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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1820Z Sep 14, 2020)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
220 PM EDT MON SEP 14 2020

AT 15 UTC...HURRICANE SALLY CENTERED NEAR 28.7N 87.0W. MINIMUM
CENTRAL PRESSURE WAS ESTIMATED AT 986 HPA. MAXIMUM SUSTAINED WINDS
WERE AT 80KT WITH GUSTS TO 100KT. SALLY WAS MOVING TO THE
WEST-NORTHWEST OR AT 285 DEGREES AND AT 06KT.

TROPICAL DISCUSSION FROM SEPTEMBER 14/18 UTC: A MASSIVE CELL OF
THE SUBTROPICAL UPPER RIDGE CENTERS OVER THE GULF OF MEXICO. THIS
CELL IS FORECAST TO HOLD AND EXPAND EASTWARD...TO BLOCK THE
WESTWARD PROGRESSION OF A TUTT CURRENTLY TO THE NORTH OF
HISPANIOLA. ALSO...THIS WILL SUSTAIN MODERATE 25-50KT
NORTHEASTERLY FLOW IN THE UPPER TROPOSPHERE OVER THE BAHAMAS AND
CUBA AND NORTHERN CENTRAL AMERICA THROUGH THE CYCLE.

IN THE LOWER LEVELS AND NORTHWEST IN THE DOMAIN...A TROPICAL WAVE
IS PROPAGATING VERY SLOWLY ACROSS CHIAPAS/TABASCO...TO PROVIDE
ENHANCEMENT OF PRECIPITATION AS IT MOVES WESTWARD ACROSS SOUTHERN
AND CENTRAL MEXICO. ALSO...NORTHEASTERLY TRADES IN ASSOCIATION
WITH HURRICANE SALLY ARE EXPECTED TO ENHANCE MOISTURE CONVERGENCE
ALONG THE SIERRA MADRE ORIENTAL AND COASTAL LOCATIONS IN NORTHEAST
MEXICO. A LAST REGION OF INTEREST IS THE SIERRA MADRE
OCCIDENTAL...WHERE SEASONAL CONVECTION IS BEING STIMULATED BY
TROUGH PATTERN TO THE NORTH. ON MONDAY...LARGEST ACCUMULATIONS IN
MEXICO ARE EXPECTED IN CENTRAL PORTIONS OF THE SIERRA MADRE
ORIENTAL AND EASTERN SLOPES...WHERE EXPECTING 15-30MM/DAY AND
MAXIMA OF 40-80MM. IN NORTHEAST MEXICO EXPECTING MAXIMA OF
20-40MM. TROPICAL WAVE WILL FAVOR 15-20MM/DAY AND MAXIMA OF
30-60MM IN CHIAPAS/TABASCO/CAMPECHE AND IN SOUTHERN OAXACA. IN THE
YUCATAN PENINSULA...DIURNAL CONVECTION WILL FAVOR MAXIMA OF
20-40MM. IN WESTERN MEXICO...CONVECTION IN THE SIERRA MADRE
OCCIDENTAL WILL FAVOR 15-20MM/DAY AND ISOLATED MAXIMA OF 25-50MM
IN SOUTHERN CHIHUAHUA/DURANGO. ON TUESDAY...TROPICAL WAVE
CONVECTION ALONG THE GULF COAST OF MEXICO WILL FAVOR 15-20MM/DAY
AND MAXIMA OF 30-60MM. TRAILING MOISTURE IN THE YUCATAN PENINSULA
AND CHIAPAS/TABASCO WILL FAVOR 10-15MM/DAY AND MAXIMA OF 20-40MM.
TO THE WEST...A SURFACE TROUGH WILL STIMULATE CONVECTION IN
JALISCO/COLIMA/NAYARIT...TO FAVOR 15-20MM/DAY AND MAXIMA OF
25-50MM...WHILE IN THE SIERRA MADRE OCCIDENTAL EXPECTING A
DECREASE TO 05-10MM/DAY AND MAXIMA OF 15MM. ON
WEDNESDAY...TROPICAL WAVE...MOIST PLUME AND IMPROVED VENTILATION
WILL FAVOR A WET PATTERN IN MOST OF CENTRAL AND SOUTHWEST
MEXICO...TO FAVOR 15-20MM/DAY AND SCATTERED MAXIMA OF 25-50MM FROM
VERACRUZ WEST INTO NAYARIT/SINALOA. DIURNAL CONVECTION IN THE
YUCATAN PENINSULA WILL FAVOR 10-15MM/DAY AND MAXIMA OF 25-50MM.

TO THE EAST...IN THE CARIBBEAN...A TROPICAL WAVE WILL BE THE MAJOR
PLAYER IN THE MODULATION OF CONVECTION AS IT PROPAGATES FROM
HISPANIOLA ON MONDAY INTO CENTRAL AMERICA/WESTERN CUBA BY
WEDNESDAY. INITIALLY...LARGEST ACCUMULATIONS ARE EXPECTED IN
HISPANIOLA AS THE TROPICAL WAVE INTERACTS WITH OROGRAPHY AND TUTT
TO THE NORTH. THIS WILL FAOR 10-15MM/DAY AND MAXIMA OF 20-40MM ON
MONDAY INTO EARLY TUESDAY. ISOLATED SIMILAR AMOUNTS ARE EXPECTED
IN PUERTO RICO. ALSO ON MONDAY...DIURNAL CONVECTION IN WESTERN
HAITI...AND CUBA WILL FAVOR 05-10MM/DAY AND MAXIMA OF
15-20MM...WHILE IN JAMAICA EXPECTING MAXIMA OF 15MM. ON
TUESDAY...AN INDUCED TROUGH IS FORECAST TO BECOME BETTER DEFINED
AND SUSTAIN A PEAK IN ACTIVITY IN THE DOMINICAN REPUBLIC...WHERE
EXPECTING 15-20MM/DAY AND MAXIMA OF 30-60MM. TROPICAL WAVE
CONVECTION IN JAMAICA AND IN HAITI WILL FAVOR 05-10MM/DAY AND
MAXIMA OF 15-25MM...WHILE IN SOUTHEAST CUBA AND IN THE TURKS AND
CAICOS EXPECTING MAXIMA OF 15MM. IN PUERTO RICO...TRAILING
MOISTURE WILL ALLOW FOR DIURNAL CONVECTION TO SUSTAIN 05-10MM/DAY
AND MAXIMA OF 15-25MM. ON WEDNESDAY...LARGEST ACCUMULATIONS ARE
EXPECTED IN HAITI IN ASSOCIATION WITH THE INDUCED TROUGH...WHERE
AMOUNTS ARE LIKELY TO REACH 10-15MM/DAY AND MAXIMA OF 20-40MM. THE
TROUGH WILL STIMULATE CONVECTION IN THE TURKS AND CAICOS AND IN
THE SOUTHEAST BAHAMAS TO FAVOR 05-10MM/DAY AND MAXIMA OF 15-20MM.
SIMILAR AMOUNTS ARE EXPECTED IN WESTERN CUBA IN ASSOCIATION WITH
THE TROPICAL WAVE. IN PUERTO RICO...EXPECTING A DECREASE IN MAXIMA
TO 15MM.

IN CENTRAL AMERICA...THE INFLUENCE OF WEAKENED TRADES WILL ENHANCE
THE DIURNAL CYCLE OF CONVECTION...ESPECIALLY ALONG THE PACIFIC
BASIN AND THE CONTINENTAL DIVIDE. THIS WILL FAVOR 10-15MM/DAY AND
MAXIMA OF 20-40MM FROM WESTERN COSTA RICA INTO SOUTHERN
GUATEMALA/EL SALVADOR AND WESTERN HONDURAS ON MONDAY...WHILE IN
PANAMA EXPECTING 05-10MM/DAY AND MAXIMA OF 15-30MM. ON TUESDAY...A
DRIER AIR MASS ENTERS FROM THE CARIBBEAN TO DECREASE ACCUMULATIONS
TO 05-10MM/DAY AND MAXIMA OF 15-25MM ACROSS NICARAGUA/EL
SALVADOR/HONDURAS...WHILE IN PANAMA AND COSTA RICA EXPECTING
10-15MM/DAY AND MAXIMA OF 20-35MM. A TROPICAL WAVE APPROACHES ON
WEDNESDAY. THIS WILL SUSTAIN AN INCREASE IN WESTERN PANAMA AND
SOUTHERN COSTA RICA TO 10-15MM/DAY AND MAXIMA OF 20-40MM. SIMILAR
AMOUNTS ARE EXPECTED IN THE GULF OF FONSECA REGION...WHERE IN
EASTERN HONDURAS AND EASTERN NICARAGUA EXPECTING 05-10MM/DAY AND
SCATTERED MAXIMA OF 15-20MM.

IN NORTHERN SOUTH AMERICA...CONVECTION WILL BE PRIMARILY
STIMULATED ALONG THE NET. A TROPICAL WAVE CURRENTLY PROPAGATING
ACROSS WESTERN VENEZUELA WLL ALSO PROVIDE SOME STIMULATION TO
CONVECTION IN COLOMBIA...WHILE THE INDIRECT EFFECTS OF TROPICAL
CYCLONE TEDDY WILL STIMULATE CONVECTION IN THE GUIANAS AND ALONG
THE NORTHERN COAST OF VENEZUELA/WINDWARD ISLANDS LATER IN THE
CYCLE. ON MONDAY...EXPECTING LARGEST ACCUMULATIONS ALONG THE NET
AND AMAZON BASIN IN VENEZUELA...AS WELL AS IN THE LOWER MAGDALENA
VALLEY IN COLOMBIA...WHERE EXPECTING 10-15MM/DAY AND MAXIMA OF
20-40MM. IN WESTERN COLOMBIA EXPECTING 05-10MM/DAY AND MAXIMA OF
15-20MM...WHILE ELSEWHERE EXPECTING GENERALLY MAXIMA OF 15-20MM.
ON TUESDAY...THE TROPICAL WAVE WILL STIMULATE CONVECTION IN
NORTHERN...CENTRAL AND WESTERN COLOMBIA WHERE IT WILL FAVOR
15-20MM/DAY AND MAXIMA OF 30-60MM. SIMILAR AMOUNTS ARE EXPECTED IN
FRENCH GUIANA AND IN SURINAME IN ASSOCIATION WITH A TROUGH INDUCED
BY TEDDY. IN SOUTHERN VENEZUELA/EASTERN COLOMBIA EXPECTING
10-15MM/DAY AND MAXIMA OF 20-45MM. ON WEDNESDAY...LARGEST
ACCUMULATIONS ARE EXPECTED IN CENTRAL AND WESTERN COLOMBIA...WHERE
AMOUNTS ARE FORECAST TO REACH 15-20MM/DAY AND MAXIMA OF 30-60MM.
ENHANCED CONVECTION IS ALSO EXPECTED ALONG A WEAKENING BRANCH OF
THE NET IN CANAIMA/WESTERN GUYANA...WHERE EXPECTING 15-20MM/DAY
AND MAXIMA OF 25-50MM. AS THE NET REFORMS ALONG NORTHERN
VENEZUELA...EXPECTING AN INCREASE IN ACCUMULATIONS TO SUSTAIN
05-10MM/DAY AND MAXIMA OF 15-30MM. SIMILAR AMOUNTS ARE EXPECTED IN
NORTHERN AND EASTERN COLOMBIA...AND EASTERN VENEZUELA.

TROPICAL WAVES/TUTT INDUCED PERTURBATIONS/TRADE WIND SURGES
TYPE  14/12  15/00  15/12  16/00  16/12  17/00  17/12  18/00  SOF
TW      68W    71W    74W    77W    80W    83W    86W    90W  20N
TW      91W    93W    95W    97W    99W   100W   102W   104W  19N

A TROPICAL WAVE IS INITIALIZED AT 68W AND TO THE SOUTH OF 20N.
THIS WAVE IS CURRENTLY INTERACTING WITH A TUTT TO THE NORTH OF
HISPANIOLA...BUT WILL CONTINUE ITS PROPAGATION WESTWARD TO
STIMULATE CONVECTION SLIGHTLY AS IT MOVES FROM THE CENTRAL
CARIBBEAN ON MONDAY INTO CENTRAL AMERICA ON WEDNESDAY AND
THURSDAY. ON MONDAY...THE WAVE WILL FAVOR 10-15MM/DAY AND MAXIMA
OF 20-40MM IN HISPANIOLA AND PUERTO RICO...AS WELL AS IN THE BAJO
MAGDALENA IN COLOMBIA. IN NORTHERN COLOMBIA AND WESTERN VENEZUELA
IT WILL FAVOR 05-10MM/DAY AND MAXIMA OF 15-25MM. ON TUESDAY...THE
TROPICAL WAVE WILL FAOR 05-10MM/DAY AND MAXIMA OF 15-25MM IN
JAMAICA...WHILE IN NORTHERN...CENTRAL AND WESTERN COLOMBIA IT
FAVORS 15-20MM/DAY AND MAXIMA OF 30-60MM. IN PANAMA EXPECTING
10-15MM/DAY AND MAXIMA OF 20-35MM. ON WEDNESDAY...THE TROPICAL
WAVE WILL STIMULATE CONVECTION IN WESTERN PANAMA AND WESTERN COSTA
RICA TO FAVOR 10-15MM/DA AND MAXIMA OF 20-40MM. SIMILAR AMOUNTS
ARE EXPECTED IN THE GULF OF FONSECA REGION...WHILE IN WESTERN CUBA
AND IN EASTERN HONDURAS/NICARAGUA EXPECTING 05-10MM/DAY AND
SCATTERED MAXIMA OF 15-20MM.

A TROPICAL WAVE IS PROPAGATING SLOWLY ACROSS THE GULF OF
TEHUANTEPEC REGION...AS IS INITIALIZED AT 91W AND TO THE SOUTH OF
19N. THIS WAVE WILL STIMULATE CONVECTION IN NORTHERN CENTRAL
AMERICA AND SOUTHERN MEXICO ON MONDAY. IN EL
SALVADOR/HONDURAS/SOUTHERN GUATEMALA EXPECTING 10-15MM/DAY AND
MAXIMA OF 20-40MM...WHILE IN WESTERN GUATEMALA/CHIAPAS/TABASCO AND
IN OAXACA EXPECTING 15-20MM/DAY AND MAXIMA OF 30-60MM. ON
TUESDAY...THE WAVE WILL STIMULATE CONVECTION IN VERACRUZ/PUEBLA
WHERE IT WILL FAVOR 15-20MM/DAY AND MAXIMA OF 30-60MM. ON
WEDNESDAY...STIMULATION WILL FOCUS IN CENTRAL MEXICO...WHERE
EXPECTING 15-20MM/DAY AND SCATTERED MAXIMA OF 25-50MM FROM
VERACRUZ/OAXACA WEST INTO
JALISCO/COLIMA/MICHOACAN/GUANAJUATO/ZACATECAS.

GALVEZ/DAVISON...WPC (USA)