The Weather Wire

 

May 2007                                                                                                            Volume 15 Number 05

 

Contents

 

·   Lightning Season

 

·   Drought Monitor

 

·   April

    Summary

 

·   April Stats

 

·   May Preview

 

·   Sunrise/Sunset

 

·   Snow Totals

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

April 2007

 

Avg High 59.9

Avg Low 33.6

Snow - 0.9"

Season Snow - 72.6"

Precipitation - 2.65"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

May

Avg High 70.5

Avg Low 43.8

Avg Snow -  1.3"

Avg Precip - 2.32"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Skyview Weather 

2350 Rocky View Rd

Castle Rock, CO 80108

 

Phone: (303) 688-9175

Fax: (303) 660-0548

 

E-mail:    

tim@skyview-wx.com

 

We’re on the Web!

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

 

Copyright 2007

Skyview Weather

Lightning Season Again!!!

Yes it is that time of year again! Usually March brings the first claps of thunder and the first bolts of lightning. If not in March, definitely in April and May.  On average some 20 million bolts of lightning strike the U.S. during a single year.  Of these over half strike the ground at more than one point.  So we have at a minimum 30 million spots struck by lightning each year!  That is a lot of lightning!  The lightning capital of the nation is Florida, but Colorado is not far behind.  This is due to our closeness to the mountains to our west.  The mountains help to trigger thunderstorms for our area spring through fall. A typical thunderstorm day for Colorado starts out with a sunny morning.  Clouds begin to develop on the mountains and foothills to the west.  As the clouds grow taller and develop into thunderstorms upper level steering winds push the storms out onto the plains.

Lightning is caused as rising air currents in the storms carry water droplets to areas of the clouds below freezing, where some of these droplets freeze.  It is in the mixture of water and ice that a charge develops.  When this charge is sufficiently large a bolt of lightning reaches from the cloud to the ground releasing large amounts of electricity.  In the tropics where the atmosphere is warmer to a higher altitude many storms can and do produce torrential rains but produce no lightning so having a low altitude freezing level such as we have here in Colorado increases the number of lighting strikes we see along the Front Range.  This low freezing level is also conducive to producing hail, which we see quite a bit of in eastern Colorado.

Cloud to ground lightning can kill or injure people by direct or indirect means.  The lightning current can branch off to a person from a tree, fence, pole or other tall object.  In addition, lighting strikes may conduct their current through the ground to a person after the lightning strikes a nearby tree, antenna or other tall object.  The current also may travel through power or telephone lines, or plumbing pipes to a person who is in contact with an electric appliance, telephone or plumbing fixture.  Now lets think about the golfer who is carrying a metal rod and wearing spikes shoes, not the best combination when there is lightning around!

During the past 30 years, lightning killed an average of 73 people per year in the United States based on documented cases. This is more than the average of 68 deaths per year caused by tornadoes and the average of 16 deaths per year caused by hurricanes. However, because lightning usually claims only one or two victims at a time, and because lightning does not cause the mass destruction left in the wake of tornadoes or hurricanes, lightning generally receives much less attention than the more destructive weather-related killers. While documented lightning injuries in the United States average about 300 per year, undocumented injuries caused by lightning are likely much higher.

One of the factors here in Colorado that causes a false sense of security and causes many people to stay out too long is our naturally dry air.  Many times thunderstorms develop, the rain falls from the clouds, but evaporates before it gets to the ground.  Lighting is still produced in these ‘dry’ thunderstorms, but with no rain to chase people indoors the tendency to stay outside until it is too late.  In addition lighting has been know to strike as far as 10 miles from the approaching stormSo just because it is not raining yet, does not mean you are safe from lightning!! You should always stay alert to changing weather conditions while you are outside and have a good idea where you will go if lighting becomes a threat. 

The most important statement for everyone to understand, memorize and act on is:  NO PLACE OUTSIDE IS SAFE FROM LIGHTING NEAR THUNDERSTORMS!!

Drought Update

Little change, or perhaps improvement, in overall drought conditions across Colorado occurred in April.

The map below shows forecasted temperature deviances for May 2007. As can be seen,  .normal  temperatures are expected for Colorado for May 2007.

The map below shows forecasted precipitation deviances for May 2007.  Normal precipitation is expected for  Colorado for May 2007.

As can be seen in the below map, drought improvement is forecast for portions of  far Northeast Colorado through July.  Some drought persistence will continue far Western Colorado.

April Summary

Between April 23 and 24, 2.10 inches of rainfall was recorded at DIA.  This is a 24 hour precipitation record surpassing the old record of 1.29 inches set back in 1891.  The month finished with a total of 2.65 inches which was 0.72 inch above normal.  So, now 3 of the past 5 months have been above normal in the moisture category.  April is Denver’s 3rd snowiest month.  However at the old Stapleton’s recording site only 0.9 inch was recorded.  Again most areas along the Front Range had much more snow than that!  We continue well above normal for the season with a total of 72.6 inches, 10.9 inches above the normal of 61.7.  Many areas of the western and southern suburbs are well above 100 inches for the season.

Temperatures during April 2007 ranged from a high of 83 degrees down to a low of 22 degrees.  The average temperature for the month was 46.8 degrees which was 0.8 degrees below normal.  The coldest April occurred in 1920 with an average temperature of 38.8 degrees.

April Stats

TEMPERATURE (IN DEGREES F)

 

 

 

 

 

 

AVERAGE MAX

59.9

NORMAL

60.9

DEPARTURE

-1.0

AVERAGE MIN

33.6

NORMAL

34.2

DEPARTURE

-0.6

MONTHLY MEAN

46.8

NORMAL

47.6

DEPARTURE

-0.8

HIGHEST

83 on the 28th

LOWEST

22 on the 12th

 

 

 

 

 

 

DAYS WITH MAX 90 OR ABOVE

0

NORMAL

0

DAYS WITH MAX 32 OR BELOW

1

NORMAL

LT 1

DAYS WITH MIN 32 OR BELOW

14

NORMAL

11

DAYS WITH MIN ZERO OR BELOW

0

NORMAL

.LT 0

 

 

 

 

 

 

TEMPERATURE RECORDS

 
 
None

 

 

 

 

 

 

HEATING DEGREE DAYS

 

 

 

 

 

 

MONTHLY TOTAL

544

NORMAL

524

DEPARTURE

20

SEASONAL TOTAL

5940

NORMAL

5801

DEPARTURE

139

 

 

 

 

 

 

COOLING DEGREE DAYS

 

 

 

 

 

 

MONTHLY TOTAL

5

NORMAL

2

DEPARTURE

3

YEARLY TOTAL

5

NORMAL

2

DEPARTURE

3

 

 

 

 

 

 

PRECIPITATION (IN INCHES)

 

 

 

 

 

 

MONTHLY TOTAL

2.65"

NORMAL

1.93"

DEPARTURE

0.72"

YEARLY TOTAL

4.13"

NORMAL

4.21

DEPARTURE

-0.08"

GREATEST IN 24 HOURS

2.10" on the 23rd/24th

DAYS WITH MEASURABLE PRECIPITATION

8

 

 

 

 

SNOWFALL (IN INCHES)

 

 

 

 

 

 

MONTHLY TOTAL

0.9"

NORMAL

9.1"

DEPARTURE

-8.2"

SEASONAL TOTAL

72.6"

NORMAL

61.7"

DEPARTURE

10.9"

GREATEST IN 24 HOURS

0.6" on the 9th

GREATEST DEPTH

1"

 

 

 

 

 

 

WIND (IN MILES PER HOUR)

 

 

 

 

 

 

AVERAGE SPEED

11.3

       

PEAK WIND GUST

52 from the South on 4/18

 

 

 

 

 

 

MISCELLANEOUS WEATHER

 

 

 

 

 

 

NUMBER OF DAYS WITH THUNDERSTORMS

2

 NORMAL

2

NUMBER OF DAYS WITH HEAVY FOG

4

 NORMAL

 1

NUMBER OF DAYS WITH HAIL

0

 

 

PERCENT OF SUNSHINE

68

NORMAL

67

 

 

 

May Preview

The weather in Denver is quite changeable throughout the year.  However, the month of May seems to feature the most changes from year to year, day to day or even hour to hour.  Denver’s May weather can include almost any type of weather.

Late season frosts can nip plant growth because the average date of the last freeze is May 5th, but the latest date of a Denver freeze is June 2.  On the other hand, afternoon temperatures in the 80s are common and the mercury occasionally climbs into the 90s.

May normally marks the beginning of the severe weather season.  Violent thunderstorms with large hail and tornadoes are possible.  These severe storms occur when moisture from the Gulf of Mexico moves into Colorado and collides with cold fronts still moving in from Canada or from the Pacific Northwest.

May is also the wettest month of the year and on average, precipitation normally occurs once every three days.  May is tied with November as having the lowest percentage of possible sunshine.

Snowfall in Denver during May is rare but does occur as we saw last May.  Denver’s high elevation intensifies late season cold air masses and on the average snow occurs in about two out of every five years.

DENVER'S MAY CLIMATOLOGICALLY NORMAL

(NORMAL PERIOD 1971-2000)

 

 

TEMPERATURE

 

 

 

AVERAGE HIGH

70.5

AVERAGE LOW

43.8

MONTHLY MEAN

57.2

DAYS WITH HIGH 90 OR ABOVE

LT 1

DAYS WITH HIGH 32 OR BELOW

0

DAYS WITH LOW 32 OR BELOW

2

DAYS WITH LOWS ZERO OR BELOW

0

 

 

PRECIPITATION

 

 

 

MONTHLY MEAN

1.93"

DAYS WITH MEASURABLE PRECIPITATION

11

AVERAGE SNOWFALL IN INCHES

1.3"

DAYS WITH 1.0 INCH OF SNOW OR MORE

0

 

 

MISCELLANEOUS AVERAGES

 

 

 

HEATING DEGREE DAYS

267

COOLING DEGREE DAYS

23

WIND SPEED (MPH)

9.3

WIND DIRECTION

SOUTH

DAYS WITH THUNDERSTORMS

6

DAYS WITH DENSE FOG

1

PERCENT OF SUNSHINE POSSIBLE

64

 

 

EXTREMES

 

 

 

RECORD HIGH

95 DEGREES ON 05/26/1942

RECORD LOW

19 DEGREES ON 05/03/1907

WARMEST

64.6 DEGREES IN 1934

COLDEST

48.7 DEGREES IN 1917

WETTEST

8.57" IN 1876

DRIEST

0.06" IN 1974

SNOWIEST

15.5" INCHES in 1898

LEAST SNOWIEST

0.0" multiple years

Sunrise/Sunset (Denver area)

     Date

Sunrise

Sunset

     May 1  

06:01

19:53

     May 5

05:56

19:57

     May 10

05:50

20:01

     May 15

05:45

20:06

     May 20

05:41

20:11

     May 25

05:37

20:15

     May 30

05:35

20:19

 Snowfall

October 2006 to April 2007

City

Oct

Nov

Dec

Jan Feb Mar Apr

Seasonal Totals

Aurora (Central)

16.2 4.0 31.1 17.8 8.8 5.6 0.0 83.5

Castle Rock 4 NE

 22.5 5.5 49.8 22.2 12.8 6.8 20.1 139.7

Colorado Sprgs Airport

6.1 3.5 8.3 6.6 1.8 0.1 3.8 30.0
Colorado Sprgs Woodman Rd 20.8 6.5 22.0 18.0 7.0 TR 7.0 81.3
Denver Stapleton  4.8 4.4 29.4 15.4 6.8 4.1 0.9 71.1

Denver Downtown

5.6 4.2 35.3 15.2 8.2 8.9 0.9 85.0

Golden

20.5 12.5 45.6 24.8 17.1 3.2 0.7 124.4

Highlands Ranch

19.0 5.0 42.0 24.8 13.5 11.0 9.5 124.8

Lakewood

13.3 5.0 32.0 18.3 10.8 3.6 1.0 84.0

Littleton

13.0 6.5 40.2 21.2 11.9 4.5 2.9 100.2

Louisville

 9.0 6.7 36.0 21.2 11.0 4.0 0.1 97.6

Parker

11.0 4.0 40.0 19.2 7.0 4.5 8.0 99.2

Sedalia - Hwy 67

13.0 4.5 38.8 28.0 18.0 9.6 11.3 133.9

Thornton

12.7 4.9 38.9 19.1 6.3 8.1 0.0 90.0

Westminster

13.9 5.3 40.4 21.5 9.1 7.0 0.0 97.2

Wheatridge

15.1 8.1 43.2 16.9 11.5 7.2 2.3 104.3