Unsettled Weather


A stationary front oriented west-east to the north of Bermuda has allowed persistent southerly to southwesterly flow. A wave of low pressure then developed along the stationary front and tracked eastward. This enhanced the warm humid southerly flow as it locally drew the stationary front further northward – away from Bermuda as a warm front. A tropical low that moved east off the Florida coast elongated into a trough and produced intermittent deep convection as it became a pre-frontal trough Sunday evening. This convection waned into Monday morning, but collapsing thunderstorms created a surface outflow boundary and gust front. Late monday morning, this gust front was entering the Bermuda Marine area where the lower atmosphere was slightly less stable. Isolated showers began to develop ahead of the gust front, and convection was enhanced along it briefly as it crossed the island.

Bermuda Weather Service Radar at 11:06am as the enhanced segment of the gust front was crossing the island. An isolated shower, enhance by island heating can be seen to the northeast of the island.
Bermuda Weather Service Radar at 11:06am as the enhanced segment of the gust front was crossing the island. An isolated shower, enhanced earlier by island heating can be seen to the northeast of the island.

The core of strongest winds associated with the segment of the gust front that crossed Bermuda on Monday brushed north shore and crossed through Hamilton and St. George’s parishes. Gusts reached 35kts at the airport and 42kts at St. David’s lighthouse. Elsewhere gusts were <30kts but it is possible that there were storm force gusts over the northern marine area. These gusts were associated with moderate to locally heavy rain and a wind shift from southerly to a more westerly direction. Reports around the island show 0.12-0.33″, the higher amounts were due to isolated pre-gust front showers.

The gust front was then followed by patchy light rain. The pool of cold air behind the gust front from the initial collapsing thunderstorms and this patchy light rain kept afternoon temperatures in the upper 70s instead of the mid 80s.

The gust front dissipated to the south of the island Monday evening. Further convection along the cold front advancing from the northwest, associated with the same wave of low pressure along a previously stationary front, moved into the area. These developed into thunderstorms that produced heavy rain at times in the predawn hours on Tuesday. The cold front became stationary, draped west-east across the island. Isolated showers developed along the front Tuesday evening and overnight into Wednesday morning, adding to the rainfall totals. Storm totals from Tuesday and Wednesday were widespread 1.00-1.50″. The Bermuda Weather Service office saw 1.08″ in that two-day period. This was much needed rain as the island had been in a dry spell following a drier than normal April, May and early June – typically the driest time of year to begin with.

Wednesday afternoon, Thursday and Friday saw a return to humid southerly and southwesterly flow as the stationary front retreated northward and a ridge associated with the Bermuda-Azores high strengthened to our south. Decreasing stability in this humid flow allowed isolated showers each day, and a Morgan’s cloud did develop to the northeast of the island – this resulted in a persistent shower just northeast of Bermuda.

 

 

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