Tue 08:41 AM Update — graphics added below

The 2 AM (06UTC) runs of the models show the following changes in the forecast for tropical storm Isaias—

  • The storm is moving faster than previously forecast-  peak winds and rain rate will reach us between 10 AM and 1 PM.
  • The track of the storm is a bit further westward.
  • Rain totals will be the highest to the west of Philadelphia, in Lancaster county.  Still an additional 2-4 inches to fall. The precipitation maps posted yesterday still hold.
  • Higher localized rain amounts in thunderstorms.
  • Wind gusts will peak about 11 AM and again at 1 PM.  Wind gusts around 60 mph possible in the Philadelphia area, higher in NJ.
  • Rain will be ending by 2-3 PM

Some differences exist with areas of max rainfall.

Below is the latest GFS model accumulated rain forecast (from 2 AM, which does not include the rain from last night prior to 2AM. )

GFS forecast accumulated Rain from 2 AM  onward (Click on image for a larger view.)


Here’s the very latest HRRR (High Resolution Rapid Refresh) hourly model from 7 AM —

HRRR accumulated Rainfall from 7 AM