Wet and Windy Weather Weekend


Sep 28 15 1345 UTC RGB Annotated
Satellite image showing the easterly surface flow with moist southerly mid level flow over running it with connections to tropical depression 11. The stationary front to the south is serving as a focus point for the convection.
Skew T 2015092812Z Analysis
Another view of the two layered flow can be seen in this morning’s skew-t diagram for Bermuda. Low level easterly flow (surface to 4000m) with southerly through southwesterly mid level flow just above it. This is a very moist airmass through the entire column – a measure of that is the precipitable water (PWAT) which is highlighted in green as 50.81mm.

Saturday evening saw a slow moving cold front slide southwards across Bermuda. The front brought gusty showers and downpours as it crossed the island and, as it became stationary to the near south of the island, ushered in near gale force easterly winds with gale force gusts and significant rains.

Rain and shower activity continue today as deep tropical moisture flows around both the remnants of tropical storm Ida to the distant southwest and newly formed tropical depression 11 to the distant southeast. TD11 is expected to both remain weak and not have direct impacts on Bermuda. This moist flow is then lifted by the stationary front to the near south of the island, serving as a focus for shower activity to form and spread northward across the island. Significant rainfall totals from this long duration event are expected, with some areas already seeing over 2″ of rain since Saturday night, and an additional 1-4″ of rain possible as the stationary front lifts northward through Wednesday.

A strong pressure gradient (between the high pressure to the north of Bermuda and the two tropical systems to the south) behind the front is responsible for the continued near gale force easterly surface flow in Bermuda. Locations at elevation with easterly exposure have seen frequent gusts over gale force and sustained winds to gale force at times. A Gale Warning is in effect for sustained winds at elevation and in the marine area reaching gale force (>34kts, 39mph) at times today.

Expect near gale/gale force easterly winds to slowly veer southeasterly and decrease from near gale force to strong tonight. Winds continue settle out of the southeast on Tuesday and remain moderate to strong through the rest of the work week.

For the latest official forecast see the Bermuda Weather Service. For the latest official information on TD 11, see the National Hurricane Center, and the Bermuda Weather Service’s Tropicals Page.

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