MUWIC Newsletter - August 2003

(Issued: July 31, 2003)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: “Extreme Heat a No-Show”

With two-thirds of the Summer behind us, it’s looking increasingly likely that we will be spared any extreme heat. Through the end of July, there have only been six days with high temperatures in the 90s. By the end of July last year, the Lancaster area had already reached this benchmark 27 times. The normal number of 90-degree days through the end of July is sixteen.

Interestingly, the summer so far has not been particularly cool overall. In fact, when you average in the overnight low temperatures--which have been warmer than normal due to high humidity and persistent cloudiness--the average temperature for the summer falls very close to normal. So, while there has been a marked lack of extreme heat this summer, daily high and low temperatures actually average “near normal.”

The rest of the summer will likely continue the same story line. A mean jet stream trough over the eastern third of the country should hang on, while the Bermuda high slowly builds westward toward the East coast. These two features should produce frequent bouts of high humidity, clouds, and scattered showers. If so, it’s likely we’ll continue to see only occasional 90-degree days and no long-term spells of hot, dry conditions.

90-Degree Days (MU Weather Station):

Normal 2002 2003

April 0.5 3 0

May 1.5 0 0

June 5 6 3

July 9 18 3

August 6 16 ?

September 2 2 ?

Total 24 45 6 (7/31)

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EVENT OF THE MONTH

Severe thunderstorms crossed the northern and central part of Lancaster county on July 21^st. Heavy downpours, high wind gusts, and small hail damaged trees and power lines in some neighborhoods north of Route 23.

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STAT OF THE MONTH

A thunderstorm dropped 1.34 inches of rain on Millersville in just one hour on July 23^rd. This is more rain than fell during the entire month of July last year (0.74”).

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JULY CLIMATOLOGY (MU Weather Station)

Average High Temp: -1.8 F

Average Low Temp: +2.9 F

Average Monthly Temp: 75.5 F

(Departure from Normal: +0.6 F)

Precipitation: 3.49 inches

(Departure from Normal: -1.02)

Annual Precipitation: 23.33 inches

(Departure from Normal: -2.01)

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AUGUST NORMALS, RECORDS & FACTS

Normal high/low temperatures decrease from 86/63 on August 1st to 83/59 by month’s end. The record high for August is 107 degrees set on the 7th of 1918, while the record low is 35 F set on the 29th in 1982. Normal liquid precipitation for the month is 3.97 inches. The rainiest August on record (13.94 inches) occurred in 1933. The driest August was in 1957 when only 0.51 inches fell.

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AUGUST OUTLOOK

Looking ahead to August, I see the Bermuda high pressure system nearing the east coast with more persistent humidity and occasional shower threats. Despite this development, a bonafide heatwave is doubtful due to the persistent jet stream trough centered in the Mississippi and Ohio Valleys. This feature will send frequent disturbances our way with occasional clouds and showers. Consequently, any hot spells will be short lived, but periods of high humidity will not. The developing Bermuda high should pump plentiful maritime tropical air into the eastern US, so get used to the muggies.

Of course, we'll need to keep an eye on the tropics as storminess becomes more frequent as September (the most active month) nears. It’s possible that a tropical storm or hurricane will form in the Atlantic by late month and eventually track toward the mean trough position over the eastern US. Such a storm could bring a soaking rain to any states in its path. Given the current pattern, it is my sense that we have a greater than normal chance of experiencing the remains of a tropical storm or hurricane sometime in the next 60 days. With rainfall just shy of normal (year-to-date), such a soaking rain might not be such a bad thing.