Monthly Summary: May 2003

May 2003 will be a month remembered as unusual for years. Nationally, 562 suspected tornadoes developed in the month. This count was the highest in a month ever for the United States. Although the weather was not nearly as severe in Pennsylvania, May 2003 will be remembered here as being unusual too.

May 2003 was an extremely rainy, cool, and cloudy month. These unusual conditions were caused by a several series of low-pressure systems being over the area. The following table shows how many days in May, out of the 31 possible, that precipitation fell as rain in various locations in the Commonwealth:

Table 1: The Number of Rainy Days in May 2003

	Number of Days in May
City	With Precipitation
Harrisburg	23
Philadelphia	22
Pittsburgh	23
State College	25

The month of May 2003 began promising. A warm front raised temperatures into the upper 70’s and lower 80’s throughout the state. A temperature of 87 degrees was reported in Renovo on the 2^nd. Little did we know then though, this observation would be the high for the entire month. In fact, the next day, the cold front associated with this low-pressure system came through, and cooled temperatures to below normal and produced precipitation. As the third day of May began, high pressure worked its way in from the west, bringing more pleasant temperatures and some sun to most of the state for the 4^th. Late on the fourth, a low-pressure system west of the Commonwealth moved near. Temperatures fell, and the pattern of gloomy weather began. In northerly Kane, temperatures fell to 27 degrees on the 4^th and 5^th. This low-pressure system west of the Commonwealth stalled and the warm front sat over our area for the next few days. Several tenths of rain fell.

After this low-pressure system moved away, several more low-pressure systems followed. This trend ended on the 11^th, when a well-developed low-pressure system moved in from the west. Clouds, rain, and high temperatures of the upper fifties moved in with this system. On the 13^th of May, high-pressure moved in from the west and provided some relief from the rain. However, this high-pressure did not bring much relief from the overcast skies and cool temperatures because it was closely flanked by the previous low-pressure system, now east of the Commonwealth, and another low-pressure system to the west.

This next low-pressure system moved in from the west on the 15^th. Temperatures warmed with the passing of the warm front, but cooled again once the cold front moved through. This system stalled over Pennsylvania, and the clouds and rain associated with it persisted through the 17^th. Finally on the 18^th, the system moved south and high pressure was able to move in. For the first time this month, the high-pressure area brought the clear skies and normal May temperatures that the people of Pennsylvania were waiting for.

This weather did not last long, however. On the 20^th the next series of low-pressure systems was just to the west of the state. Soon, temperatures returned to below normal, the skies clouded over, and precipitation fell again. This series began with a cold front that moved in from the west and reduced temperatures to back below normal. On the 23^rd, a trough of low pressure over Pennsylvania developed into a low-pressure system. Right after this system moved east, another system formed over us on the 28^th. The only respite in this weather was the 29^th. High pressure, wedged between two low-pressure systems, moved in and brought clear skies and warmer temperatures. But then the next low-pressure moved in, and the month ended, as it was most of the time: cloudy and wet.

-Lorri Bazzel

May 2003 Extreme Weather Data

		Town(s)	Date(s)
Max High Temp	87	Renovo	2
Min Low Temp	27	Kane	4, 5, 22
Max Rain	9.24	Chalk Hill
Min Rain	2.28	Covington