forecast

Warming Ocean Water Despite Cooler Air; Coastal Flooding Expected

The combination of a changed wind and Supermoon will have a coastal impact

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The heat and humidity have left New England, but that doesn’t mean the weather is quiet! 

In fact, there will be some subtle but important features impacting New England weather in the days ahead, and much of this revolves around the ocean. 

First, a northeast wind is delivering entirely new air to New England Wednesday, with afternoon high temperatures in the 70s to near 80 degrees and dew point temperatures, the measure of the amount of moisture in the air, down from sultry 70s to a much more comfortable level in the lower to middle 60s. This more comfortable air should stick around, at least for the most part, through the majority of the exclusive First Alert 10-day forecast!

The most obvious result is the shift from deep summer heat to more seasonable temperatures, bringing an end to a record stretch: a record 26 consecutive days of 80 degree or warmer high temperatures, a record hot 31 day stretch and, so far this season, we’ve tied the record for most days at or above 98 degrees with five (tying 1911 and 1944). Yet, amid all the heat, eastern Massachusetts and New Hampshire seacoast residents have been asking since July Fourth- why has ocean water been so chilly?

We covered that earlier in the season, but it’s noteworthy again because it’s about to change. The majority of this season has featured a westerly wind, sweeping the milder skin of surface ocean water out to sea, where it’s been sitting over the Gulf of Maine. Now that the wind has shifted to blow from the northeast, that will allow some of this milder ocean water to return back toward the shoreline and as of Wednesday morning we’ve already seen the buoy in Cape Cod Bay record a 5 degree, 24-hour water temperature jump and this should be felt at our eastern beaches in the coming days. It's a bit ironic since the air temperature is dropping enough that pools and lakes will cool pretty quickly, instead. 

Another noteworthy point for our coasts is the third and final Supermoon of the year is coming at the end of this week, meaning tidal levels are high and minor coastal flooding is expected in typically vulnerable spots along New England’s shorelines at high tide Wednesday night, Thursday night and Friday night. Meanwhile, the massive change in air, though complete at ground level, is still ongoing in the sky, which is why lots of clouds will continue to blot out the sun in the coming days, though particularly the afternoons will feature splashes of sun. 

Wednesday morning showers tapered to only lingering sprinkles, but new showers are expected Thursday morning, especially in southeast Massachusetts, scattered Thursday afternoon and perhaps one or two showers Friday and Saturday between breaks of sun and clouds.

In fact, the next 10 days will feature a pattern that often will bring an elevated chance of showers as the jet stream – the fast river of air high in the sky – dips south from Canada into the Northeast U.S., providing frequent energetic disturbances and temperatures close to normal for this time of the year.

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