5AM AST discussion
Posted by
cypresstx on 1/15/2016, 7:51 am
said extra-tropical transition was likely beginning, completed within 12 hrs
Tropical Discussion #7
WTNT41 KNHC 150846
TCDAT1
HURRICANE ALEX DISCUSSION NUMBER 7...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL AL012016
500 AM AST FRI JAN 15 2016
Corrected 48-hr forecast position
The overall convective pattern of Alex has continued to erode since
the previous advisory. However, conventional and microwave satellite
imagery indicate that there is still enough inner-core convection
and a small radius of maximum winds to warrant keeping Alex as a
hurricane for this advisory. Satellite classifications continue to
decrease, and the initial intensity has been lowered to 65 kt based
on a blend of the TAFB current intensity estimate of T4.5/77 kt and
a current T-number of T3.5/55 kt.
Alex has yet to make the turn toward due north, and the initial
motion estimate is 005/20 kt. Other than to nudge the forecast track
slightly to the right based on the more eastward initial position,
there are no significant changes to the previous forecast track or
reasoning. Alex is expected to be steered northward and then
northwestward over the next couple of days within deep cyclonic flow
in the eastern periphery of a large extratropical low centered over
the northwestern Atlantic near Newfoundland. On the forecast track,
the center of Alex and the core of strongest winds should reach the
central Azores by late morning or early afternoon. The global and
regional model guidance remains in excellent agreement on this
scenario, and the official forecast track is a blend of the
consensus model TVCN and input from the Ocean Prediction Center.
Most of the coldest cloud shield has now shifted into the western
semicircle, a signal that extratropical transition is likely
beginning. With Alex now moving over 16C sea-surface temperatures,
and with colder water still ahead of the cyclone, transition to
an extratropical cyclone should be complete within the next 12
hours. However, global models suggest that there will be enough
baroclinic forcing to maintain hurricane-force winds after
transition occurs despite the cold waters of the north Atlantic.
The 34-kt wind radius was expanded in the northeastern quadrant
based on quality wind reports from ship BATFR17. The wind field is
expected to continue to expand as Alex undergoes extratropical
transition at higher latitudes. The wind radii forecasts are based
primarily on guidance from the NOAA Ocean Prediction Center.
FORECAST POSITIONS AND MAX WINDS
INIT 15/0900Z 36.8N 27.0W 65 KT 75 MPH
12H 15/1800Z 41.4N 27.7W 65 KT 75 MPH...POST-TROP/EXTRATROP
24H 16/0600Z 48.7N 30.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
36H 16/1800Z 56.0N 34.5W 65 KT 75 MPH...POST-TROP/EXTRATROP
48H 17/0600Z 56.5N 47.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
72H 18/0600Z...ABSORBED BY EXTRATROPICAL LOW
$$
Forecaster Stewart |
128
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