Subtropical Storm Ana Forms


The area of troughiness north of the Bahamas earlier this week has drifted northwards and organized a closed area of low pressure, cut off from fronts, and is sustaining organized deep convection. As a result of these structural changes in the low (confirmed via Air Force Hurricane Hunter missions,) the National Hurricane Center has determined that this low has become a Subtropical Storm.

Ana is expected to meander over the Gulf Stream, just offshore of the US east coast, for two to three more days before being picked up and taken northwestward into South or North Carolina by increasing southerly flow ahead of a mid-latitude weather system late in the weekend/early next week. This mid-latitude system is also expected to bring heavy snow to the Wyoming, Colorado, Nebraska and South Dakota – in addition to a “moderate” risk for severe thunderstorms (including hail, damaging winds and tornadoes) in the southern Great Plains as it pushes eastward.

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Counties highlighted blue for Winter Storm Watches from NWS at 10:45am local.
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Storm Prediction Center convective outlook for Friday showing a moderate risk for severe weather in red over Oklahoma and Texas.

Meanwhile, troughiness related to what were the fronts that Ana shed to become subtropical in addition to a cold front approaching from the northeast are bringing chances from showers and thunderstorms this afternoon through early Sunday morning. As a result, the Bermuda Weather Service has issued a Thunderstorm Advisory. The cold front doesn’t quite make it across Bermuda, dissipating on Saturday, so winds remain light to moderate and southeasterly through the beginning of next week thanks to Ana to the distant southwest this weekend and high pressure to the northeast behind that weak front early next week. While the cold front never really made it to Bermuda, slightly less humid air will still filter in on return flow from the southeast associated with that high pressure to the northeast of Bermuda early next week.

Subtropical Storm Ana circled in red, motion indicated by a red arrow. Troughiness near Bermuda circled with a dashed red line, and an approaching cold front highlighted with a blue line.
Subtropical Storm Ana circled in red, motion indicated by a red arrow. Troughiness near Bermuda circled with a dashed red line, and an approaching cold front highlighted with a blue line. Overtop RGB Satellite imagery at 10:45am local time.

For the latest on Ana see updates from the National Hurricane Center and the Bermuda Weather Service – Tropical Products. For the latest official forecasts including watches and warnings for Bermuda, also see the Bermuda Weather Service.

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