A reminder! This is Insights, our in-depth meteorological analysis – for a quick, 24-hour overview, check out Noyes’ Notes/1°Outside Today! The National Hurricane Center’s “Cone of Probability” for the track of Tropical Storm Debby comes right over New England this weekend. Matt Noyes says it’s unlikely to bring tropical storm force winds to New England, but some gusts to tropical storm strength are possible – the bigger culprit will be rain. Not only does Debby’s remnant bring rain, but northern jet stream disturbances ahead of it bring rain of their own in the next 36 hours that should cause at least isolated flash flooding for far Southern New England. Get the outlook through Sunday in this “deep dive” into New England meteorology.
In the past 24 hours, we’ve seen significant storms in parts of central New England, although significant rain amounts certainly haven’t been widespread. Today and tonight, we’re expecting more downpours with northern jet stream disturbances, followed by a brief break in the weather later tomorrow into Thursday.
Debby is moving slowly across the Southeast United States, dropping historic rainfall for similarly historic flooding along its path. As Debby moves, it will bring moisture into our region by Friday and Saturday, resulting in a period of heavy rain and some gusty South Coast and coastal water winds.
With abundant moisture in the atmosphere, showers and downpours will be significant this evening and tonight south of New England, but then will expand north during the night. Some areas, especially near the south coast of Connecticut, could see three to four inches of rain, leading to potential flooding overnight Tuesday night. Wednesday morning showers and downpours will kick southeast and most of New England should be much drier by afternoon, with dry air lasting through Thursday. By Friday, Debby’s remnant storm center moves toward New England, resulting in expanding and intensifying rain. All told, five day rain totals from Tuesday through Saturday will be three to five inches for Southern New England, with two or three inches in Northern New England. Not only will this be enough for pockets of flash flooding during heaviest rainfall rates (Tuesday night at the South Coast, then again Friday evening/night into Saturday AM for more of New England), but it should be enough for some river flooding by the weekend, as well.
As Debby transitions from a tropical depression to a non-tropical system, the wind will not be a significant factor by New England standards. That said, while tropical storm-force sustained winds (39 mph or greater) are unlikely, gusts to or over 39 mph are possible from the south Saturday predawn to Saturday late day, especially across the Cape, Islands, adjacent coastal waters and the Gulf of Maine.
Saturday will see continued rain and gusty winds due to Debby’s remnants. By Sunday, we expect better weather with a significant drop in humidity as Canadian air moves in. Dew points will drop to the 50s, bringing much more comfortable conditions into early next week.
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