NHC issues Tropical Cyclone Discussion (TCD) at Oct 11, 7:00 PM AST431
WTNT43 KNHC 111448
TCDAT3
Tropical Storm Leslie Discussion Number 37
NWS National Hurricane Center Miami FL AL132024
1100 AM AST Fri Oct 11 2024
Leslie remains a sheared tropical storm. The low-level center is
exposed about 70 n mi outside of the northern edge of the convective
area, which has been shrinking and weakening over the past several
hours. As a result, subjective Dvorak estimates from TAFB and SAB
are both down to 45 kt. A pair of recently arriving ASCAT passes
still show an area of 40-44 kt winds in the eastern semicircle. The
initial intensity is set to 45 kt, which agrees well with the
subjective Dvorak estimates and the ASCAT data.
Leslie is likely currently experiencing more than 30 kt of
north-northeasterly vertical wind shear. The cyclone will be moving
toward an upper-level ridge axis over the next 12 to 24 h, which
will cause the deep-layer shear to decrease. However, Leslie will
reach sea-surface temperatures colder than 26C in about 24 h, and it
is forecast to remain in a relatively dry low- to mid-level
troposphere. Some slight additional weakening is forecast today,
followed by little change in strength for the next couple of days.
The intensity forecast is near the middle of the intensity model
guidance envelope. The GFS and ECMWF simulated satellite imagery
agree that the cyclone will lose its convection by 48 h, but
phase-space diagrams suggest that Leslie could potentially become
extratropical before that time, by 36 h. The NHC forecast continues
to show Leslie becoming post-tropical over the weekend, in agreement
with the aforementioned guidance. Leslie is still expected to
dissipate by day 4, as shown by the global models.
Leslie has been moving toward the north-northeast, or 015/9 kt, as
the cyclone rounds the western periphery of a subtropical ridge. A
strong frontal trough will approach Leslie from the west tonight
into Saturday, causing Leslie to accelerate toward the northeast.
Leslie's interaction with this frontal system could cause the
cyclone to lose its tropical characteristics by Saturday night. On
Sunday, the cyclone is expected to turn more towards the east within
the mid-latitude westerly flow. No significant changes were made to
the first 48 h of the official track forecast, with a slight
southward adjustment at the 72 h point. The NHC track forecast is
very near the TVCA consensus.
FORECAST POSITIONS AND MAX WINDS
INIT 11/1500Z 26.4N 50.5W 45 KT 50 MPH
12H 12/0000Z 28.4N 48.9W 40 KT 45 MPH
24H 12/1200Z 31.7N 45.1W 40 KT 45 MPH
36H 13/0000Z 34.6N 39.9W 40 KT 45 MPH...POST-TROPICAL
48H 13/1200Z 36.2N 34.4W 40 KT 45 MPH...POST-TROPICAL
60H 14/0000Z 36.8N 29.3W 35 KT 40 MPH...POST-TROPICAL
72H 14/1200Z 36.4N 24.6W 30 KT 35 MPH...POST-TROPICAL
96H 15/1200Z...DISSIPATED
$$
Forecaster Hagen
Source:
NHC issues Tropical Cyclone Discussion (TCD) at Oct 11, 7:00 PM AST---------------
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