We have a nice cool start in New England, but all eyes are looking south.
Dorian continues to generate historic rainfall, hurricane winds and storm surge, and dozens of tornadoes in North Carolina overnight. Outer rain bands of Dorian may arrive in southern New England by sunset today.
This morning we have a frost advisory in Northern Maine, and a tropical storm watch in southern Maine for tonight, a rather unusual combination.
Cape Cod and the Islands have a tropical storm warning for Friday night and Saturday.
Our Friday features mostly cloudy skies south and partly sunny north, with high temperatures in the 60s to low 70s. Wind from the east increasing to 10 to 20 miles an hour in southern New England.
It’s a tricky forecast tonight as Hurricane Dorian will transition from a tight warm core storm into an expansive, post-tropical storm overnight into Saturday morning.
What that means is instead of being a warm core storm with a tight circulation, it becomes a cold core system and expands rapidly with its rain and wind bands hundreds of miles from the low pressure center. Timing that transition and placing the outer bands is on the forefront of cutting edge meteorological ability.
In other words, it’s a huge forecast challenge. And the forecast is only of moderate confidence for Friday night and Saturday morning.
What we do know is that western to northern New England are going to feel little to no impact from Dorian, which will pass 140 miles southeast of Nantucket around sunrise Saturday.
We also believe the highest impact should be right along the immediate coast from Block Island, to Nantucket, to Downeast Maine. In these coastal areas we’re going to have ocean swells up 10 to 15 feet with possible wind gusts past 50 mph, creating minor coastal flooding and moderate coastal erosion.
These locations are also most vulnerable to heavy rain— we may see rainfall amounts of 1 to 3 inches.
A lot depends on how fast Dorian transitions from a hurricane into a pure cold core nor’easter.
You can tell by stepping outside Friday night and early Saturday, we are in chilly air, which is not ripe for a pure tropical storm. So when the rain does come in it’s going be a cold rain, and we may end up having to turn the heat on in spots where temperatures dip into the 50s. That rain will also possibly be heavy with wind gusts to tropical storm force, 40-plus mph.
Post-tropical storm Dorian will then race away Saturday afternoon with clearing from west to east. High temperature in the 50s where it stays wet much of the day. In western New England, we should get a good amount of sunshine, with temperatures in the 60s and 70s, and wind is not a factor.
An additional front comes in with a chance of a shower in far northern and western New England both Saturday afternoon and Sunday. But with a brighter sky Sunday, we should be able to get to 70 degrees in parts of southern and eastern New England, even as a cooler air mass moves in from the west and north later Sunday and Sunday night.
It looks like the New England Patriots will play under a bright moon with temperatures falling through the 60s into the 50s. Stay tuned to latest developments in our First Alert 10-Day Forecast.