[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 011450
TCDAT2

Tropical Storm Larry Discussion Number   4
NWS National Hurricane Center Miami FL       AL122021
200 PM CVT Wed Sep 01 2021

Satellite imagery this morning shows that Larry is becoming better
organized, with curved convective bands increasing around the
center.  Various subjective and objective satellite intensity
estimates were in the 35-55 kt range around 12Z, and ASCAT data
near the time showed 40 kt winds.  Based on increasing organization
since that time, the initial intensity is increased to 45 kt.

Larry is moving quickly westward, although there is some uncertainty
in the forward speed due to the possibility the center re-formed
during the night.  The best estimate of the motion is 270/19 kt.  As
noted in the previous advisory, the cyclone is expected to move
around the southern and southwestern periphery of the sprawling
Bermuda-Azores ridge for the next 5 days, resulting in a general
west motion for 24-36 h, followed by a turn toward the
west-northwest and, by 96-120 h, a turn toward the northwest.  After
36 h, there is some spread in the track guidance, with the GFS
generally on the right side of the guidance envelope and the UKMET
on the left side, a spread often seen for westward-moving cyclones
south of the Bermuda-Azores high.  Due to a more westerly initial
position, the guidance has shifted a little more to the west, and
the new forecast track is again shifted to the west of the previous
track.  The new forecast lies a little to the south of the various
consensus models.

Conditions appear favorable for steady to rapid strengthening during
the next 48-60 h due to light shear, a moist environment, and sea
surface temperatures of 27-28C along the forecast track.  The new
intensity forecast calls for Larry to become a hurricane in about 24
h and a major hurricane near 60 h.  After that time, the global
models suggest the possibility of dry air entrainment, and by 120 h
there is likely to be moderate westerly shear over the cyclone.
Based on this forecast environment and the guidance trends, the
intensity forecast calls for little change in strength from 72-120
h.  The new intensity forecast lies near the upper edge of the
intensity guidance.


FORECAST POSITIONS AND MAX WINDS

INIT  01/1500Z 12.3N  27.6W   45 KT  50 MPH
 12H  02/0000Z 12.4N  30.4W   55 KT  65 MPH
 24H  02/1200Z 12.7N  33.4W   65 KT  75 MPH
 36H  03/0000Z 13.2N  36.5W   75 KT  85 MPH
 48H  03/1200Z 13.9N  39.2W   90 KT 105 MPH
 60H  04/0000Z 15.0N  41.9W  100 KT 115 MPH
 72H  04/1200Z 16.2N  44.6W  105 KT 120 MPH
 96H  05/1200Z 19.0N  49.5W  105 KT 120 MPH
120H  06/1200Z 22.0N  52.5W  105 KT 120 MPH

$$
Forecaster Beven
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