David Epstein: Here’s how Tropical Storm Isaias will affect New England

Isaias is forecast to bring rainfall and winds to the region beginning Tuesday night.

Joe Raedle
A wave crashes ashore in Fort Pierce on Florida's east coast as Tropical Storm Isaias passes through on Sunday.

Tropical Storm Isaias briefly became a hurricane before coming onshore in North Carolina on Monday night and now is moving through Virginia. It will rapidly pass right around Philadelphia before moving west of New York City and then on up into Vermont on Tuesday evening before ending up northeast of Montreal in the wee hours of Wednesday morning.

Tropical Storm Isaias will move into Canada early Wednesday morning.

This is a far western track for an impact here in New England. Tropical systems lose their strength when they move over land, so winds will be diminishing around the center. However, as storms become more extratropical, whatever wind field is left tends to expand. This is why although we are far from the center of the storm, there could be some stronger gusts this evening. There is a tropical storm warning posted, but many areas may not reach that strength, which requires sustained winds of 39 miles per hour.

There is a less than a 50 percent chance Boston sees tropical storm force winds Tuesday.
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Nearly all of the rainfall will miss central and eastern portions of the area, with heavy rain out toward the Berkshires. There will be a little finger of precipitation moving north Tuesday afternoon and evening with some embedded thunderstorms. Between 4 and 8 p.m., this area will move from the southwest suburbs to the northeast and up into Maine. For the Boston region, this is the timeframe when you can expect any rain or severe conditions. There will be isolated showers outside of this window, but that’s the core of the storm.

The dry weather this summer will now become even more exacerbated without any significant relief from rainfall. Although rain from this storm will be scattered, it’s not impossible that some of these thunderstorms contain a brief, weak spin-up tornado, but it is very unlikely.

The Storm Prediction Center, which is part of the NOAA, has outlined an area of possible tornadoes Tuesday. This area could expand north later in the day.

In terms of any coastal issues, the lack of close proximity to our coastline means no significant issues at the time of high tide. Boaters and other water enthusiasts should be aware of the possibility of thunderstorms later this afternoon.

The system is moving very quickly, and, by Wednesday morning, it will be partly sunny. An isolated shower is possible during the day Wednesday, but, again, this is the exception and not the rule.

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As a matter of fact, if you’re on vacation this week, the weather Wednesday and Thursday looks really nice. The nice weather may continue into the weekend, but we do have one issue: There’s going to be a weather system to the south of New England, and some moisture may try to sneak up from the south Friday night and Saturday. If you have plans to be on Cape Cod, Saturday could be cloudy and even showery. This part of the forecast will need to be refined later this week.

Temperatures will start to approach 90 degrees early next week along with an increase in humidity. Summer still has a lot of gas left in the tank.

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