Updated Wed 10:42 PM — Tonight’s NAM NEST model has generalized 4 inches of rain Friday, starting early morning and ending in the evening.
The coastal low expected to take on tropical characteristics and affect our area Friday has had an interesting history as far as the model predictions are concerned.
It was just a day ago that the much touted European model (ECMWF) and the GFS model were predicting it to just brush the coastline, missing us. Meanwhile the current track had been predicted by the NAM and SREF models, often wrong about such storms.
The new GFS, still under development and experimental, had picked up the current track sooner than the current operational GFS model. It suggests that weather forecast accuracy may improve when the new GFS is released in 2021.
It appears that the storm will affect us starting early Friday morning. About 1.5 -2 inches of rain will fall on Friday, with locally heavier amounts possible. Heaviest amounts just west of Philadelphia.
Updated Mon 01:39 PM — The storms developed around 1 PM, but not where predicted by the models. Also, the storm movement is different than predicted as well (or there’s something wrong with my data.) We’re getting some small size hail around here.
Live Radar at 12:56PM- Starting Thunderstorm development. (Click on image for a larger view.)
The models from last night and this morning show thunderstorms developing over central NJ near Bucks County about 1-3 PM today and moving from northeast to southwest! Some of these thunderstorms will have very heavy rain!
HRRR storm motion direction at 3 PM
Most areas near Philadelphia will have showers and thunderstorms, but some areas which have been dry over the past few weeks may again miss some of the heaviest rains.
(There’s a negative feedback loop where there are existing dry conditions. When soil moisture is low, it negatively affects the development of thunderstorms. Dry begets dry!)
