Daily Archives: Sunday, September 22, 2024 5:34 pm

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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This week’s weather will be influenced by low pressure (1) moving in from the west, a developing strong hurricane (2) in the Gulf, blocking persistent high pressure (4) to our north and persistent blocked low (3) in the Atlantic —

09-22-24 12z GFS for Tuesday afternoon Low pressure (1) moving in from the west, a developing strong hurricane (2) in the Gulf, blocking persistent high pressure (4) to our north and persistent blocked low (3) in the Atlantic (Click on image for larger view.)
Monday

Monday will be cloudy, perhaps with some sunny intervals around noontime.

The HRRR has some showers moving in late afternoon and early evening. How far they will get into the city is an unknown, since the HRRR has blocking high pressure building in at the same time—

09-22-24 18z HRRR with blocking high pressure (blue shading). This shunts much of the rain to our south. (Click on image for a larger view.)

The NAM-NEST is predicting most of these showers on Monday are shunted to our south, but some may give parts of our dry area some light showers.

We may finally get a period of rain on Wednesday, as the high pressure system will retreat to the northeast.

Towards the end of the week, the next hurricane (“Gordon”) is expected to form and to move inland around the Florida Panhandle or the Florida Great Bend area. according to the ECMWF AIFS. This hurricane could be powerful. Incredibly, our much needed rainfall here may be blocked by high pressure and an upper level ridge again.

There remains uncertainty about this possible hurricane, according to the National Hurricane Center and I may be jumping the gun on the hurricane forecast . Nonetheless, the GFS, ECMWF and CMC Global all predict some strong system.

Today’s 12z ECMWF AIFS forecast for Thursday at 8 PM. Hurricane Gordon is expected to form and to move northward from the Gulf. Much of the rain will move to our west and be blocked from our area. (Click on image for a larger view.)