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Mountain West Discussion


Chinook

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We got 0.32" at Fort Collins-CSU. That's the rainiest single day near here since July 8th-9th. I had a thunderstorm in the afternoon, and then one at 9:15PM. I saw lots of nighttime lightning flashes to my south--the storm core was near Loveland. That was fun.

 

As of now, my place has had 0.79" since July 8th-9th. There was 0.49" between July 8th-9th and yesterday, and 0.30" yesterday.  That's kind of a failure of the monsoon. The grass has been getting dry. We have had many days around 90 degrees with plenty of sunshine, and there have been very few days with more than 0.05" of rain.

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I got about 0.33" of rain with low 50's temps here Tues night. We got down to 45 on Wednesday morning. Yesterday and today, there was noticeable haze and sometimes a faint smell of smoke from the distant wildfires. I don't like it. I think my eyes and nose are getting irritated. Today we had 94 with downslope winds, and dew points dipped way down to 27 in the afternoon. 45F up to 94F equals a 49 degree temperature change in 2.5 days.

 

The GFS predicts we will have a persistent upper level ridge coming up in a couple of days.

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  • 2 weeks later...

 

Similar thing here in the Denver metro area and north. No 100 degree days, but things for the most part have gotten hotter and drier since mid July.

 

Let's split the summer months up into 15 or 16 day segments and test out this idea.

 

Denver International:

 

June 1-15: 3 days that were 4+ above average, no days of 94+,  2.24" of rain

June 16-30: 6 days that were 4+ above average, 1 day of 94+, 0.29" of rain

 

July 1-15: 2 days that were 4+ above average, 2 days of 94+, 0.66" of rain

July 16-31: 2 days that were 4+ above average, 3 days of 94+, 0.38" of rain

 

August 1-15:  8 days that were 4+ above average, 7 days of 94+, 0.80" of rain

August 16-31: 6 days that were 4+ above average, 3 days of 94+, 0.27" of rain

 

A large amount of Denver's hot days happened in the August 1-15 time period. The rain between mid-July and August 31st has been below average for the northern Front Range area. Denver had a rainy June, with 2.53" of rain.

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Let's split the summer months up into 15 or 16 day segments and test out this idea.

 

Denver International:

 

June 1-15: 3 days that were 4+ above average, no days of 94+,  2.24" of rain

June 16-30: 6 days that were 4+ above average, 1 day of 94+, 0.29" of rain

 

July 1-15: 2 days that were 4+ above average, 2 days of 94+, 0.66" of rain

July 16-31: 2 days that were 4+ above average, 3 days of 94+, 0.38" of rain

 

August 1-15:  8 days that were 4+ above average, 7 days of 94+, 0.80" of rain

August 16-31: 6 days that were 4+ above average, 3 days of 94+, 0.27" of rain

 

A large amount of Denver's hot days happened in the August 1-15 time period. The rain between mid-July and August 31st has been below average for the northern Front Range area. Denver had a rainy June, with 2.53" of rain.

And of the Aug 1-15 rain. 0.68" came on one day, 8/11. So pretty dry, for summer. It's maybe a little surprising we didn't have more 94+ days with that amount of dryness. August was more than a degree hotter than July on average, too. Here's to perhaps- just maybe- our last hot day, today. Looking forward to having the windows open more.

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Los Angeles/west coast baking in the heat. It has been more than 10 degrees above average for lots of the population of the West.

 

...THE DOWNTOWN LOS ANGELES (USC) CA CLIMATE SUMMARY FOR SEPTEMBER 9 2015...CLIMATE NORMAL PERIOD 1981 TO 2010CLIMATE RECORD PERIOD 1877 TO 2015WEATHER ITEM   OBSERVED TIME   RECORD YEAR NORMAL DEPARTURE LAST                VALUE   (LST)  VALUE       VALUE  FROM      YEAR                                                  NORMAL..................................................................TEMPERATURE (F) YESTERDAY  MAXIMUM        101   1019 AM 102    1956  84     17       91  MINIMUM         76    316 AM  48    1884  64     12       68  AVERAGE         89                        74     15       80
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DEN is at 4.2F warmer than normal for this month (Sep 1st to 13th). 12 out of 13 days have been warmer than normal.  The other day was exactly normal, so no days have been cooler than normal. I really wish it would cool down. The GFS predicts a solidly cooler than normal day around here for 9/23 ---- that's 228 hours in the future!!!

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How predictable or variable is weather in the US?  These two very interesting articles have somewhat different conclusions, depending on how they treat precipitation variability

 

http://fivethirtyeight.com/features/which-city-has-the-most-unpredictable-weather/

 

http://us-climate.blogspot.com/2014/12/intra-annual-climate-variability.html

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New to the Boulder area from the east coast.  I know each year is different but was wondering if there is any information as what to expect in a strong el-nino year in the foothills area

Since we are at about 40 degrees north, the winter temperature impacts from El Nino and La Nina seem to be about zero, on average. In any given month temperature impacts may be very different than zero. Take a look at temperature impacts and precipitation impacts on these two web sites:

 

http://www.esrl.noaa.gov/psd/enso/compare/

 

http://climatecenter.fsu.edu/topics/climate-variability#animations

 

The 2nd web site clearly shows a bias to above average precipitation through much of the winter months for eastern Colorado, and a small-to-moderate bias for below average precipitation for northwest Colorado.

 

Some of the greatest Denver snowstorms have occurred with strong El Ninos. Blizzard of Christmas '82. Blizzard of October '97. Note '02-'03 was an El Nino, but it wasn't as strong as the other two super-El Ninos. In '02-'03, our area had an upper level ridge and very little snow for a long time. Then the Front Range cities got blitzed with 20-35" of snow on March 17 2003.  If a big March storm affects us in 2016, watch out!

 

Big snowstorms here have also occurred in some neutral and La Nina years. Example: In February 2012, Denver got about 16" of snow from a big storm. 2011-12 was a [edit: weak or moderate La Nina] winter, during which the Midwest folks were getting relatively little snow.

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Since we are at about 40 degrees north, the winter temperature impacts from El Nino and La Nina seem to be about zero, on average. In any given month temperature impacts may be very different than zero. Take a look at temperature impacts and precipitation impacts on these two web sites:

 

http://www.esrl.noaa.gov/psd/enso/compare/

 

http://climatecenter.fsu.edu/topics/climate-variability#animations

 

The 2nd web site clearly shows a bias to above average precipitation through much of the winter months for eastern Colorado, and a small-to-moderate bias for below average precipitation for northwest Colorado.

 

Some of the greatest Denver snowstorms have occurred with strong El Ninos. Blizzard of Christmas '82. Blizzard of October '97. Note '02-'03 was an El Nino, but it wasn't as strong as the other two super-El Ninos. In '02-'03, our area had an upper level ridge and very little snow for a long time. Then the Front Range cities got blitzed with 20-35" of snow on March 17 2003.  If a big March storm affects us in 2016, watch out!

 

Big snowstorms here have also occurred in some neutral and La Nina years. Example: In February 2012, Denver got about 16" of snow from a big storm. 2011-12 was a neutral winter, during which the Midwest folks were getting relatively little snow.

really appreciate the information! Looking forward to winter. 

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Who posts the most often about daily weather from each subforum? (other than me.)  I have made a rough map, highlighting the different subforums on AmWx. It seems that of all the subforums that span at least 1 state, (i.e. not NYC nor Philadelphia,) the majority of posts come from the east side of that subforum. The exceptions would be GL/OV (Chicago is in the middle), Tenn Valley (people in Nashville?) and Upstate NY/PA (these people never post anything.)

 

who_posts_most_amwx.png

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Graphics and other information that is totally free on the Weatherbell models page:

 

everything listed as "free" including NWS NDFD snowfall

HRRR 3km

RTMA

2014-2015 climate atlas (it's just an archive of GFS maps)

Global tropical cyclone ACE

Global temperature anomaly

NSSL WRF 4km

WRF 4km (NMM/ARW)

FIM9 Full resolution

WPC precip forecasts

Tropical cyclone heat potential

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Maybe I should post this as well. The CFSv2 predicted monthly precip anomaly for September (based off Aug 22-31 initial conditions). The second plot is percent of normal precip (September 1st-18th). Note: eastern Colorado is on track to get 10%-25% of average precipitation this month.

 

CFSv2_precip_Sep2015_forecast_Aug22_31.g

MonthPNormUS_sep1_to_18.png

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Hot Wednesdays. How long has it been since the Denver area saw a Wednesday that was below normal?

 

Sep 23: Sunny, with a high near 83. A low of 56 occurred this morning. It could be above average by several degrees.
Sep 16: +9deg
Sep 9: +6deg
Sep 2: +9deg
Aug 26: +8deg
Aug 19: -13deg
Aug 12: +2deg
Aug 5: +4 deg (note: 96 scorching degrees)
Jul 29: -5 deg
 

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Temp departures and 500mb anomalies for this month to date. 500mb anomalies have not centered on Colorado, but yet we may be shooting for the warmest September ever in Denver (or other cities near here). Note the two temp anomaly images I posted show nearly the same thing, but with slightly different color schemes.

 

8I12gP0.gif

 

 

mB5y2pW.png

 

 

dg7Iq1J.png

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So... we did it. Long as the DEN temp does not drop more than 15 degrees in the next 3.5 hours, the mean temp for Sept will be 69.4, 1.1 degrees warmer than the existing record high average Sept temp of 68.3. The top 5 are all within 0.6 degrees of 68.3, so this is a big deal. And June's average was only 69.5!

Will it stand for a while? We'll see. Ready for some cooler weather!

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You are right. The average temps were not only record-breaking, they were really record-breaking at 6.0 degrees above average. A 6.0 degrees F anomaly, or greater, positive or negative, is a very rare anomaly for one month. September was nearly as warm as the climate-average for August (72.5) The monthly precipitation at Denver was a measly 0.11". In other parts of the country, they would call that a horrendous drought.

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