Weather And The Bay: Part III

Weather And The Bay: Part III

The Bay, Fog, Precipitation & Thunderstorms

As we saw last week, Narragansett Bay can have a major affect on air temperatures and thus directly play a part in how you feel on, say, a hot, steamy summer day or at other times of the year. The Bay can also directly affect weather systems large and small by either modifying or enhancing weather phenomena such as precipitation, fog, clouds and thunderstorms.

Let’s take the case of clouds and fog (fog merely being a cloud that has formed or is sitting on the ground). As moist air cools it can reach a point where it becomes saturated or, put in another way, reaches 100% relative humidity. Water vapor in the air (an invisible gas) then condenses into tiny suspended water droplets that make up the cloud (or fog). If the cloud droplets become large enough they fall from the clouds creating what we know as precipitation. This happens most often high in the atmosphere, but can also take place close to the earth’s surface, and if it is right on the ground or water surface the cloud formed is called fog. In the cooler months of the year, the water of Narragansett Bay is chilly and often much cooler than the moist air passing over it. The water will then cool the air to the point of saturation forming fog banks and at times drizzle and light rain. As I mentioned, this happens most frequently in the cooler months and less often in the summer when the Bay waters are much warmer. If the air is dry to start with and moving quickly on gusty winds, then fog rarely has a chance to form.

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The Bay also can affect winter storms in a major way, particularly in the early part of the winter. The somewhat “milder” maritime air often changes snow to rain near and along coastal areas. It is common to see 12” snow amounts in Smithfield dwindle to a couple of slushy inches in Providence and to bare, wet roads in Narragansett and Newport. All due to the moderating affect that the Bay water has on the atmosphere.

Interacting with the Bay also can change the intensity of thunderstorms. During the spring and summer strong, gusty storms that feed on warm, soupy air at times form in Connecticut and Western Rhode Island and then move from west to east across Rhode Island, eventually encountering Narragansett Bay. Many times, but not always, the cooling and thus stabilizing affect of that maritime air can knock the stuffing out of the heavy storms as they move into communities surrounding the Bay. A very violent storm in Coventry may end up being a much tamer shower with a few lightning flashes and the rumble of thunder by the time it reaches Barrington. One caveat. If a strong cold front moving across the area causes the strong thunderstorms, the Bay usually has little or no influence on the intensity of the storms.

Next week: Part IV: Reversal: How Our Weather Affects The Bay