global warming and the evidence within the temperature signal of climate change effects.  This series of posts takes a very different look at conditions.  Instead of multi-decadal trends, this series looks at highly variable weather effects on a very local scale.  The interannual variability I’ve shown above is a part of natural change.  Climate change influences this natural change – on long time frames.  The climate signal is not apparent in these figures because they are of too short duration.  The climate signal is instead apparent in the “normals” calculation, which NOAA updates every ten years.  The most recent “normal” values cover 1981-2010.  The temperature values of 1981-2000 are warmer than the 1971-2000 values, which are warmer than the 1961-1990 values.  The interannual variability shown in the figures above will become a part of the 1991-2020 through 2011-2040 normals.

Precipitation

Precipitation was above normal again during April 2013, extending this new trend to three months.  During the month, 1.87″ of liquid water equivalent precipitation fell, compared to 1.71″ normally.  The wettest April on record was in 1983 when 4.56″ of precipitation fell.  There were three notable weather events during April: a 6″+ snowstorm on the 9th, a 7″+ snowstorm on the 15th, and a 5″+ snowstorm on the 22nd.  In total, the NWS recorded 20.4″ of snow.

The recent precipitation surplus reduced northeast CO drought severity in the last three m months, but did not break it yet.  Above-average precipitation will have to fall for longer than three months for that to happen.  The NWS expects continued drought conditions across most of Colorado through the next three months.  Additional improvement in eastern Colorado might occur, but NOAA and the CPC expects western Colorado drought  to remain the same or worsen.


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Denver’s March 2013 Climate Summary

During the month of March 2013, Denver, CO (link updated monthly) recorded a 74°F difference between maximum and minimum temperatures.  This fact tells us nothing about how temperatures compare to climatological norms however.  For the entire month, Denver was 2.7°F below normal (37.7°F vs. 40.4°F).  The maximum temperature of 76°F was recorded on the 15th while the minimum temperature of 2°F was recorded on the 25th.

 photo Denver_Temps_201303_zps2e96a01c.png

Figure 1. Time series of temperature at Denver, CO during March 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

Precipitation was above normal again during March 2013, making a two-month trend.  During the month, 1.47″ of liquid water equivalent precipitation fell, compared to 0.92″ normally.  The wettest March on record was in 1983 when 4.56″ of precipitation fell.  There were two notable weather events during March: a 6″+ snowstorm on the 9th and the 23rd.  In total, the NWS recorded 23.5″ of snow, 13.5″ more than the normal of 10.0″ for the month.

While more precipitation fell than normal during the month, the drought impacting the region was still not broken.  Above-average precipitation will have to fall for longer than one month for that to happen.  The NWS expects continued drought conditions across most of Colorado through the next three months.  Some improvement in northeast Colorado might occur.  In contrast to February and March, the NWS projects warmer and drier than normal conditions over Colorado during the next three months.


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Denver’s February 2013 Climate Summary

During the month of February 2013, Denver, CO recorded a 58°F difference between maximum and minimum temperatures (20°F less than January!).  This fact tells us nothing about how temperatures compare to climatological norms however.  For the entire month, Denver was 2.4°F below normal (30.1°F vs. 32.5°F).  The maximum temperature of 63°F was recorded on the 17th while the minimum temperature of 5°F was recorded on the 22nd.

 photo Denver_Temps_201302_zps6d6262b9.png

Figure 1. Time series of temperature at Denver, CO during February 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

Precipitation was finally above normal again during February 2013.  During the month, 0.77″ of liquid water equivalent precipitation fell, compared to 0.37″ normally.  For the first time in my life, rain fell across the Denver metro area in February!  On the 6th, it rained very lightly, just enough to make the streets and plants wet.  To add to the oddity and rarity of the situation, the ground was still wet with liquid on the morning of the 7th – it wasn’t cold enough to freeze the rain overnight. A similar event occurred in late January.  Conditions returned to normal in the second half of the month.  Measurable snow finally fell on the 20th and 21st of the month.  Then a significant winter storm hit the area on the 24th, dropping ~9″ of snow across the metro area.  In total, the NWS recorded 14.1″ of snow, 8.2″ more than the normal of 5.9″ for the month.

While more precipitation fell than normal during the month, the drought impacting the region was not broken.  Above-average precipitation will have to fall for longer than one month for that to happen.


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Denver’s January 2013 Climate Summary

During the month of January 2013, Denver, CO recorded a 78°F difference between maximum and minimum temperatures.  Does that tell you anything about whether it was warmer or colder than normal?  No, it does not.  For the entire month, Denver was 0.4°F below normal (30.3°F vs. 30.7°F).  But the maximum temperature of 66°F was recorded on the 24th while the minimum temperature of -12°F was recorded on the 12th.

 photo Denver_Temps_201301_zps238cbc94.png

Figure 1. Time series of temperature at Denver, CO during January 2013.  Daily high temperatures are in red, daily low temperatures are in blue, daily average temperatures are in green, climatological normal (1981-2010) high temperatures are in light gray, and normal low temperatures are in dark gray. [Source: NWS]

Precipitation was below normal again during January 2013.  0.31″ of liquid water equivalent precipitation fell during the month, compared to 0.41″ normally.  For the first time in my life, rain fell across the Denver metro area in January!  Two days after hitting the high for the month, the National Weather Service recorded 0.01″ of rain on the 26th.  I haven’t read anything regarding historical rain in Denver in January, but I think such an event is very rare indeed.  4.6″ of snow fell, which was 2.4″ below the normal of 7.0″.


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Denver Weather & Climate: July 2008, Take 2

I wrote about Denver’s temperature and precipitation status one week ago. There is more data now that continues the story set forth in that post. The record streak of 90 degree plus days has continued since then, including today’s ( 8/4/08 ) high of 95 degrees. The record: 23 consecutive days. Tomorrow’s high temperature is forecasted to be about 85 degrees, due to an expected cooler air mass to Denver’s north moving into northern Colorado.

In addition to the streak, which was just fun to keep track of and not really indicative of anything terribly substantial, Denver’s precipitation continues to threaten to set its own record. Through the end of July, we have the following information, provided by the Denver/Boulder NWS Forecast Office:

Jan 1 – Jul 31 2002; Jan 1 – Jul 31 2008

5.34 inches 3.28 inches

Difference: 2.06 inches

Normal (Jan 1 – Jul 31) 10.25 inches

What’s significant about 2002? It currently ranks as Denver’s all-time driest year on record, dating back to 1878. So through seven months of 2008, Denver’s official precipitation measurements add up to a mere 3.28″. As you can see, that’s ~3/10ths of the normal value. That’s more significant than the >90F temperature streak. The most recent month where precipitation was more than average was October 2007, which is quite a ways back now. This summer was forecasted to be drier than average in a general sense, which has unfortunately come true. And really, Denver hasn’t had the worst of it.

According to the U.S. Drought Monitor, the eastern half or so of Colorado is experiencing some level of drought. But look at the southeastern portion of the state. Seven counties (Cheyenne, Kiowa, Otero, Bent, Prowers, Las Animas and Baca) are experiencing Severe Drought, parts of four counties (Bent, Prowers, Las Animas and Baca) are experiencing Extreme Drought and the bottom portion of one county (Baca) is experiencing Exceptional Drought.

***

I forgot to mention that Denver hasn’t officially received any rain yet in August either. A trace was recorded on the 3rd, but what little precip did fall didn’t measure up to 0.01″ or more. The NWS only discussed data through the end of July, so I’m not sure how things compare through yesterday. I’ll bring in more information as the NWS records it.

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