TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EDT THU SEP 16 2021

TROPICAL DISCUSSION FROM SEP 16/18 UTC: A TUTT LOW CENTERS OVER
SOUTHEAST CUBA/CAYMAN ISLANDS AND EXTENDS A TROUGH INTO COSTA RICA
AND NICARAGUA. UNDER THE PRESSURE OF A BUILDING SUBTROPICAL RIDGE
BETWEEN BERMUDA AND THE NORTHEAST CARIBBEAN...THE TROUGH IS
FORECAST TO MEANDER WESTWARD TO EXTEND OVER GUATEMALA/YUCATAN
PENINSULA ON SATURDAY. THIS WILL INITIALLY ENHANCE CONVECTION IN
HISPANIOLA/JAMAICA/SOUTHEAST CUBA AND COSTA RICA...BUT AS THE
RIDGE STRENGTHENS AND A DRIER AIR MASS MOVES IN FROM THE
EAST...EXPECT A NOTICEABLE DECREASE IN PRECIPITATION IN THE
GREATER ANTILLES FROM FRIDAY INTO EARLY NEXT WEEK...WHEN A ROBUST
TROPICAL WAVE ARRIVES INTO THE ISLAND CHAIN. UNDER THE INFLUENCE
OF ANOTHER TUTT FORECAST TO LINGER TO THE NORTH OF PUERTO
RICO/LEEWARD ISLANDS ON MONDAY/TUESDAY...EXPECT THE LARGEST
ACCUMULATIONS WITH THIS WAVE TO CLUSTER IN THE NORTHEAST CARIBBEAN
EARLY NEXT WEEK. IN THE MEAN TIME...THE CURRENT TUTT WILL STILL
FAVOR THE DEVELOPMENT OF STRONG CONVECTION IN NORTHERN HISPANIOLA
WHERE EXPECT 10-15MM/DAY AND MAXIMA OF 20-45MM THROUGH EARLY
FRIDAY. IN SOUTHEAST CUBA...JAMAICA AND THE CAYMAN ISLANDS EXPECT
05-10MM/DAY AND MAXIMA OF 15-20MM. IN WESTERN CUBA...THE TUTT WILL
INTERACT WITH A TROPICAL WAVE AND DIURNAL HEATING TO FAVOR
10-15MM/DAY AND MAXIMA OF 20-35MM. ON SATURDAY...EXPECT
ENHANCEMENT TO CLUSTER IN COSTA RICA AND NICARAGUA AS WELL AS
GUATEMALA/THE WESTERN AND NORTHERN YUCATAN PENINSULA...WHERE
EXPECT 10-15MM/DAY AND MAXIMA OF 20-35MM. ON SATURDAY...EXPECT
10-15MM/DAY AND MAXIMA OF 20-40MM FROM WESTERN EL SALVADOR INTO
VERACRUZ/CHIAPAS IN MEXICO.

IN MEXICO...UNDER CONTINUED VENTILATION BY THE SUBTROPICAL RIDGE
AND ENHANCEMENT BY THE LOW-LEVEL TROUGH ASSOCIATED WITH THE
REMNANTS OF NICHOLAS...EXPECT ENHANCE DIURNAL CONVECTION FROM
SOUTHERN SINALOA/NAYARIT INTO THE SIERRA MADRE ORIENTAL ON
THURSDAY AND FRIDAY. ENHANCED CONVECTION IS ALSO EXPECTED TO
DEVELOP FROM CAMPECHE/TABASCO/CHIAPAS AND GUATEMALA ON
THURSDAY...TO REACH JALISCO/NAYARIT/MICHOACAN BY SATURDAY IN
ASSOCIATION WITH A TRAIN OF TROPICAL WAVES. ON THURSDAY...EXPECT
10-15MM/DAY AND MAXIMA OF 20-35MM IN MOST OF CENTRAL MEXICO AND
NORTHEAST MEXICO. ALSO ON THURSDAY...A TROPICAL WAVE ENTERS
CHIAPAS/TABASCO FROM GUATEMALA...TO SUSTAIN 15-20MM/DAY AND MAXIMA
OF 30-60MM IN THESE REGIONS AND IN CAMPECHE. ON FRIDAY...THE
STRONGEST CONVECTION AND HEAVIEST PRECIPITATION IS EXPECTED IN
ASSOCIATION WITH THE TROPICAL WAVE...WHICH WILL FAVOR 15-20MM/DAY
AND MAXIMA OF 25-50MM FROM WESTERN CHIAPAS/VERACRUZ INTO
GUANAJUATO/MICHOACAN. IN TAMAULIPAS AND NUEVO LEON EXPECT
10-15MM/DAY AND MAXIMA OF 20-40MM. ON SATURDAY...EXPECT SIMILAR
AMOUNTS FROM GUERRERO WEST INTO NAYARIT AND JALISCO. IN EASTERN
SLOPES OF THE SIERRA MADRE ORIENTAL EXPECT 10-15MM/DAY AND MAXIMA
OF 20-40MM.

AN INCREASING TREND IS EXPECTED IN SOUTHERN CENTRAL AMERICA IN
ASSOCIATION WITH AN INCREASINGLY UPPER DIVERGENT PATTERN AS A CELL
OF THE SUBTROPICAL RIDGE EXPANDS INTO THE SOUTHWEST
CARIBBEAN...AND AN INTENSIFICATION OF THE PANAMANIAN LOW
CIRCULATION. AS LOW-LEVEL CONVERGENCE AND CYCLONIC VORTICITY
ASSOCIATED WITH THE CARIBBEAN LOW-LEVEL JET INCREASE BY
SATURDAY..EXPECT THE HEAVIEST PRECIPITATION IN THE CARIBBEAN BASIN
OF COSTA RICA/SOUTHERN NICARAGUA AND BOCAS DEL TORO...WITH
SCATTEDE AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. IN THE REST
OF PANAMA EXPECT MAXIMA OF 20-35MM...WHILE IN NORTHERN AND
NORTHWEST COLOMBIA EXPECT 15-20MM/DAY AND MAXIMA OF 25-50MM. IN
NORTHERN SOUTH AMERICA...EXPECT THE MOST ACTIVE CONVECTION IN
WESTERN AND SOUTHERN VENEZUELA/EASTERN COLOMBIA ON
FRIDAY...EXPANDING EASTWARD INTO SURINAME AND GUYANA ON
SATURDAY...TO SUSTAIN 10-15MM/DAY AND MAXIMA OF 20-35MM.

TROPICAL WAVES/TUTT INDUCED PERTURBATIONS/TRADE WIND SURGES
INITIALIZED AT 12 UTC:
TYPE  INIT 17/00 17/12 18/00 18/12 19/00 19/12 20/00 SOF
TW     39W   42W   45W   47W   50W   52W   54W   56W 14N  
TI     40W   43W   47W   50W   54W   57W   60W   62W 25N
TW     76W   79W   80W   83W   86W   89W   92W   95W 21N
TW     82W   85W   87W   89W   91W   94W   97W  100W 22N
TW     90W   91W   94W   96W   98W  101W  103W  106W 18N

A ROBUST TROPICAL WAVE IS INITIALIZED AT 39W. THIS WAVE IS BEING
MONITORED BY THE NHC FOR TROPICAL CYCLONE FORMATION. REGARDLESS OF
THE EVOLUTION...THIS PERTURBATION IS FORECAST TO ENHANCE
PRECIPITATION IN THE LEEWARD ISLANDS FROM LATE SUNDAY THROUGH THE
DAY ON MONDAY...AS IS INTERACTS WITH A TUTT LOCATED OVER THE
NORTHEAST CARIBBEAN BY THEN.

A TUTT-INDUCED PERTURBATION IS INITIALIZED AT 40W...TO THE SOUTH
OF 25N AND TO THE NORTH OF 14N. THIS WAVE IS FORECAST TO CROSS THE
LEEWARD ISLANDS DURING THE DAY ON SUNDAY TO PRODUCE A BRIEF PERIOD
OF PRECIPITATION. THE RAPID MOVEMENT OF THIS SYSTEM SHOULD LIMIT
ACCUMULATIONS TO 05-10MM/DAY AND MAXIMA OF 15-25MM.

A TROPICAL WAVE IS INITIALIZED ALONG 76W AND TO THE SOUTH OF 21N.
ON THURSDAY...THIS WILL FAVOR 10-15MM/DAY AND MAXIMA OF 20-35MM IN
SOUTHEAST CUBA...WHILE IN JAMAICA EXPECT 05-10MM/DAY AND MAXIMA OF
15-20MM. IN PANAMA EXPECT 05-10MM/DAY AND MAXIMA OF 15-20MM. ON
FRIDAY...THE WAVE WILL STIMULATE CONVECTION IN COSTA RICA AND
NICARAGUA TO FAVOR 10-15MM/DAY AND MAXIMA OF 20-35MM WHILE IN
EXTREME WESTERN CUBA EXPECT ISOLATED MAXIMA OF 15-25MM. ON
SATURDAY...IT WILL FAVOR 10-15MM/DAY AND MAXIMA OF 20-40MM FROM
WESTERN EL SALVADOR INTO CHIAPAS/TABASCO...WHILE IN THE WESTERN
AND NORTHERN YUCATAN PENINSULA IT FAVORS 05-10MM/DAY AND MAXIMA OF
15-25MM.

A TROPICAL WAVE ALONG 82W AND TO THE SOUTH OF 22N IS FORECAST TO
TRIGGER 10-15MM/DAY AND MAXIMA OF 20-40MM FROM WESTERN NICARAGUA
INTO EASTERN GUATEMALA/WESTERN HONDURAS ON THURSDAY. ON
FRIDAY...THIS WILL FAVOR 05-10MM/DAY AND MAXIMA OF 15-30MM IN THE
WESTERN YUCATAN PENINSULA AND GUATEMALA/WESTERN HONDURAS...WHILE
IN CHIAPAS AND TABASCO IT FAVORS 15-20MM/DAY AND MAXIMA OF
25-50MM. ON SATURDAY...EXPECT 10-15MM/DAY AND MAXIMA OF 20-40MM IN
VERACRUZ/EASTERN PORTIONS OF THE SIERRA MADRE ORIENTAL.

A TROPICAL WAVE IS INITIALIZED ALONG 90W AND SOUTH OF 18N.  ON
THURSDAY...THIS FAVORS 15-20MM/DAY AND MAXIMA OF 30-60MM IN
GUATEMALA AND CHIAPAS/TABASCO...WHILE TRAILING MOISTURE WILL FAVOR
MAXIMA OF 20-40MM IN EL SALVADOR AND WESTERN HONDURAS. ON FRIDAY
THIS WILL FAVOR 15-20MM/DAY AND MAXIMA OF 25-50MM FROM
CHIAPAS/VERACRUZ WEST INTO MICHOACAN AND GUANAJUATO IN
CENTRAL/SOUTHWEST MEXICO. ON SATURDAY THIS FAVORS 15-20MM/DAY AND
MAXIMA OF 25-50MM FROM GUERRERO/MORELOS/MEXICO THROUGH JALISCO AND
NAYARIT.

GALVEZ...WPC (USA)