Morgan’s Cloud Looms


Close up of Bermuda as seen on Bermuda Weather Service radar at around 3:36pm local time. Morgan's cloud associated showers extending northeast of the island.
Close up of Bermuda as seen on Bermuda Weather Service radar at around 3:36pm local time. Morgan’s cloud associated showers extending northeast of the island.

Mid-late June heat and humidity in a tropical air mass, combined with a light southwesterly breeze allowed clouds to thicken over the east end of the island yesterday. This is a local phenomenon known as Morgan’s Cloud (see the Bermuda Weather Service Glossary for this and other local weather terms). When light winds blow the length of the island (southwest or northeast) this allows for maximum heating of the low levels making an otherwise stable weather pattern much more unstable, allowing for convective cloud development. In the late summer months, when tropical airmasses can become deep and well entrenched in the area, this can produce thunderstorms usually off the east end of the island, some of which can produce significant weather.

One of the several funnel clouds that were spotted yesterday afternoon and evening in and around St. George's and St. David's.
One of the several funnel clouds that were spotted yesterday afternoon and evening in and around St. George’s and St. David’s.

Yesterday, wind conditions became very favorable for Morgan’s Cloud development despite the air not being as tropical as is typically necessary, and moderate showers hung over the east end and extended northeastward into the marine area. These produced several funnel clouds in and around St. Georges – fortunately, no damage was reported, but they were a sight to see. Funnel clouds aren’t uncommon in Morgan’s cloud because these conditions are the same that are favorable for waterspout development.

Variable winds and warm humid weather will continue as a frontal system stalls and breaks up to the north of Bermuda, keeping the island under the axis of a ridge extending from the Bermuda-Azores high. Further isolated showers are possible through the next few days, developing from the heat of the day across the island and popping up over the island. With winds so light, these showers could sit in place and dump a quick 0.50-1.00inch of rain before fizzing up bringing a return to summer-like heat. Some showers may return before sunset, but generally clear out at night as the land cools off.

As an ending note, Tropical Storm Barry moved inland into Mexico with 45mph winds yesterday and has since degenerated into a remnant low that is still producing some unsettled weather and threatening flooding in Mexico. There is a segment of a stationary front off the coast of South Carolina that may try to develop, but the chances of that seem slim at this point. Otherwise, the Atlantic has returned to a more seasonable quiet.

Stay tuned to the Bermuda Weather Service for the official forecast, observations, and tropical products (tropical products can also be found at the National Hurricane Center website).

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