Wet Start to December Continues


2015-12-10-1900_SAT004
Bermuda Weather Service Radar and Satellite layered imagery showing generally light and steady rain over Bermuda with  a band of heavier showers to the west of the island. At 3:00pm 10 Dec 2015. Link.

An notably wet start to December has continued today thanks to an area of low pressure south-southwest of Bermuda. As of December 9th, the Bermuda Weather Service has measured 3.28″ of rain for the month-to-date. In the 1949-1999 climatology, December sees 4.50″ of rain on average.However, the wettest December had 11.73″ in 1960 – a long way to go before breaking a record there.

A shield of steady rain spread across the island overnight as the low approached and lifted a lingering stationary front towards the island as a warm front.

10 Dec 2015 1815 UTC Jet Streak Analysis.png
GOES-East RGB imagery at 18:15UTC 10 Dec 2015 at 18:15 UTC with annotations showing two jet streaks at 300mb (~9 km) interacting with the surface low marked as a red ‘L’. Link.

The surface low is set in an environment of favorable upper divergence between the left exit region and right entrance region of jet streaks in a fairly active subtropical jet. This positioning suggests that some further deepening of the low is possible as it approaches, then passes to the south of Bermuda early tonight. As it passes, expect easterly winds to back sharply, becoming northerly and increasing from moderate to strong – possibly briefly to near gale force. Steady rain is expected to continue until late tonight when the low clears away to the east. Heavier embedded showers are also possible, and rain totals for the day could exceed an inch.

[Jet streaks are locally stronger winds within the jet stream. The jet stream is a narrow region of strong winds typically >7 km above ground, near the top of the troposphere. The jet stream often separates cold air poleward and warm air equatorward.]

10 Dec 2015 1447UTC ASCAT METOPB
ASCAT METEOP-B pass 10 Dec 2015 at 14:47 UTC showing an area of >25 kt northerly winds (orange and red wind barbs) to the west of Bermuda. Link.

As always, follow the latest official forecast from the Bermuda Weather Service.

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