Quick April Storm


Bermuda Weather Service Radar 1:13am April 24th 2014. A bow echo feature organized out of isolated showers and thunderstorms ahead of a cold front, then cross the central and eastern part of the island bringing gale force gusts.
Bermuda Weather Service Radar 1:13am April 24th 2014. A bow echo feature organized out of isolated showers and thunderstorms ahead of a cold front, then cross the central and eastern part of the island bringing gale force gusts.

A cold front passed just after mid-night in the morning on the 24th. Isolated showers ahead of the front organized a bit just before crossing the island. They brought squally conditions with downpours, gale force gusts, and thunder. Much of the stronger winds were isolated to the central and eastern parishes of Bermuda where an initial squall line passed, but heavy rain and thunder was more widespread as the second line of showers crossed the island more entirely. The winds at the airport gusted to 38kts (44mph) with the passage of the squall line. Similarly, winds at my PWS in Devonshire gusted to 40mph. About a half inch of rain fell fairly quickly in association with these showers and thunderstorms.

The main low pressure associated with this cold front was far to the north of Bermuda, south of Nova Scotia, and strengthened as it traveled eastward along the Gulf Stream. As it did so, an area of gales in the cold air behind the cold front that passed Bermuda expanded, just about reaching the islands for the day on the 24th. Winds at the airport peaked sustained at 33kts (38mph) with a maximum gust of 45kts (52mph). Gales start when sustained winds reach 34kts.

GOES Image of the northwest Atlantic at April 25th 2014. This shows the parent low pressure centered to the south of
GOES RGB enhanced vis-ir Image of the northwest Atlantic at 4:45pm April 25th 2014 local time. This shows the parent low pressure associated with the 24th’s cold front centered to the south of Newfoundland. An approaching cold front can also be seen in the Eastern United States.

Although this front was fairly vigorous, producing notable thunderstorms, and an area of gale into the sub-tropics in April, the temperature only dropped off to near normal levels. The high on the 23rd, ahead of the front was an above normal 75.9F, but that only dropped to 70.5F on the 24th, in the ‘cold’ air behind the front. The big change in the airmass was the amount of moisture in the air, dew point temperatures ahead of the front (on the 23rd) were fairly steady at 62-64F, but were much lower on the 24th at 47-52F.

As a side note Northwest Atlantic sea surface temperatures are significantly above normal for this time of year. Sea surface temperatures measured by the Bermuda Weather Service were 73.1F on the 23rd, more than 5F above normal compared to the average April sea-surface temperature.

Bermuda is in the northwesterly flow between a weak ridge of high pressure to the west and strong low pressure to the northeast, temperatures have changed little between the 24th and 25th (highs around 70F) with continued pleasant humidity.

The ridge of high pressure to our west shifts eastwards, in response, our winds back more westerly, continuing to diminish, on Saturday with continued fair weather and near normal temperatures. The influence of that ridge is short lived as a cold front, currently over the eastern United States, will start to approach Bermuda Saturday night. In response, winds back to the southwest and begin to increase. Showers associated with that cold front are then introduced overnight Saturday into Sunday, largely clearing out before sunrise. Slightly cooler weather should be in place for Sunday. A post-frontal trough or secondary cold front then develops to the northwest of Bermuda, potentially introducing further showers to Bermuda for overnight Sunday into Monday (again largely ending before sunrise).

The parent low pressure associated with Sunday morning’s and then Monday morning’s cold fronts should then be south of Nova Scotia on Tuesday, slowly moving eastward then southeastwards. This keeps Bermuda in persistent moderate to strong northwesterly to northeasterly flow between the slow moving low pressure to the northeast and a cell of high pressure to the northwest, over New England. This pattern could persist Monday through to Friday. Cool air filtering in on this flow may allow for some light showers, but simultaneously, high pressure extending a ridge southeastwards from New England should act to generally suppress shower activity. Further, while at the start of the week, temperatures might be a little below normal, they should moderate back to normal despite the continued cool flow. It is fairly interesting to note that a similarly persistent pattern was in place to start April, and this bought may last until through to the end of April, potentially ending the month as significantly drier than normal.

Keep up to date with the latest official forecasts from the Bermuda Weather Service.

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