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Tuesday 8:30 a.m.
Drier air advanced into the northeast quarter of the nation yesterday, but its tenure is temporary and will be quickly terminated. As a high pressure area moves off the East Coast and a low pressure area forms near the lower Great Lakes, more humid air will be drawn northward... and the chance of showers and thunderstorms will increase. This looks like the kind of setup that can unleash 1-2 inches of rain in some areas. However, until we see exactly where the storm forms and how the moisture becomes arranged around it, forecasting rainfall amounts for various places is risky. The video has more.
On this date in 1918, Philadelphia had a high temperature of 106, the highest official reading ever for that city. What did the weather map look like that day? NOAA maintains an archive of weather maps for each day back to 1871. You can view them here The map for Aug. 7, 1918 is below. The map time is 1 a.m., and you may be able to see the 80-degree isotherm for that hour.
In those days, weather records were kept at the Customs House in Center City, Philadelphia. In later years, the observation site was shifted to Philadelphia International Airport. Airport locations are typically somewhat cooler than the middle of our big cities.
Tropical Storm Erika could eventually affect Florida and other sections of the Gulf Coast or Southeast, but for now it poses no threat for the Northeast. This map shows the storm as of early this morning.
The second concern is Erika. The map below shows what many different models area saying. While there is a good agreement in the short range, the longer-range spread is quite larger, with tracks ...
This picture shows where Erika is. The various models show a track toward Florida with a lot of uncertainty after that. If it does make it to land, then moves slowly (steering forces look weak), it could be a major rain producer.
It is way too early to be definitive about these storms, but the many models being used in predicting the track have closer agreement than many storms have at this point.
On this satellite picture, you can see a cold front approaching the Appalachians. That front helped produce thunderstorms in the Midwest yesterday, but that activity died out overnight. It is likely to reactivate today, with...
...shows a north-south trough line over New England. Moist air will approach this line from the southeast while northerly breezes bring in dry weather west of the line. As the front stalls then slowly backs up, some moisture can spread westward later in the weekend.