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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1812Z Sep 15, 2020)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
212 PM EDT TUE SEP 15 2020

AT 15 UTC...HURRICANE SALLY CENTERED NEAR 29.1N 88.2W. MINIMUM
CENTRAL PRESSURE WAS ESTIMATED AT 983 HPA. MAXIMUM SUSTAINED WINDS
WERE AT 75KT WITH GUSTS TO 100KT. SALLY WAS MOVING TO THE
NORTHWEST OR AT 315 DEGREES AND AT 02KT.

TROPICAL DISCUSSION FROM SEPTEMBER 15/18 UTC: IN THE UPPER
LEVELS...A LARGE CELL OF THE SUBTROPICAL RIDGE CENTERS OVER THE
GULF OF MEXICO WHILE ANOTHER CELL CENTERS TO THE WEST OF THE BAJA
CALIFORNIA PENINSULA. A POLAR TROUGH LIES IN BETWEEN THESE
SYSTEMS...EXTENDING ACROSS NEW MEXICO INTO NORTHERN MEXICO. AS THE
TROUGH DIGS THROUGH THE CYCLE...IT WILL PLAY A ROLE IN ENHANCING
CONVECTION IN NORTHERN MEXICO. HOWEVER...LARGER RAINFALL
ACCUMULATIONS ARE EXPECTED TO THE SOUTH OF 23N...WHERE DEEP-LAYER
MOISTURE IS PRESENT. FURTHERMORE...A TROPICAL WAVE WILL PROVIDE
ADDITIONAL STIMULATION AS IT PROPAGATES FROM VERACRUZ ON
MONDAY...TO MICHOACAN/JALISCO BY WEDNESDAY. THE INDIRECT EFFECTS
OF SALLY WILL ALSO LEAD TO LOCALLY HEAVY RAINFALL...AS IT
STIMULATES ONSHORE FLOW ALONG THE GULF OF MEXICO...AND FAVORS THE
DEVELOPMENT OF FEEDER BANDS TO INTERACT WITH THE DIURNAL CYCLE OF
HEATING IN THE YUCATAN PENINSULA.

ON THE EXPECTED ACCUMULATIONS...ON TUESDAY...THE STRONGEST
CONVECTION IS EXPECTED ALONG THE COAST OF NORTHEAST MEXICO IN
ASSOCIATION WITH SALLY...AND FROM WESTERN JALISCO INTO SINALOA IN
ASSOCIATION WITH A SURFACE TROUGH. EXPECTING 15-20MM/DAY AND
MAXIMA OF 25-50MM. ACTIVE CONVECTION IS EXPECTED ALSO IN SOUTHERN
MEXICO FROM VERACRUZ INTO MICHOACAN/COLIMA AND IN THE YUCATAN
PENINSULA/CAMPECHE/CHIAPAS/TABASCO WHERE EXPECTING 10-15MM/DAY AND
MAXIMA OF 20-45MM. ON WEDNESDAY...LARGEST AMOUNTS WILL CLUSTER IN
THE YUCATAN PENINSULA AND IN MOST OF CENTRL MEXICO TO THE SOUTH OF
22N...WHERE EXPECTING 15-20MM/DAY AND MAXIMA OF 30-60MM. IN
CHIAPAS/TABASCO EXPECTING 10-15MM/DAY AND MAXIMA OF 20-40MM. ON
THURSDAY...LARGEST ACCUMULATIONS WILL CLUSTER IN VERACRUZ/SIERRA
MADRE ORIENTAL WHERE EXPECTING 15-20MM/DAY AND MAXIMA OF 35-70MM.
TROPICAL WAVE CONVECTION IN WESTERN MEXICO WILL SUSTAIN
15-20MM/DAY AND MAXIMA OF 30-60MM...WHILE CONVECTION IN NORTHEAST
MEXICO SUSTAINS 05-10MM/DAY AND MAXIMA OF 15-25MM.

IN THE CARIBBEAN AND AT UPPER LEVELS...A TUTT CENTERS TO THE NORTH
OF HISPANIOLA AT 27N 69W...AND EXTENDS AN AXIS INTO CENTRAL
HISPANIOLA. THIS IS INTERACTING WITH AN INDUCED PERTURBATION TO
TRIGGER CONVECTION IN HISPANIOLA ON TUESDAY...WHERE EXPECTING
15-20MM/DAY AND MAXIMA OF 30-60MM. THE TUTT SOUTHERN AXIS IS
FORECAST TO MOVE LITTLE THROUGH THE CYCLE...AS ITS WESTWARD
PROGRESSION IS BLOCKED BY THE ROBUST UPPER RIDGE OVER THE GULF OF
MEXICO AND CUBA/BAHAMAS. AS IT MEANDERS SLOWLY WESTWARD TO EXTEND
OVER CENTRAL CUBA BY THURSDAY...IT WILL PROVIDE ENHANCEMENT TO
HISPANIOLA...JAMAICA...AND SOUTHEAST CUBA IN UNISON WITH THE
INDUCED PERTURBATION. THE LIMITATION IS AVAILABLE MOISTURE. THIS
WILL LIMIT POTENTIAL ACCUMULATIONS TO 10-15MM/DAY AND MAXIMA OF
20-40MM IN HISPANIOLA ON WEDNESDAY...DECREASING SHARPLY ON
THURSDAY. OVER JAMAICA...EXPECTING 05-10MM/DAY AND MAXIMA OF
15-20MM ON WEDNESDAY INCREASING TO 05-10MM/DAY AND SCATTERED
MAXIMA OF 15-25MM ON THURSDAY. SIMILAR AMOUNTS ARE EXPECTED TO
DEVELOP IN SOUTHEAST CUBA ON THURSDAY.

ELSEWHERE IN THE CARIBBEAN...CONVECTION IS FORECAST TO DEVELOP IN
ASSOCIATION WITH THE FEEDER BANDS OF TROPICAL CYCLONE
TEDDY...LOCATED OVER THE TROPICAL ATLANTIC AND FORECAST TO AVOID
THE CARIBBEAN. ON TUESDAY INTO EARLY WEDNESDAY...A FEEDER BAND
WILL SUSTAIN ISOLATED CONVECTION IN THE WINDWARD ISLANDS TO FAVOR
05-10MM/DAY AND ISOLATED MAXIMA OF 15-25MM. ON
THURSDAY...EXPECTING 05-10MM/DAY AND MAXIMA OF 15-30MM IN TRINIDAD
AND TOBAGO AND THE NORTHERN COAST OF VENEZUELA. ON
THURSDAY...FEEDER BAND CONVECTION WILL AFFECT PUERTO RICO AND THE
VIRGIN ISLANDS TO FAVOR SCATTERED ACCUMULATIONS OF 05-10MM/DAY AND
MAXIMA OF 15-25MM.

NORTHERN SOUTH AMERICA WILL ALSO FEEL THE EFFECTS OF TEDDY IN THE
FORM OF FEEDER BAND CONVECTION. THIS...IN COMBINATION WITH THE
NET/ITCZ...WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 30-60MM IN
FRENCH GUIANA AND SURINAME ON TUESDAY...WHILE NET CONVECTION TO
THE WEST FROM CENTRAL GUYANA INTO SOUTHERN VENEZUELA/EASTERN
COLOMBIA LEADS TO 10-15MM/DAY AND MAXIMA OF 20-45MM. ON
WEDNESDAY...NET CONVECTION IN NORTHERN GUYANA AND SOUTHEAST
VENEZUELA WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 25-50MM. THIS
DECREASES ON THURSDAY TO 05-10MM/DAY AND MAXIMA OF 15-30MM IN
NORTHERN GUYANA AND MOST OF SOUTHEAST AND CENTRAL VENEZUELA. TO
THE WEST...IN COLOMBIA...CONVECTION WILL PEAK IN THE LOWER
MAGDALENA VALLEY AND EJE CAFETERO/WESTERN COLOMBIA IN ASSOCIATION
WITH AN ACTIVE PANAMANIAN LOW AND ASSOCIATED WESTERLIES/ONSHORE
FLOW IN WESTERN COLOMBIA. ON TUESDAY...EXPECTING 15-20MM/DAY AND
MAXIMA OF 25-50MM. THIS INCREASES TO 15-20MM/DAY AND MAXIMA OF
30-60MM ON WEDNESDAY. ON THURSDAY...STRONGEST CONVECTION IS
EXPECTED IN SOUTHWEST COLOMBIA/VALLE DEL CAUCA TO SUSTAIN
15-20MM/DAY AND MAXIMA OF 25-50MM. ACTIVE CONVECTION IS ALSO
EXPECTED IN NORTHERN COLOMBIA/LAKE MARACAIBO REGION IN VENEZUELA
ON THURSDAY...WHERE THE NET WILL FAVOR 10-15MM/DAY AND MAXIMA OF
20-40MM.

IN CENTRAL AMERICA...AN INCREASING TREND IS EXPECTED IN
ASSOCIATION WITH A TROPICAL WAVE THAT ARRIVES INTO PANAMA ON
TUESDAY AND COSTA RICA/NICARAGUA ON WEDNESDAY. IN COMBINATION WITH
THE ITCZ...LARGEST ACCUMULATIONS ARE EXPECTED IN COSTA RICA AND
PANAMA. ON WEDNESDAY...EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM
IN COSTA RICA AND PANAMA...WHILE IN NICARAGUA...HONDURAS AND EL
SALVADOR EXOECTING 05-10MM/DAY AND MAXIMA OF 15-25MM. IN GUATEMALA
EXPECTING MAXIMA OF 20-40MM AS A MOISTURE POOL REMAINS AND
VENTILATION CONTINUES FAVORABLE IN THE SOUTHERN PERIPHERY OF THE
UPPER RIDGE IN THE GULF OF MEXICO. ON WEDNESDAY...CONVECTION IN
COSTA RICA INCREASES TO SUSTAIN 10-15MM/DAY AND MAXIMA OF 20-40MM
IN WESTERN COSTA RICA AND WESTERN PANAMA. IN WESTERN
NICARAGUA...EL SALVADOR INTO GUATEMALA/WESTERN HONDURAS EXPECTING
05-10MM/DAY AND MAXIMA OF 15-30MM. ON FRIDAY...EXPECTING A PEAK IN
CONVECTION IN WESTERN PANAMA AND SOUTHERN COSTA RICA TO SUSTAIN
15-20MM/DAY AND MAXIMA OF 25-50MM...WHILE IN EASTERN PANAMA AND IN
NORTHERN COST RICA...WESTERN NICARAGUA AND HONDURAS EXPECTING
05-10MM/DAY AND MAXIMA OF 15-30MM. IN WESTERN EL SALVADOR AND
GUATEMALA...THE TROPICAL WAVE WILL FAVOR 10-15MM/DAY AND MAXIMA OF
20-40MM.


TROPICAL WAVES/TUTT INDUCED PERTURBATIONS/TRADE WIND SURGES
TYPE  15/12  16/00  16/12  17/00  17/12  18/00  18/12  19/00  SOF
TW      74W    77W    80W    83W    86W    90W    93W    96W  20N
TW      95W    97W    99W   100W   102W   104W   106W   108W  19N

A TROPICAL WAVE IS INITIALIZED AT 74W AND TO THE SOUTH OF 20N. 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. ON THURSDAY...THIS
WILL FAVOR 10-15MM/DAY AND MAXIMA OF 20-40MM FROM WESTERN
HONDURAS/WESTERN EL SALVADOR INTO MOST OF GUATEMALA AND CHIAPAS.
TRAILING MOISTURE WUL FAVOR 05-10MM/DAY AND MAXIMA OF 15-30MM IN
NORTHERN COSTA RICA AND WESTERN NICARAGUA/GULF OF FONSECA REGION.

A TROPICAL WAVE IS INITIALIZED AT 95W AND TO THE SOUTH OF 19N. 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. ON THUSDAY...THE
TROPICAL WAVE WILL FAVOR 15-20MM/DAY AND MAXIMA OF 25-50MM IN
WESTERN MEXICO.

GALVEZ/DAVISON...WPC (USA)