[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 280236
TCDAT5

Tropical Storm Tammy Discussion Number  35
NWS National Hurricane Center Miami FL       AL202023
1100 PM AST Fri Oct 27 2023

Strong southwesterly shear is taking a toll on Tammy tonight. Its
limited convection is confined to the northeastern portion of its
circulation, which is partially exposed in proxy-visible satellite
images. This shear has resulted in the vortex becoming vertically
tilted, with the mid-level center displaced to the northeast of the
low-level center in recent AMSR2 passive microwave images. Based on
these structural changes and the decreasing satellite intensity
estimates from TAFB and UW-CIMSS, the initial intensity is lowered
to 50 kt.

The deep-layer shear is expected to persist over Tammy during the
next few days, which should result in weakening while the storm
moves over marginal SSTs. While the forecast track does bring the
center of Tammy over warmer waters by early next week, the much
drier and more convergent upper-level environment should make it
difficult for Tammy to sustain organized convection. In fact, GFS
and ECMWF model-simulated satellite data indicate Tammy could be
completely devoid of convection within the next 2-3 days. The
updated NHC forecast is lower than the previous one, following the
latest IVCN and HCCA aids. Post-tropical remnant low status is shown
in 72 h, although this could occur even sooner than forecast.

The long-term motion of Tammy is north-northwestward (335/4 kt), but
recent satellite images indicate the cyclone is now turning
northward as anticipated. A faster eastward to southeastward motion
is forecast over the weekend as Tammy moves around the northern and
eastern sides of a mid-level ridge. Then, the weakening cyclone is
forecast to slow down and turn southward on Monday as the ridge
becomes positioned to its west. No major changes were made to the
NHC track forecast, which still lies between the simple and
corrected consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT  28/0300Z 32.7N  61.3W   50 KT  60 MPH
 12H  28/1200Z 32.9N  60.3W   45 KT  50 MPH
 24H  29/0000Z 32.6N  57.9W   40 KT  45 MPH
 36H  29/1200Z 31.9N  55.0W   40 KT  45 MPH
 48H  30/0000Z 30.5N  52.7W   35 KT  40 MPH
 60H  30/1200Z 29.1N  51.6W   30 KT  35 MPH
 72H  31/0000Z 28.2N  51.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  01/0000Z 28.1N  52.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  02/0000Z...DISSIPATED

$$
Forecaster Reinhart
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