[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 200841
TCDAT1

Tropical Storm Peter Discussion Number   7
NWS National Hurricane Center Miami FL       AL162021
500 AM AST Mon Sep 20 2021

Peter is a strongly sheared tropical storm. Reconnaissance wind
data, conventional satellite imagery, and passive microwave
satellite data indicate that Rose's center is located just to the
west of the deep convection. Data from the aircraft support holding
the intensity at 45 kt for now based on 925-mb flight-level and SFMR
winds of 53 kt and 41 kt, respectively, on their last leg when the
aircraft came in from the northeast. The central pressure had
also increased only slightly to 1006 mb.

Peter has continued to move west-northwestward, or 295/12 kt. There
are no significant changes to the previous track forecast or
reasoning. Rose is expected to move around the southwestern and
western periphery of a subtropical ridge for the next couple of
days, followed by a slow northward motion on days 3-5 as the
cyclone moves through a weakness in the ridge induced by the
southward-moving former Tropical Storm Odette. The new NHC track
forecast is very similar to the previous advisory track, and lies
just to the east of the tightly packed consensus track models.

Some fluctuations in intensity will be possible during the next
24-36 hours owing to 5-10 kt fluctuations in the magnitude and also
the direction of the deep-layer vertical wind shear. However, by 48
hours and beyond, a slow weakening trend is expected due to the
shear increasing from the southwest and west-southwest of near 30
kt. The new official intensity forecast is essentially just an
update of the previous advisory, and closely follows the IVCN and
HCCA intensity consensus models.

Based on the latest track, intensity, and wind radii forecasts, no
tropical storm watches or warnings are required for the northern
Leeward Islands, Virgin Islands, or Puerto Rico at this time.
However, locally heavy rain is possible on Monday and Tuesday when
Peter is expected to pass to the north of these locations.


Key Messages:

Rainfall around the southern periphery of Tropical Storm Peter may
lead to areas of urban and small stream flooding through Tuesday
across Puerto Rico, the Virgin Islands, and the Northern Leeward
Islands.


FORECAST POSITIONS AND MAX WINDS

INIT  20/0900Z 19.1N  59.5W   45 KT  50 MPH
 12H  20/1800Z 19.7N  61.4W   40 KT  45 MPH
 24H  21/0600Z 20.4N  63.6W   40 KT  45 MPH
 36H  21/1800Z 21.4N  65.5W   35 KT  40 MPH
 48H  22/0600Z 22.4N  67.2W   35 KT  40 MPH
 60H  22/1800Z 23.2N  68.0W   30 KT  35 MPH
 72H  23/0600Z 24.2N  68.4W   30 KT  35 MPH
 96H  24/0600Z 26.2N  67.8W   25 KT  30 MPH
120H  25/0600Z 28.5N  66.8W   30 KT  35 MPH

$$
Forecaster Stewart
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