A very unsettled end to August


Tropical Rainfall Measuring Mission (TRMM) Satellite Derived daily precipitation anomaly in mm/day. Bermuda's location is highlighted in red.
Tropical Rainfall Measuring Mission (TRMM) Satellite Derived daily precipitation anomaly in mm/day over the last 30 days. Bermuda’s location is highlighted in red. Satellite indicates that, for August, Bermuda saw about 5mm/day of rain more than normal. 

A slow moving frontal system interacted with several troughs in the western Atlantic near Bermuda to bring days of heavy showery rain and thunderstorms to end August. These were even squally at times with gusts as high as 40kts observed at the Bermuda Weather Service. August 2013 has ended as significantly above normal for precipitation with 10.43″ recorded at the Bermuda Weather Service; a full 4″ above normal for the month as compared to 1981-2010 climatology of 6.38″. This month’s surplus completely eradicated the year-to-date precipitation deficit. There were three days that each saw more than an inch of rain, that statistic combined with a near normal number of precipitation days indicates that when it did rain, a lot of rain fell at once. Interestingly, these thunderstorms came with significant cloud to ground lightning that was blamed for power outages on two separate occasions when utility poles were struck.

A result of the heavy showers was several record and near record low temperatures as the heavy rain cooled the air. The daily record low temperatures of 70.9°F on the 15th and 69.4°F on the 26th were found only in heavy showers and thunderstorms. And overall, temperatures were kept around 2°F below normal for August – likely with some relation to the unsettled weather. It is not unusual for a front to make it near Bermuda and then stall and dissipate or lift out of the area during August – but it is a bit unusual for several fronts to pass through Bermuda in August bringing a change in airmass. This is likely related to the Bermuda-Azores high averaging nearer the Azores than normal.

For official climate data, see it as provided by the Bermuda Weather Service here.

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