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Tropical Discussion
 
(Latest Discussion - Issued 1803Z Sep 23, 2021)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 PM EDT THU SEP 23 2021

THE NHC IS ISSUING ADVISORIES FOR TROPICAL STORM SAM LOCATED IN
THE TROPICAL NORTH ATLANTIC. INFORMATION IS AVAILABLE THROUGH THE
NHC WEBSITE.

TROPICAL DISCUSSION FROM SEP 23/18 UTC: IN THE BAHAMAS...A SURFACE
TROUGH IS FORECAST TO CONTINUE LINGERING OVER THE REGION AHEAD OF
A SURFACE FRONT THAT IS FORECAST TO REMAIN NORTH OF THE ISLANDS
WHILE APPROACHING GRAND BAHAMA ON FRIDAY. THIS WILL FAVOR MODERATE
PRECIPITATION ON FRIDAY AND SATURDAY...WITH FORECAST AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM.

ELSEWHERE IN THE CARIBBEAN...A QUIET PATTERN IS EXPECTED THROUGH
SUNDAY UNDER THE INFLUENCE OF LIMITED AVAILABLE MOISTURE PRESENT
IN THE GREATER ANTILLES. MARGINAL ENHANCEMENT IS EXPECTED IN
HISPANIOLA ON THURSDAY UNDER THE INFLUENCE OF A SURFACE TROUGH
INDUCED BY WHAT WAS TROPICAL CYCLONE PETER. THIS WILL FAVOR
05-10MM/DAY AND MAXIMA OF 15-25MM. OTHER ACTIVITY IS EXPECTED WITH
WAVES IN THE TRADES. A TROUGH ENTERING THE LESSER ANTILLES ON
FRIDAY AND APPROACHING THE VIRGIN ISLANDS ON SATURDAY WILL TRIGGER
05-10MM/DAY AND MAXIMA OF 15-25MM IN THE CENTRAL LESSER ANTILLES
ON SATURDAY...WHILE TRIGGERING MAXIMA OF 15MM IN THE LEEWARD AND
VI...AS WELL AS IN THE WINDWARD ISLANDS.

IN THE SOUTHERN CARIBBEAN...AN INTENSIFICATION OF THE TRADES IS
FORECAST TO ENHANCE LOW-LEVEL CONVERGENCE AND CYCLONIC VORTICITY
TO THE NORTH OF PANAMA ON FRIDAY...TO DEVELOP A SURFACE TROUGH.
THE TROUGH IS THEN FORECAST TO ARRIVE INTO EASTERN NICARAGUA ON
SATURDAY...TO FAVOR MODERATE PRECIPITATION FROM SAN ANDRES AND
PROVIDENCIA INTO CENTRAL HONDURAS AND CENTRAL NICARAGUA FROM
SATURDAY INTO SUNDAY...WHEN EXPECTING 15-20MM/DAY AND MAXIMA OF
25-50MM.

IN NORTHERN SOUTH AMERICA...CONVECTION IS FORECAST TO ORGANIZE
PRIMARILY WITH WAVES IN THE TRADES (SEE BELOW). INITIALLY...EXPECT
MODERATE ACCUMULATIONS IN NORTHWEST AND NORTHERN COLOMBIA...AS
WELL AS PANAMA AND SOUTHERN COSTA RICA...IN ASSOCIATION WITH A
TROPOSPHERIC KELVIN WAVE. THIS WILL FAVOR 15-20MM/DAY AND MAXIMA
OF 30-60MM IN COLOMBIA WHILE IN PANAMA/COSTA RICA AND EXTREME
NORTHERN COLOMBIA EXPECT 10-15MM/DAY AND MAXIMA F 20-45MM.

TROPICAL WAVES/TUTT INDUCED PERTURBATIONS/TRADE WIND SURGES
INITIALIZED AT 12 UTC:
TYPE  INIT 24/00 24/12 25/00 25/12 26/00 26/12 27/00 SOF
TW     61W   65W   68W   72W   74W   76W   79W   81W 11N
EW     81W   83W   85W   87W   89W   91W   94W   96W 22N

A TROPICAL WAVE ALONG 61W AND SOUTH OF 10N IS FORECAST TO ENHANCE
CONVECTION MOSTLY IN NORTHERN SOUTH AMERICA ON THURSDAY...TO FAVOR
MAXIMA OF 15-25MM IN SOUTHERN AND WESTERN VENEZUELA...AND MAXIMA
OF 15MM IN NORTHERN VENEZUELA. ON FRIDAY...THIS WILL SUSTAIN
15-20MM/DAY AND ISOLATED MAXIMA OF 25-50MM FROM NORTH-CENTRAL
VENEZUELA INTO THE LAKE MARACAIBO REGION WHILE IN NORTHERN
COLOMBIA IT FAVORS MAXIMA OF 15-30MM. ON FRIDAY...THIS WILL FAVOR
MAXIMA OF 15-30MM IN NORTHWEST COLOMBIA AND PANAMA.

AN EASTERLY WAVE ALONG 81W IS FORECAST TO ENHANCE DIURNAL
CONVECTION IN WESTERN CUBA ON THURSDAY TO FAVOR MAXIMA OF 15-25MM.
IN EASTERN HONDURAS AND EASTERN NICARAGUA IT WILL FAVOR MAXIMA OF
15-20MM. ON FRIDAY...IT WILL FAVOR MAXIMA OF 20-35MM IN MOST OF
NICARAGUA...EL SALVADOR AND GUATEMALA...WHILE IN NORTHWEST
HONDURAS IT FAVORS MAXIMA OF 15-20MM. ON SATURDAY...IT WILL FAVOR
MAXIMA OF 20-35MM FROM NORTHWEST HONDURAS INTO SOUTHERN
VERACRUZ...WHILE IN THE YUCATAN PENINSULA IT FAVORS MAXIMA OF
15-20MM. IN EL SALVADOR AND SOUTHERN GUATEMALA THE WAVE IS TO
FAVOR MAXIMA OF 15-25MM.

GALVEZ...WPC (USA)