How do the 50's sound for Wednesday and Thursday nights in the suburbs? While the Mid-Atlantic region just experienced a pretty impressive week-long heat wave, the summer so far has been rather ordinary when it comes to the number of hot days, and it appears that the worst of the heat may already be over. Since the latter part of May and through yesterday, July 22nd, Philadelphia has had 19 days in the 90’s compared to the average of 27 days. DC has had 20 days of 90 degrees or above so far this summer versus an average summer of 36 days by this date. Central Park in New York City, which peaked last week at 98 degrees during the heat wave, has had only 15 days of 90 degrees or above since late May.
One of the factors that is likely inhibiting prolonged excessive heat in the Mid-Atlantic region this summer is the high soil moisture content which remains following the excessive rainfall (~10 inches) that fell during the month of June in DC, NYC, Philly. High soil moisture content can knock off a few degrees from potential high temperatures as some of the sun’s energy is used up in evaporation processes rather than in heating the ground directly which in turn heats the lower atmosphere (i.e., more likely to experience prolonged heat waves in drought conditions).
As far as the rest of the summer is concerned in the Mid-Atlantic region, there are signs pointing to a cooler-than-normal finish to the month of July, and even perhaps a cooler-than-normal month of August. An upper level trough of low pressure will likely prevail in the East over the coming weeks while ridging (and hot weather) dominates in the West. Last week’s heat wave in the Mid-Atlantic may very well have been the hottest weather we’ll experience all summer long in this region.
As far as the tropics are concerned, it is quite unusual to be at this stage of the summer and find that there is no tropical storm in either the Atlantic or Pacific Ocean. It is quite likely, however, that the tropics will become more active in the weeks to come as they’ll typically peak during the month of September.