The Weather Wire

 

September 2009                                                                                                            Volume 17 Number 09

 

Contents

 

 

 
·   Winter Outlook
 

·   Drought Monitor

 

·   August

    Summary

 

·   August Stats

 

·   September Preview

 

·   Sunrise/Sunset

 

·   Rain Totals

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August

Avg High -85.6

Avg Low - 55.1

Snow - 0.0"

Season Snow - 38.1"

Precipitation - 1.14"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

September

Avg High - 77.4

Avg Low - 47.3

Avg Snow -  2.1"

Avg Precip - 1.14"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Skyview Weather 

2350 N Rocky View Rd

Castle Rock, CO 80108

 

Phone: (303) 688-9175

Fax: (303) 380-3338

 

E-mail:    

tim@skyview-wx.com

 

We’re on the Web!

http://www.skyview-wx.com/

 

Copyright 2009

Skyview Weather

2009-2010 Winter Outlook

The summer thunderstorm season is winding down now that we have reached September.  The spring and summer months have provided much needed moisture for the Front Range of Colorado which has resulted in above normal precipitation for many locations.  Could this be a sign of a cold and snowy winter to come or will the upcoming months feature warmer and drier than normal conditions? 

As far as this winter season is concerned the major player will be the onset of an “El Niño” cycle and the potential for above normal precipitation and snowfall for the 2009-2010 winter season.  Here’s what the NWS climate prediction center in Camp Springs, MD has to say about this upcoming El Niño:
 
CURRENT EL NINO CONDITIONS ARE EXPECTED TO STRENGTHEN AND PERSIST INTO THE BOREAL WINTER AND 2010. THE INCREASING LIKELIHOOD OF A CONTINUING EL NINO EVENT INFLUENCES THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR OND 2009 THROUGH MAM 2010. THE IMPACT OF EL NINO ON THE CLIMATE OVER NORTH AMERICA IS EXPECTED TO INCREASE FROM HAVING LITTLE OR NO IMPACT FOR SON 2009 TO THE GREATEST IMPACT DURING THE WINTER SEASONS. A WEAK TO MODERATE EL NINO EVENT IS EXPECTED DURING WINTER, THOUGH A STRONGER EVENT IS POSSIBLE…

With an El Niño expected this winter there will be a lot of hype about the potential for heavy snow and numerous large snow storms or blizzards.  Past El Niño years have certainly proved to be wet and snowy but there are also El Niño years that do not produce above normal precipitation.  Why does this happen?  It happens because of Colorado’s central location in the middle of a continent and the blocking effect of the Continental Divide for areas east of the Rockies.  In summary El Niño typically energizes the southern jet stream leaving the northern tier of states relatively dry and mild while the southern states often experience above normal precipitation with normal to slightly below normal temperatures.  Conversely, La Niña winters typically produce a more active northern jet stream with colder and wetter conditions in northern states with Colorado located on the line where some winters are cold and snowy while others may be drier, but close to normal or above normal in temperature.  Colorado’s location east of the Rockies requires the need for gulf moisture to energize our snow storms.  Since El Niño develops in response to rising Pacific Ocean temperatures and additional moisture is provided by the warmer water, but most of this moisture is actually “wrung” out over the Rocky Mountains west of the Continental Divide.  The active southern jet stream will provide the disturbances necessary for producing snow east of the Rockies, but the moisture for big snow storms still has to come from the Gulf of Mexico.  The track and speed of these storm systems determine how much gulf moisture and for long of a period of time it will affect the eastern parts of Colorado.  This is why “upslope” easterly/northeasterly winds are important as this wind direction at the surface imports moisture from the east that has originated from the gulf and pushes it up against the Front Range. The storm track can also drop too far south to provide Colorado with necessary “upslope” to generate snowfall thus drier than normal conditions may develop even in an El Niño year. 

As is always the case in Colorado predicting exactly what to expect this upcoming winter is a very difficult if not impossible task, but the trend of active weather over the past few months and forecasts of a strengthening El Niño cycle it is Skyview Weather’s belief is that this winter will feature above normal snowfall and above normal precipitation with near normal to slightly above normal temperatures.  There will likely be a few larger snow storms one of which is expected early in the winter in late October or November with one or two famous Colorado blizzards in the late winter or spring.  Snowfall frequency will likely be near normal to slightly above normal with the above normal precipitation expected to come from high moisture content snowfall as arctic air masses may not be as frequent this winter.  Typical snowfall for the Denver area is around 60” at old Stapleton Airport with around 70-75” of snow expected this upcoming winter with much higher amounts in the surrounding foothills and Palmer Divide areas. 

Drought Update

With the widespread precipitation of the last several months, little areas of drought remain in Colorado, though some dry areas have developed in Western Colorado.

The map below shows forecasted temperature deviances for September 2009. As can be seen, it is expected that much of Colorado to have  normal temperatures for the month of September 2009, with far southwestern Colorado expected to have above normal temperatures. 

The map below shows forecasted precipitation deviances for September 2009.  All of Colorado is expected to have normal precipitation for September 2009.

Little in the way of drought remains in Colorado, with no changes expected.

August Summary

August of 2009 was fairly benign compared to the previous months of spring and summer as precipitation was below average for the first time since March.  There was 1.14" of precipitation measured at DIA compared to 1.82" on average which was 0.68" below normal.  For the year there is still a surplus of 4.03" with 15.08" total so far this year.  Making the top ten in yearly precipitation is still not out of the question, but the upcoming fall and winter months will have to produce above normal precipitation to get close.  Temperatures continued to be below normal which has been consistent  this summer with the monthly mean temperature 1.3 degrees below normal.  Sunshine has been at a premium this this summer and in August the possible percent sunshine was 66% compared to 71% normally.  

August Stats

TEMPERATURE (IN DEGREES F)

 

 

 

 

 

 

AVERAGE MAX

85.6

NORMAL

86.0

DEPARTURE

-0.5

AVERAGE MIN

55.1

NORMAL

57.4

DEPARTURE

-2.3

MONTHLY MEAN

70.4

NORMAL

71.7

DEPARTURE

-1.3

HIGHEST

98 on the 23rd

LOWEST

47 on the 16th and 17th

 

 

 

 

 

 

DAYS WITH MAX 90 OR ABOVE

9

NORMAL

9.3

DAYS WITH MAX 32 OR BELOW

0

NORMAL

0

DAYS WITH MIN 32 OR BELOW

0

NORMAL

0

DAYS WITH MIN ZERO OR BELOW

0

NORMAL

0

 

 

 

 

 

 

TEMPERATURE RECORDS

 

Tied record low of 47 on the on the 16th set back in 1978

Tied record high of 98 on the 23rd set back in 1878

 

 

 

 

 

 

HEATING DEGREE DAYS

 

 

 

 

 

 

MONTHLY TOTAL

9

NORMAL

9

DEPARTURE

0

SEASONAL TOTAL

22

NORMAL

10

DEPARTURE

12

 

 

 

 

 

 

COOLING DEGREE DAYS

 

 

 

 

 

 

MONTHLY TOTAL

180

NORMAL

217

DEPARTURE

-37

YEARLY TOTAL

455

NORMAL

639

DEPARTURE

-184

 

 

 

 

 

 

PRECIPITATION (IN INCHES)

 

 

 

 

 

 

MONTHLY TOTAL

1.14

NORMAL

1.82

DEPARTURE

-0.68

YEARLY TOTAL

15.08

NORMAL

11.05

DEPARTURE

4.03

GREATEST IN 24 HOURS

0.47" on the 6th

DAYS WITH MEASURABLE PRECIPITATION

8

 

 

 

 

 

SNOWFALL (IN INCHES)

 

 

 

 

 

 

MONTHLY TOTAL

0

NORMAL

1.3

DEPARTURE

-1.3

SEASONAL TOTAL

38.1

NORMAL

61.7

DEPARTURE

-23.6

GREATEST IN 24 HOURS

NA

GREATEST DEPTH

NA

 

 

 

 

 

 

WIND (IN MILES PER HOUR)

 

 

 

 

 

 

AVERAGE SPEED

8.6 mph

PEAK WIND GUST

47 mph from the Southwest

 

 

 

 

 

 

MISCELLANEOUS WEATHER

 

 

 

 

 

 

NUMBER OF DAYS WITH THUNDERSTORMS

11

NORMAL

8

NUMBER OF DAYS WITH HEAVY FOG

0

NORMAL

1

NUMBER OF DAYS WITH HAIL

1

 

 

PERCENT OF SUNSHINE

66%

NORMAL

71%

September Preview

September can be one of the nicest months of the calendar year recording more sunshine than any other month and comfortable temperatures in the 70s and 80s.  The beginning of the month is quite often when most of the precipitation falls as the summer thunderstorm season comes to an end during September.  Monthly precipitation is around 1.14" with 6 days on average producing rainfall or snowfall for that matter as Denver averages 2.1" of snow for the month.  Don't get too excited about snow in September as the last 8 years have not produced any, but this year is a little different and would not be surprised to see some accumulating snow late this month.  Unbelievably, the monthly record snowfall is 17.2" set back in 1971 and the record low is 17 degrees set back in 1985.  These records indicate that winter can certainly make an appearance in September and produce plant killing cold and branch breaking snow.  More years than not though no snow accumulations greater than a trace are reported.  September is typically when the Front Range experiences the first freeze/frost as September averages one day during the month with a low of freezing or below.

 

DENVER'S NOVEMBER CLIMATOLOGICALLY NORMAL

(NORMAL PERIOD 1971-2000)

 

 

TEMPERATURE

 

 

 

AVERAGE HIGH

77.4

AVERAGE LOW

47.3

MONTHLY MEAN

62.4

DAYS WITH HIGH 90 OR ABOVE

2

DAYS WITH HIGH 32 OR BELOW

Less than 1

DAYS WITH LOW 32 OR BELOW

1

DAYS WITH LOWS ZERO OR BELOW

0

 

 

PRECIPITATION

 

 

 

MONTHLY MEAN

1.14"

DAYS WITH MEASURABLE PRECIPITATION

6

AVERAGE SNOWFALL IN INCHES

2.1

DAYS WITH 1.0 INCH OF SNOW OR MORE

Less than 1

 

 

MISCELLANEOUS AVERAGES

 

 

 

HEATING DEGREE DAYS

136

COOLING DEGREE DAYS

57

WIND SPEED (MPH)

7.9 mph

WIND DIRECTION

South

DAYS WITH THUNDERSTORMS

4

DAYS WITH DENSE FOG

1

PERCENT OF SUNSHINE POSSIBLE

74%

 

 

EXTREMES

 

 

 

RECORD HIGH

97 degrees on multiple dates

RECORD LOW

17 degrees on 9/29/1985

WARMEST

68.3 degrees in 1948

COLDEST

54.8 degrees in 1912

WETTEST

4.67" in 1961

DRIEST

Trace in 1944 and 1892

SNOWIEST

17.2" in 1971

LEAST SNOWIEST

0.0"  83 years with no snow
 

Sunrise/Sunset (Jul - December Denver area)

              JUL                AUG                SEP            OCT               NOV            DEC
______________________________________________________________________________
            sr - ss            sr - ss             sr - ss          sr - ss             sr - ss           sr - ss
 01  0535-0831 | 0559-0813 | 0628-0732 | 0656-0643 | 0629-0457 | 0702-0436  01
 02  0536-0831 | 0600-0812 | 0629-0730 | 0657-0641 | 0630-0456 | 0703-0435  02
 03  0536-0831 | 0601-0811 | 0630-0729 | 0658-0640 | 0631-0455 | 0704-0435  03
 04  0537-0831 | 0601-0810 | 0630-0727 | 0659-0638 | 0632-0454 | 0705-0435  04

 05  0538-0831 | 0602-0809 | 0631-0725 | 0700-0637 | 0633-0453 | 0706-0435  05
 06  0538-0830 | 0603-0808 | 0632-0724 | 0701-0635 | 0634-0452 | 0706-0435  06
 07  0539-0830 | 0604-0807 | 0633-0722 | 0702-0634 | 0635-0451 | 0707-0435  07
 08  0539-0830 | 0605-0805 | 0634-0721 | 0703-0632 | 0637-0450 | 0708-0435  08

 09  0540-0830 | 0606-0804 | 0635-0719 | 0704-0630 | 0638-0449 | 0709-0435  09
 10  0541-0829 | 0607-0803 | 0636-0717 | 0705-0629 | 0639-0448 | 0710-0435  10
 11  0541-0829 | 0608-0802 | 0637-0716 | 0706-0627 | 0640-0447 | 0711-0435  11
 12  0542-0828 | 0609-0800 | 0638-0714 | 0707-0626 | 0641-0446 | 0711-0435  12

 13  0543-0828 | 0610-0759 | 0639-0712 | 0708-0624 | 0642-0445 | 0712-0436  13
 14  0544-0827 | 0611-0758 | 0640-0711 | 0709-0623 | 0643-0444 | 0713-0436  14
 15  0544-0827 | 0612-0757 | 0641-0709 | 0710-0621 | 0644-0444 | 0714-0436  15
 16  0545-0826 | 0613-0755 | 0642-0708 | 0711-0620 | 0646-0443 | 0714-0436  16

 17  0546-0826 | 0614-0754 | 0643-0706 | 0712-0618 | 0647-0442 | 0715-0437  17
 18  0547-0825 | 0615-0752 | 0644-0704 | 0713-0617 | 0648-0442 | 0715-0437  18
 19  0547-0824 | 0616-0751 | 0644-0703 | 0714-0615 | 0649-0441 | 0716-0438  19
 20  0548-0824 | 0616-0750 | 0645-0701 | 0715-0614 | 0650-0440 | 0717-0438  20

 21  0549-0823 | 0617-0748 | 0646-0659 | 0716-0613 | 0651-0440 | 0717-0439  21
 22  0550-0822 | 0618-0747 | 0647-0658 | 0717-0611 | 0652-0439 | 0718-0439  22
 23  0551-0821 | 0619-0745 | 0648-0656 | 0719-0610 | 0653-0439 | 0718-0440  23
 24  0552-0821 | 0620-0744 | 0649-0654 | 0720-0609 | 0654-0438 | 0718-0440  24

 25  0552-0820 | 0621-0742 | 0650-0653 | 0721-0607 | 0656-0438 | 0719-0441  25
 26  0553-0819 | 0622-0741 | 0651-0651 | 0722-0606 | 0657-0437 | 0719-0441  26
 27  0554-0818 | 0623-0739 | 0652-0650 | 0723-0605 | 0658-0437 | 0720-0442  27
 28  0555-0817 | 0624-0738 | 0653-0648 | 0724-0603 | 0659-0436 | 0720-0443  28

 29  0556-0816 | 0625-0736 | 0654-0646 | 0725-0602 | 0700-0436 | 0720-0444  29
 30  0557-0815 | 0626-0735 | 0655-0645 | 0726-0600 | 0701-0436 | 0720-0444  30
 31  0558-0814 | 0627-0733 |                      | 0727-0558 |                      | 0720-0445  31

 

 Rainfall

May 2009 to October 2009

City

May

June

July

Aug Sept

Seasonal Totals

Aurora (Central)

2.99 4.06 4.25 1.65   12.95
Brighton 2.13 4.02 3.07 0.51   9.73
Broomfield 1.38 1.69 1.34 0.35   4.76

Castle Rock 4 NE

2.20 2.09 2.87 0.98   5.27

Colorado Sprgs Airport

1.17 2.91 3.82 0.71   8.61
Denver DIA 1.30 4.86 3.56 1.14   10.86

Denver Downtown

3.15 3.07 2.56 0.83   9.61

Golden

2.68 3.15 2.62 0.79   9.24

Fort Collins

2.24 4.85 4.04 0.23   11.36

Highlands Ranch

3.23 2.28 3.07 1.50   10.08

Lakewood

3.90 3.90 3.07 1.06   11.93

Littleton

3.15 3.19 2.48 1.10   9.92

Parker

1.81 4.33 3.66 0.59   10.39

Sedalia - Hwy 67

2.40 3.54 4.09 0.79   10.82

Thornton

2.17 2.64 1.89 0.39   7.09

Westminster

2.77 3.92 2.55 0.85   10.09

Wheatridge

2.44 3.19 2.44 0.67   8.75