[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 131434
TCDAT4

Tropical Storm Melissa Discussion Number   9
NWS National Hurricane Center Miami FL       AL142019
1100 AM AST Sun Oct 13 2019

After an overnight convective hiatus, likely due to Melissa passing
over a narrow band of cold water, deep convection has increased near
the center and a curved band of broken convection has developed in
the eastern semicircle. A 12Z TAFB shear pattern satellite intensity
estimate resulted in 45 kt while the curved band pattern produced 35
kt. An average of these estimates yields 40 kt, which is close to
the most recent UW-CIMSS SATCON and ADT estimates of 44 kt and 43
kt, respectively. Therefore, the initial intensity remains at 40 kt.

Melissa is beginning to accelerate east-northeastward and the
initial motion estimate is now 075/15 kt. A further increase in
forward speed combined with an eastward motion is expected over the
next couple of days as Melissa moves around the northern periphery
of the deep-layer Bermuda-Azores high. By late Tuesday and
Wednesday, Melissa is forecast to turn toward the east-southeast as
a weakening extratropical low pressure system.  The new NHC track
forecast was nudged a little to the right of the previous advisory,
and lies near the middle of the tightly-packed consensus guidance
envelope.

The westerly wind shear across Melissa is currently around 20 kt and
the cyclone is moving over sub-25 degree C sea-surface temperatures
(SST). Water temperatures ahead of the cyclone are forecast to
decrease to 21-22 deg C within 12 hours, while the shear is expected
to increase to 25-30 kt. The combination of these two negative
factors will result in weakening by this evening, which will
continue throughout the remainder of the forecast period, with
Melissa becoming a post-tropical remnant by Monday and merging with
a frontal system or larger extratropical low by Wednesday. The new
official intensity forecast is similar to the previous advisory, and
closely follows a blend of the HCCA and IVCN intensity models.

FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 39.8N  60.9W   40 KT  45 MPH
 12H  14/0000Z 40.5N  57.7W   35 KT  40 MPH
 24H  14/1200Z 41.4N  53.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  15/0000Z 41.9N  47.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  15/1200Z 41.8N  41.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  16/1200Z...DISSIPATED

$$
Forecaster Stewart
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