The remnants of Hurricane Ida will pass through Southern New England tonight and first thing Thursday morning. While the system is far from the catastrophic hurricane that impacted Louisiana, it still packs a punch and will deliver some dangerous weather to the Mid-Atlantic, Northeast and New England today, tonight and first thing Thursday.
Far and away the biggest threat from Ida’s remnants will be extremely heavy rainfall over a large portion of the Northeast. Parts of Pennsylvania, New York and into central and western New England are preparing for widespread 4 to 6 inches of rain with spot totals of 6 to 8 inches. In fact, the folks at the National Weather Service’s Weather Prediction Center have placed a large geographic region under a “High Risk” for excessive rainfall and potentially life-threatening flooding. Certainly a rare occurrence and one that needs to be monitored.
Here on the Cape, we should be spared the extreme rainfall but we too will see our share of downpours, with a solid 1 to 2 inches of rain a good bet from east to west across the area (highest totals near the Canal, lower totals out on the Lower Cape).
The Cape is the only location in Southern New England that actually NEEDS the rain. The Lower Cape is in a Severe Drought per the U.S. Drought Monitor as very little precipitation has fallen in recent months (dating back to last summer). So whatever falls locally is actually rather welcomed. Over inland locations, what has turned into one of the wettest summers on record is setting the stage for potentially devastating flooding.
While we don’t have to worry too much about a serious flood event in our area (though some localized street flooding could occur with any heavy downpours that train over the same spot) we do have two additional hazards to monitor: gusty winds and an isolated tornado threat.
The circulation of Ida still has plenty of shear (winds changing direction and speed with height) along with it and most model guidance agrees that extreme Southeastern New England will be grazed by the system’s warm sector late tonight and early Thursday morning. Consequently, there will be just enough instability around to yield downpours and thunderstorms accompanied by strong low level rotation. Obviously tornadoes and waterspouts are not a common occurrence in these parts, and thus we wouldn’t EXPECT a tornado to happen, but the threat is unusually high for this region. The window of time to pay attention to most closely seems to be about 3AM to 8AM or so.
In addition to the severe weather threat, we’ll have to deal with some strong winds – initially from the south first thing Thursday morning and then again from the north during the midday and afternoon hours. A rather strong low level jet crosses the region and will be accompanied by a notable pressure fall and rise (by summer standards). Multiple pieces of guidance show wind gusts in excess of 40 mph across our area…with the Outer Cape potentially going higher than that. This will need to be watched as the combination of fully-leafed trees and downpours will make it easier to take down some limbs and trees.