The Weather Wire

 

July 2010                                                                                                            Volume 17 Number 07

 

Contents

 

 

 
·   "Dry" Thunderstorms
 

·   Drought Monitor

 

·   June

    Summary

 

·   June Stats

 

·   July Preview

 

·   Sunrise/Sunset

 

·   Precipitation Totals

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

June

Avg High - 84.1

Avg Low - 53.6

Snow - 0.0"

Season Snow - 60.6"

Precipitation - 1.60"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

July

Avg High - 88.0

Avg Low - 58.7

Avg Snow -  0.0"

Avg Precip - 2.16"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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 2010

Skyview Weather

Dry Thunderstorms/Outflow Boundaries

Not all thunderstorms in Colorado produce measurable rainfall as all it takes to be considered a thunderstorm is the presence of lightning and thunder.  There are many days along the Front Range of Colorado where there is limited moisture and yet enough instability to produce high based thunderstorms.  What is meant by “high based” is the bottom of the cloud has formed well above the surface, usually 8,000 feet or more above ground level.  The greater the distance from cloud bottom to the ground the greater the evaporation of the rainfall before it reaches the surface and in many cases there is not any rainfall left at all.  This time of year from late June into mid or late July is one of the most common times of year for “dry thunderstorms”.  This is mainly due to the changing of seasons as the cool of spring has left and the heat of summer is upon us yet the monsoonal moisture has not arrived from the desert southwest quite yet.  Once deeper moisture arrives later this month the threat of dry thunderstorms will lower through August until we transition into fall.  Then as monsoon moisture departs the state dry thunderstorms will be likely once again by early to mid September.    

Some of you have heard us as at Skyview Weather talk about temperature and dew point spreads.  What we are referring to is the air temperature and dew point at the surface which is a good indicator how much evaporation will occur as well as how strong the potential wind gusts will be.  At the base of the cloud temperature and dew point are the same, hence condensation occurs and clouds form.  While at the surface there may be upwards of a 50-60 degree temperature and dew point spread.  For example if it is 90 degrees outside and a current dew point of 30 degrees there is a spread of 60 degrees.  This magnitude of 60 can be used to predict potential wind speeds or gusts from thunderstorms; in this case a 60 mph wind gust is highly likely.  These wind gusts are caused by the evaporation of rainfall aloft cooling the air around it.  This cooler air rushes to the surface and spreads out from a central point.  These winds can travel quite a long distance slowly weakening the further away from the central point.  These winds as they spread out can be known as outflow boundaries.  Outflow boundaries can then push against the foothills or slam against another outflow boundary from another storm and can be a triggering mechanism for new thunderstorm development.  Many times these outflow boundary driven storms are “popcorn” type thunderstorms as they often strengthen and weaken rapidly.  Many times outflow boundaries and their associated winds can be surprising to some.  They can be that gust of wind out of nowhere while having that outdoor bbq, playing golf, fly-fishing, setting up that big outdoor tent, etc.

 

 Drought Update

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

The map below shows forecasted temperature deviances for July 2010. As can be seen, normal temperatures are expected the eastern 2/3s of Colorado with above average temperatures the western 1/3 of the state. 

The map below shows forecasted precipitation deviances for July 2010.  Normal precipitation is expected for the eastern 2/3s of Colorado with below normal precipitation the western 1/3 of the state.

Little in the way of drought remains in Colorado.

July Summary

July of 2010 was very wet for most areas of the Front Range as DIA reported 3.70” of precipitation for the month and 13 days with measureable rainfall.  Normal precipitation for DIA is 2.16” and with a surplus of 1.54” for July we are now 0.25” above normal for the year.  This July missed out on being in the top ten wettest July’s ever recorded by only 0.01” out of 10th place.  What a difference a month can make!  July of 2010 was also a little warmer than average with a mean temperature of 74.4 degrees compared to 73.4 on average.  There were 18 days with high temperatures of 90 degrees or more with 15 days during an average July.

June Stats

TEMPERATURE (IN DEGREES F)

 

 

 

 

 

 

AVERAGE MAX

84.1

NORMAL

82.1

DEPARTURE

2.0

AVERAGE MIN

53.6

NORMAL

53.0

DEPARTURE

0.6

MONTHLY MEAN

68.8

NORMAL

67.6

DEPARTURE

1.2

HIGHEST

99 on the 25th

LOWEST

47 on the 12th, 14th, 18th and 23rd

 

 

 

 

 

 

DAYS WITH MAX 90 OR ABOVE

10

NORMAL

6.3

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

 

No new temperature records tied or broken

 

 

 

 

 

 

 

HEATING DEGREE DAYS

 

 

 

 

 

 

MONTHLY TOTAL

38

NORMAL

60

DEPARTURE

-22

SEASONAL TOTAL

6441

NORMAL

6128

DEPARTURE

313

 

 

 

 

 

 

COOLING DEGREE DAYS

 

 

 

 

 

 

MONTHLY TOTAL

163

NORMAL

136

DEPARTURE

27

YEARLY TOTAL

179

NORMAL

161

DEPARTURE

18

 

 

 

 

 

 

PRECIPITATION (IN INCHES)

 

 

 

 

 

 

MONTHLY TOTAL

1.60

NORMAL

1.56

DEPARTURE

0.4

YEARLY TOTAL

5.80

NORMAL

7.09

DEPARTURE

-1.29

GREATEST IN 24 HOURS

1.25" from 6/11 to 6/12

DAYS WITH MEASURABLE PRECIPITATION

5

 

 

 

 

 

SNOWFALL (IN INCHES)

 

 

 

 

 

 

MONTHLY TOTAL

0.0

NORMAL

0.0

DEPARTURE

0.0

SEASONAL TOTAL

60.6

NORMAL

62.3

DEPARTURE

-1.7

GREATEST IN 24 HOURS

NA

GREATEST DEPTH

NA

 

 

 

 

 

 

WIND (IN MILES PER HOUR)

 

 

 

 

 

 

AVERAGE SPEED

9.8 mph

PEAK WIND GUST

46 mph from the SSW

 

 

 

 

 

 

MISCELLANEOUS WEATHER

 

 

 

 

 

 

NUMBER OF DAYS WITH THUNDERSTORMS

8

NORMAL

10

NUMBER OF DAYS WITH HEAVY FOG

3

NORMAL

<1

NUMBER OF DAYS WITH HAIL

1

 

 

PERCENT OF SUNSHINE

NA

NORMAL

70%

August Preview

August is typically the last month of true “summer” along the Front Range as temperatures towards the end of the month begin to fall off and thunderstorms become less likely.  Upper level winds are typically quite light this month reducing the necessary wind shear for severe storms with slow moving moderate and heavy rainfall producing thunderstorms being most likely which are fed by monsoonal moisture being drawn northward from the Desert Southwest.  The average high for August is 86.0 and the average low is 57.4 producing a monthly mean temperature of 71.7 which is cooler than July.  Average precipitation for the month is 1.82” with 9 days of measureable precipitation.  The record high for the month is 105 degrees which is tied for the hottest in Denver history and the record low is 40.  August of 2010 will likely be around normal in both precipitation and temperature.       

 

DENVER'S NOVEMBER CLIMATOLOGICALLY NORMAL

(NORMAL PERIOD 1971-2000)

 

 

TEMPERATURE

 

 

 

AVERAGE HIGH

88.0

AVERAGE LOW

58.7

MONTHLY MEAN

73.4

DAYS WITH HIGH 90 OR ABOVE

15

DAYS WITH HIGH 32 OR BELOW

0

DAYS WITH LOW 32 OR BELOW

0

DAYS WITH LOWS ZERO OR BELOW

0

 

 

PRECIPITATION

 

 

 

MONTHLY MEAN

2.16"

DAYS WITH MEASURABLE PRECIPITATION

9

AVERAGE SNOWFALL IN INCHES

0

DAYS WITH 1.0 INCH OF SNOW OR MORE

0

 

 

MISCELLANEOUS AVERAGES

 

 

 

HEATING DEGREE DAYS

1

COOLING DEGREE DAYS

261

WIND SPEED (MPH)

8.3 mph

WIND DIRECTION

South

DAYS WITH THUNDERSTORMS

11

DAYS WITH DENSE FOG

<1

PERCENT OF SUNSHINE POSSIBLE

71%

 

 

EXTREMES

 

 

 

RECORD HIGH

105 on 7/20/2005

RECORD LOW

42 on 7/4/1903, 7/31/1873

WARMEST

77.8 in 1934

COLDEST

67.4 in 1895

WETTEST

6.41" in 1965

DRIEST

0.01" in 1901

SNOWIEST

No snow ever recorded

LEAST SNOWIEST

No snow ever recorded
 

Sunrise/Sunset (July - Dec Denver area)

                 JUL            AUG           SEP              OCT            NOV          DEC
______________________________________________________________________________
           sr - ss           sr - ss          sr - ss           sr - ss           sr - ss           sr - ss
 01  0535-0831 | 0558-0813 | 0627-0732 | 0656-0643 | 0728-0558 | 0701-0436  01
 02  0536-0831 | 0559-0812 | 0628-0731 | 0657-0642 | 0729-0556 | 0702-0435  02
 03  0536-0831 | 0600-0811 | 0629-0729 | 0658-0640 | 0731-0555 | 0703-0435  03
 04  0537-0831 | 0601-0810 | 0630-0727 | 0659-0639 | 0732-0554 | 0704-0435  04

 05  0537-0831 | 0602-0809 | 0631-0726 | 0700-0637 | 0733-0553 | 0705-0435  05
 06  0538-0831 | 0603-0808 | 0632-0724 | 0701-0635 | 0734-0552 | 0706-0435  06
 07  0539-0830 | 0604-0807 | 0633-0723 | 0702-0634 | 0635-0451 | 0707-0435  07
 08  0539-0830 | 0605-0806 | 0634-0721 | 0703-0632 | 0636-0450 | 0708-0435  08

 09  0540-0830 | 0606-0804 | 0635-0719 | 0704-0631 | 0637-0449 | 0709-0435  09
 10  0541-0829 | 0607-0803 | 0636-0718 | 0705-0629 | 0639-0448 | 0710-0435  10
 11  0541-0829 | 0608-0802 | 0637-0716 | 0706-0628 | 0640-0447 | 0710-0435  11
 12  0542-0828 | 0609-0801 | 0638-0715 | 0707-0626 | 0641-0446 | 0711-0435  12

 13  0543-0828 | 0610-0759 | 0639-0713 | 0708-0625 | 0642-0445 | 0712-0436  13
 14  0543-0827 | 0611-0758 | 0640-0711 | 0709-0623 | 0643-0445 | 0713-0436  14
 15  0544-0827 | 0612-0757 | 0641-0710 | 0710-0622 | 0644-0444 | 0713-0436  15
 16  0545-0826 | 0612-0755 | 0641-0708 | 0711-0620 | 0645-0443 | 0714-0436  16

 17  0546-0826 | 0613-0754 | 0642-0706 | 0712-0619 | 0646-0442 | 0715-0437  17
 18  0546-0825 | 0614-0753 | 0643-0705 | 0713-0617 | 0648-0442 | 0715-0437  18
 19  0547-0825 | 0615-0751 | 0644-0703 | 0714-0616 | 0649-0441 | 0716-0437  19
 20  0548-0824 | 0616-0750 | 0645-0701 | 0715-0614 | 0650-0440 | 0716-0438  20

 21  0549-0823 | 0617-0749 | 0646-0700 | 0716-0613 | 0651-0440 | 0717-0438  21
 22  0550-0822 | 0618-0747 | 0647-0658 | 0717-0612 | 0652-0439 | 0717-0439  22
 23  0551-0822 | 0619-0746 | 0648-0656 | 0718-0610 | 0653-0439 | 0718-0439  23
 24  0551-0821 | 0620-0744 | 0649-0655 | 0719-0609 | 0654-0438 | 0718-0440  24

 25  0552-0820 | 0621-0743 | 0650-0653 | 0720-0608 | 0655-0438 | 0719-0441  25
 26  0553-0819 | 0622-0741 | 0651-0652 | 0722-0606 | 0656-0437 | 0719-0441  26
 27  0554-0818 | 0623-0740 | 0652-0650 | 0723-0605 | 0657-0437 | 0719-0442  27
 28  0555-0817 | 0624-0738 | 0653-0648 | 0724-0604 | 0658-0437 | 0720-0443  28

 29  0556-0816 | 0625-0737 | 0654-0647 | 0725-0602 | 0659-0436 | 0720-0443  29
 30  0557-0815 | 0626-0735 | 0655-0645 | 0726-0600 | 0700-0436 | 0720-0444  30
 31  0558-0814 | 0627-0734 |                   | 0727-0559 |                    | 0720-0445  31



Precipitation

May 2010 to Sept 2010

City

May

June

July

Aug

Sept

Seasonal Totals

Aurora (Central)

1.02 2.32       3.34
Brighton 2.83 4.06       6.89
Broomfield 1.50 1.54       3.04

Castle Rock 4 NE

0.63 1.30       1.93

Colorado Sprgs Airport

0.82 0.34       1.16
Denver DIA 1.52 1.60       3.12

Denver Downtown

2.09 1.81       3.90

Golden

1.61 3.29       4.90

Fort Collins

1.97 1.74       3.71

Highlands Ranch

1.10 2.24       3.34

Lakewood

1.42 1.46       2.88

Littleton

1.22 1.89       3.11

Parker

0.79 1.54       2.33

Sedalia - Hwy 67

0.98 2.28       3.26

Thornton

1.91 2.48       4.39

Westminster

1.26 2.17       3.43

Wheatridge

1.50 1.65       3.15