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Subtropical Storm Andrea Discussion Number 3

Wiki-Hurricanes Forecast Center

12:00 PM AST Tue Mar 21 2019

... CORRECTION ... ALL RECONNAISSANCE TASKING CANCELLED FOR ANDREA ...

Visible imagery from this morning depict Andrea as having continued subtropical character, with a field of thin low-topped cumuli bands surrounding the center of circulation. Andrea has been largely devoid of deep convection since the morning, and cirrus continues to spread over the system from the upper-low to the south. Given good agreement from both objective CIMSS-ADT and subjective Hebert-Poteat analysis, the intensity for Andrea this advisory has been lowered slightly to a possibly optimistic 35 kt. SSMIS passes at 0956z and 1213z suggested the strongest winds - at least 30 kt in the clear - were located 2-4 degrees east of the center, with the bands near the center possessing 25-30 kt winds within the low resolution context.

Cirrus cloud motions indicate that upper-level winds continue to flow perpendicular to parts of Andrea's wind field, though this has been lightening over the last few hours. As the upper-level low to Andrea's south slides gradually eastward, there is a brief window of favorability later today and tomorrow within the relatively low wind shear field of the upper-trough axis. With cold temperatures of -57F aloft caused by the trough, the thermodynamic parameters are currently supportive of some convective growth. Given the rather loose nature of the subtropical system, however, it is unlikely that this will result in significant strengthening if any, coupled with the marginal degree of favorability and short timeframe of opportunity. Slight weakening is forecast before the vortex is expected to be stretched by the front before eventual frontal absoption.

Andrea is tracking gradually north-northeastwards along the edge of the subtropical ridge to the east. The approach of a fonrtal system and trough are expected to enhance a northeasterly to easterly steering flow beginning tonight. The storm's forecast motion suggests a track near Bermuda around daybreak tomorrow, though impacts are expected to remain limited to light rain and some modestly gusty wnds.

FORECAST MAX WINDS

INIT 21/1500Z 35 KT 40 MPH

12H 22/0000Z 30 KT 35 MPH

24H 22/1200Z 30 KT 35 MPH

36H 23/0000Z...DISSIPATED/ABSORBED BY FRONT

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