The general computer model trend regarding the Thursday-Friday storm is to shift the axis of heavier precipitation a bit farther south. Right now, the NAM model is the most robust in keeping the heavy rain over interior SNE. Some other models, like the ECMWF and GFS have taken the heavy rain south to the Mid-Atlantic and Atlantic Ocean – which would be a welcome sight for waterlogged Southern New Englanders. The NOAA Weather Prediction Center has made big changes to their rainfall forecast. Earlier this morning the forecast was for nearly 5″ of rain in the hardest hit areas of Southern New England. The current forecast is for 0.75-1.5″ of rain for most of SNE, with the higher totals near the coast. I’m a little leery of the current forecast overcompensating for a one run shift in the models. The NAM, WSI RPM, JMA, and NAVGEM models all still have a multi-inch rain event for most of SNE. The GFS and European are great scenarios, with 0.5-1.25″ in RI and SE MA. That’s still a decent soaking, but would lead to far fewer problems than 2″+
The models that are drier have the storm diving east-southeast to the Mid-Atlantic coast then redeveloping off the coast and moving well southeast of Nantucket. As a result, the northern edge of the rain shield moves south of Providence and Boston for a while as the storm redevelops. Some rain is possible as it passes Nantucket on Friday. The NAM keeps the storm center much farther north, and that keeps the steady rain going over SNE.
As of 5 am, the Short Range Ensemble Forecast had a mean QPF (rainfall) of 2.5″ for Providence. That is 2-3x what the GFS, ECMWF are showing as of their 12z (8am) runs. The new SREF run available late Wednesday afternoon had a mean QPF of about 1.5″ for the Providence area. That’s a good sign.
