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Subtropical Storm ALEX Forecast Discussion Number 1
2016-01-13 21:32:31| National Hurricane Center (Atlantic)
Issued at 500 PM AST WED JAN 13 2016 000 WTNT41 KNHC 132032 TCDAT1 SUBTROPICAL STORM ALEX DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012016 500 PM AST WED JAN 13 2016 Curved bands of cloudiness and showers/thunderstorms associated with the low pressure system over the eastern subtropical Atlantic have become better defined over the past 24 hours. Although the convection is not very deep, it is likely of at least moderate intensity given the relatively shallow tropospause over the area. Given the increased organization, and the apparent dissipation of nearby frontal features, advisories are being initiated at this time. The cyclone is co-located with an upper-level low, and appears to have only a weak warm core, so it is being designated as a subtropical storm. The current intensity is set to 45 kt in agreement with an earlier scatterometer overpass. A ship traversed the northern portion of the circulation earlier today and did not observe winds of tropical storm force and this is reflected in the advisory wind radii. The cyclone has been turning toward the left as it moves in the flow on the east side of a shortwave trough, and the initial motion is northeastward or 055/12 kt. The trough is expected to continue to swing counterclockwise around a broader mid-latitude cyclonic gyre, and this should result in Alex turning northward and north-northwestward over the next several days. The official forecast track follows the dynamical model consensus. Although the shear is not forecast to become very strong over the next several days, the cyclone will be moving over progressively colder waters. Therefore no increase in strength is shown for the next day or so. In the latter part of the forecast period, some strengthening is possible due to baroclinic processes. By 96 hours, the global models show the cyclone merging or becoming absorbed by another extratropical low at high latitudes. Alex is expected to become an extratropical cyclone by the time it passes near or over the Azores, so no tropical storm warnings are being issued for those islands. However, gale force winds are likely to affect portions of the Azores beginning late on Thursday or early on Friday. Alex is the first tropical or subtropical storm to form in January since an unnamed system did so in 1978, and is only the fourth known to form in this month in the historical record that begins in 1851. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 27.1N 30.8W 45 KT 50 MPH 12H 14/0600Z 28.9N 29.7W 45 KT 50 MPH 24H 14/1800Z 32.0N 28.2W 45 KT 50 MPH 36H 15/0600Z 36.3N 27.5W 45 KT 50 MPH 48H 15/1800Z 42.3N 28.2W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 16/1800Z 56.0N 34.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 17/1800Z...ABSORBED $$ Forecaster Pasch
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