The Weather Wire
September 2004 Volume 11 Number 9
Avg High 82.4
Avg Low 54.0
Snow - 0.0"
Season Snow - 0.0"
Precipitation - 2.84"
Avg High 77.4
Avg Low 47.3
Avg Snow - 2.1"
Avg Precip - 1.14"
Heavy Snow Season on Tap??? |
After 3 months in a row of above normal precipitation and below normal temperatures we have to begin to ask ourselves if this pattern is expected to continue into the fall and winter months. The pattern that gave us our 5-6 years of drought was caused by a large persistent ridge of high pressure anchored over the central Rockies. With this high pressure area in that location storm systems went around us and took their precious moisture north, south and east of our region. The result has been very dry weather for Colorado.
We began to notice a change in this pattern last year and it began with the St. Paddy’s day blizzard in March of 2003. This blocking ridge of high pressure was beginning to show signs of shifting its position over the Rockies not only allowing more storms to move across the state during the fall and winter, but saw a return to a monsoon flow during the summer months and saw a net increase in thunderstorm activity for much of Colorado in the summer of 2003. We have seen this continue for the summer of 2004 with June, July and now August wetter than normal and cooler than normal.
Although we do not totally understand what causes 5,6,10 year weather patterns to change we can by studying the climatology of a region see that droughts affect our region of the country every 30-50 years for periods of 2-5 years in duration. In between major droughts we can see mini droughts lasting from less than a year to a little more than a year. And the rest of the time we see our moisture range from near normal to well above normal. Perhaps these long-term weather patterns are tied to minor changes in the sun, which is the engine that drives all the weather here on earth. Another factor to consider are the long and short-term changes in ocean temperatures that changes where high and low pressure areas develop not only over the ocean, but over the land masses as well. We are just now beginning to understand the effects that El Nino and La Nina have on our weather from the west coast to the Rockies. There does seem to be some correlation between these ocean currents and our wet and dry cycles here in the Rockies.
It is pretty safe to say at this point that we are now coming out of the drought pattern we’ve been in for the past 5 years into a wetter pattern that should persist for a number of years. This is not to say that the Front Range communities will not continue to have water problems. As we’ve said in numerous other articles the population increases along the Front Range will continue to put a strain on our water supplies even during good moisture years. It also doesn’t mean we will not see dry periods lasting from a week or two to perhaps a little over a month. Remember we live in a semi-arid climate.
Now as to snow for the coming season. Normal snowfall for the Denver area is about 60 inches a season. The foothills see quite a bit more on average and areas like the Springs see a bit less. If our current cool and wet weather pattern continues and right now there is no reason to think it won’t we would be looking at a normal to above normal snow season for the Front Range and foothills. The 2003 snow season saw a slightly below normal total for the season. So a good estimate for this year would be in the 60-80 inch range for the Front Range with slightly less for the Springs with perhaps 30-50 inches. I know this will make the skiers happy, but for those of you who have to plow it for a living, get ready for a busy year!
In many portions of Colorado, August 2004 continued to see above normal precipitation, particularly across Eastern Colorado. With the moisture, the drought situation improved across much of Colorado.
The map below shows forecasted temperature deviances for the September 2004 time period. As can be seen, above below normal temperatures are expected for all of Colorado for September.
The map below shows forecasted precipitation deviances for September 2004. Normal or near normal precipitation is expected forSeptember 2004 all of Colorado.
As can be seen in the below map, drought conditions are expected to continue to improvement across much of Colorado through November 2004.
It was a cool and wet August this year, which was quite different than the last 5 or 6 years. Temperatures ranged from a non-record 96 degrees on the 1st down to a record setting 42 degrees on the 28th. There were 5 temperature records either set or tied during the month, all of which involved low temperatures. The average temperature for August 2004 was 68.2 degrees tying for the 7th coldest with 1967. There were only 4 days where the high temperature reached into the 90s, compared to 19 days with 90 degrees or above in 2003. The normal amount of 90 degree days is 9. There were 31 heating degree days recorded which ties as the 3rd most with 1927. On the other hand there were 137 cooling degree days tallied which puts it at the top of the cooling degree list for least in August since cooling degree records began in 1969. Heating degree records go back to 1899.
Most Denverites were quite elated with the 2.84 inches of rainfall recorded during August of 2004. That was not enough to get into the top 10 wettest. The 10th wettest was recorded in 1908 with a total of 3.19 inches. The wettest ever August in Denver was 5.85 inches in 1979.
On August 18th heavy rains covered much of the Front Range and set a new 24 hour precipitation record for August 18th with a total of 1.62 inches. Many areas, especially along the foothills saw over 2 inches from this storm. The previous record for August 18th was 0,83 inch set in 1962. This was the third month in a row with above normal moisture, bringing our annual total to 12.07 inches which is now only 0.74 inches below normal for the year, Last year, 2003 we had 13.41 inches in the rain gage, but remember this included all the moisture from the St. Paddy’s day blizzard.
September is normally a sunny and pleasant month in Denver with the highest monthly percentage of sunshine for the year. The general weather pattern features Fall-like weather consisting of bright sunny days and clear cool nights.
Summer can linger as late as the end of the month. On September 30th 1980 a record was set when the temperature maxed out at 90 degrees. In fact the first 20 days of September all have record highs in the 90s. 97 degrees stands as the hottest temperature ever recorded during September and that occurred 4 different times, with the last 2 occurrences recorded on September 1st and 4th in 1955. Thunderstorms are still around in September, however they are less frequent and severe storms are rare.
Winter can also sneak in during September. The earliest measurable snowfall record occurred on September 3rd in 1961 when 4 inches of snow fell at the old Stapleton Airport and the temperature dropped to 33 degrees. The earliest freeze in Denver occurred on September 8th in 1962 with a recorded low temperature of 31 degrees. A real taste of early winter came in 1985 when on the 29th, 9 inches of snow fell on the city, the mercury dropped to a low of 17 degrees after reaching a high for the day of only 29 degrees. Both high and low temperatures set New records on the 29th of September.
Sunrise/Sunset (Denver area)