Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center
 
Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1701Z Sep 17, 2020)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product


TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
101 PM EDT THU SEP 17 2020

AT 15 UTC...HURRICANE TEDDY CENTERED NEAR 19.3N 53.0W. MINIMUM
CENTRAL PRESSURE WAS 957 HPA AND MAXIMUM SUSTAINED WINDS 105KT
WITH GUSTS UP TO 130KT. TEDDY WAS MOVING TO THE NORTHWEST OR AT
325 DEGREES AND AT 10KT.

TROPICAL DISCUSSION FROM SEPTEMBER 17/18 UTC: A DRYING TREND IS
EXPECTED IN MEXICO. IN THE UPPER LEVELS...A ROBUST POLAR TROUGH IS
PROPAGATING WESTWARD ACROSS NORTHERN MEXICO...TO EXTEND FROM
OKLAHOMA INTO NUEVO LEON ON THURSDAY...EAST TEXAS INTO COASTAL
TAMAULIPAS ON FRIDAY...TO THEN EXIT INTO THE GULF OF MEXICO. THE
TROUGH WILL STIMULATE CONVECTION IN EASTERN MEXICO ON THURSDAY AND
FRIDAY. HOWEVER...NORTH AND NORTHWESTERLY FLOW IN THE MID AND
UPPER LEVELS IS FORECAST TO ADVECT A DRY AIR MASS FROM THE
SOUTHWEST US INTO MOST OF NORTHERN MEXICO...TO RESULT IN A
SUBSTANTIAL DRYING TREND IN MOST OF CENTRAL AND NORTHERN MEXICO
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. AT LOW AND MID
LEVELS...TROPICAL WAVES ARE STIMULATING PRECIPITATION AS THEY
PROPAGATE ACROSS SOUTHERN AND CENTRAL MEXICO. FURTHERMORE...A
PERTURBATION LOCATED IN THE SOUTHERN GULF OF MEXICO...BEING
MONITORED BY THE NATIONAL HURRICANE CENTER...IS FAVORING ONSHORE
FLOW INTO THE SIERRA MADRE ORIENTAL...WHICH WILL LEAD TO MODERATE
RAINFALL ACCUMULATIONS THROUGH THE FORECAST CYCLE. ON
THURSDAY...EXPECTING 15-20MM/DAY AND MAXIMA OF 35-70MM ALONG THE
GULF COAST AND EASTERN SLOPES OF SIERRA MADRE ORIENTAL FROM
SOUTHERN TAMAULIPAS INTO OAXACA/VERACRUZ. IN CENTRAL AND WESTERN
MEXICO...TROPICAL WAVE CONVECTION WILL FAVOR 15-20MM/DAY AND
MAXIMA OF 30-60MM. IN NORTHEAST MEXICO...THE UPPER TROUGH WILL
STIMULATE CONVECTION TO FAVOR 05-10MM/DAY AND MAXIMA OF 15-25MM.
ALSO ON THURSDAY...ANOTHER TROPICAL WAVE WILL STIMULATE CONVECTION
IN THE YUCATAN PENINSULA TO FAVOR 05-10MM/DAY AND MAXIMA OF
15-25MM. ON FRIDAY...THE LARGEST ACCUMULATIONS ARE EXPECTED IN
ASSOCIATION WITH THE TROPICAL WAVE PROPAGATING ACRROSS THE
TEHUANTEPEC REGION. THIS WILL FAVOR 15-20MM/DAY AND MAXIMA OF
25-50MM FROM WESTERN CHIAPAS/TABASCO INTO NORTHERN VERACRUS AND
CENTRAL MEXICO. IN WESTERN MEXICO EXPECTING 10-15MM/DAY AND MAXIMA
OF 20-35MM...WHILE IN NORTHEAST MEXICO EXPECTING 05-10MM/DAY AND
MAXIMA OF 15-20MM. ON SATURDAY...EXPECTING 15-20MM/DAY AND MAXIMA
OF 30-60MM IN CHIAPAS AND TABASCO...WHILE IN THE YUCATAN PENINSULA
EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM. IN SOUTHERN AND
CENTRAL MEXICO...THE TROPICAL WAVE WILL FAVOR 10-15MM/DAY AND
MAXIMA OF 20-40MM.

TO THE EAST...A ROBUST UPPER RIDGE CENTERS OVER THE EASTERN GULF
OF MEXICO. THIS IS LEDING TO NORTHERLY FLOW IN AREAS BETWEEN THE
BAHAMAS AND BERMUDA...WHICH IS AMPLIFYING AN UPPER TROUGH TO THE
EAST. THE UPPER TROUGH IS FORECAST TO FORM A TUTT LOW THAT IS
EXPECTED TO MEANDER NORTH OF PUERTO RICO AND HISPANIOLA DURING THE
WEEKEND...TO PROVIDE SOME ENHANCEMENT OF CONVECTION.
HOWEVER...AVAILABLE MOISTURE WILL BE LIMITED...WHICH IS EXPECTED
TO FAVOR LIMITED COVERAGE OF CONVECTIVE CELLS. TO THE WEST OF
THESE LOCATIONS...A MOIST PLUME IS MOVING WESTWARD ACROSS
JAMAICA...SOUTHEAST CUBA AND THE CAYLAN ISLANDS ON THURSDAY.
YET...A MUCH DRIER AIR MASS TRAILS...TO FAVOR A DECREASE IN THE
COVERAGE OF CONVECTION DURING THE WEEKEND. A SYSTEM OF INTEREST IS
HURRICANE TEDDY...FORECAST TO AVOID THE CARIBBEAN. HOWEVER...TEDDY
IS A LARGE SYSTEM AND IS FORECAST TO DRAW THE ITCZ
NORTHWARD...WHICH WILL RESULT IN MODERATE PRECIPITATION IN THE
WINDWARD ISLANDS LATE ON FRIDAY AND ON SATURDAY...AND IN THE
FRENCH ANTILLES ON SATURDAY...AND LEEWARD ISLANDS ON SUNDAY.
FURTHERMORE...TEDDY IS STEERING THE REMNANTS OF ONCE TROPICAL
CYCLONE RENE INTO THE NORTHEAST CARIBBEAN...TO STIMULATE
PRECIPITATION IN THE LEEWARD ISLANDS...VIRGIN ISLANDS AND PUERTO
RICO ON THURSDAY. IN TERMS OF RAINFALL ACCUMULATIONS...ON
THURSDAY...EXPECTING THE REMNANTS OF RENE TO SUSTAIN 05-10MM/DAY
AND MAXIMA OF 15-25MM IN THE LEEWARD ISLANDS...PUERTO RICO AND THE
VIRGIN ISLANDS. ALSO ON THURSDAY...A TROUGH IN THE TRADES WILL
ENHANCE CONVECTION IN THE SOUTHEAST BAHAMAS/SOUTHEAST CUBA AND
JAMAICA...TO SUSTAIN 05-10MM/DAY AND MAXIMA OF 15-25MM IN JAMAICA
AND SOUTHEAST CUBA...AND MAXIMA OF 15MM IN THE SOUTHEAST BAHAMAS
AND TURKS AND CAICOS. ON FRIDAY...LARGEST ACCUMULATIONS ARE
EXPECTED IN THE SOUTHERN WINDWARD ISLANDS...WHERE THE ITCZ
MODULATED BY TEDDY WILL FAVOR 15-20MM/DAY AND MAXIMA OF 25-50MM.
IN HAITI AND EASTERN CUBA...DIURNAL CONVECTION WILL FAVOR
05-10MM/DAY AND MAXIMA OF 15-25MM...WHILE IN PUERTO RICO AND THE
EASTERN DOMINICA REPUBLIC EXPECTING ISOLATED MAXIMA OF 15MM. ON
SATURDAY...EXPECTING SCATTERED ACCUMULATIONS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM IN THE CENTRAL LESSER ANTILLES...WHILE DIURNAL
CONVECTION IN PUERTO RICO AND THE DOMINICAN REPUBLIC FAVORS
05-10MM/DAY AND MAXIMA OF 15-25MM. IN THE NORTHWEST BAHAMAS...A
PRE-FRONTAL TROUGH STRUCTURE WILL FAVOR 05-10MM/DAY AND MAXIMA OF
15-20MM. SIMILAR AMOUNTS ARE EXPECTED IN CENTRAL AND WESTERN
CUBA...WHILE ISOLATED CONVECTION AND LIGHT ACCUMULATIONS PREVAIL
IN JAMAICA AND SOUTHEAST CUBA.

IN CENTRAL AMERICA AND AT UPPER LEVELS...A WEAK TUTT IS MOVING
WESTWARD ACROSS NICARAGUA/HONDURAS/EL SALVADOR ON
THURSDAY...GUATEMALA ON FRIDAY...TO THEN EXIT INTO THE PACIIC. THE
TUTT WILL PROVIDE SOME ENHANCEMENT OF DIURNAL CONVECTION IN
COMBINATION WITH A TROPICAL WAVE PROPAGATINC ACROSS EL
SALVADOR/WESTERN HONDURAS AND GUATEMALA ON THURSDAY. THIS WILL
FAVOR ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF 20-40MM IN THESE
REGIONS...WHILE DIURNAL CONVECTION IN NICARAGUA...HONDURAS AND THE
GULF OF FONSECA REGION FAVORS 05-10MM/DAY AND MAXIMA OF 15-30MM.
EXPECTING A DECREASE IN ACTIVITY AFTERWARDS AS BOTH TROPICAL WAVE
AND TUTT MOVE AWAY FROM THE REGION. ON FRIDAY...THIS WILL FAVOR
05-10MM/DAY AND MAXIMA OF 15-30MM FROM HONDURAS/EL SALVADOR AND
AREAS TO THE NORTHWEST. IN NICARAGUA AND EASTERN HONDURAS
EXPECTING A DECREASE T0 05-10MM/DAY AND MAXIMA OF 15-20MM. ON
SATURDAY...EXPECT ACCUMULATIONS OF 10-15M/DAY AND MAXIMA OF
20-35MM IN WESTERN HONDURAS...EL SALVADOR AND GUATEMALA...WHILE IN
NICARAGUA EXPECT MAXIMA OF 15-25MM.

A WETTER PATTERN IS EXPECTED IN SOUTHERN CENTRAL AMERICA IN
ASSOCIATION WITH AN ACTIVE ITCZ...AND SOUTHWESTERLY WINDS
INTERACTING WITH THE MOUNTAINS OF COSTA RICA AND WESTERN PANAMA.
THIS WILL SUSTAIN 15-20MM/DAY AND MAXIMA OF 25-50MM ON THURSDAY
AND FRIDAY. ON SATURDAY..EXPECTING SCATTERED ACCUMULATIONS OF
10-15MM/DAY AND MAXIMA OF 20-40MM IN SOUTHERN COSTA RICA AND
PANAMA...ALTHOUGH ISOLATED LARGER AMOUNTS ARE POSSIBLE IN PANAMA.

IN NORTHERN SOUTH AMERICA...EXPECTING A GRADUAL RELOCATION OF
STRONGEST CONVECTION FROM EAST TO WEST THROUGH THE CYCLE. IN THE
UPPER LEVELS...DIFFLUENT EASTERLY FLOW WILL PROVIDE VENTILATION ON
A DAILY BASIS. BUT THE INTERACTION BETWEEN TROPICAL CYCLONE TEDDY
IN THE ATLANTIC AND THE ITCZ/NET WILL MODULATE THE REGIONS OF
STRONGEST CONVECTION. ANOTHER ACTIVE REGION WILL BE SOUTHWEST
COLOMBIA...WHERE MOIST ONSHORE FLOW WILL FAVOT MODERATE
PRECIPITATION THROUGH THE CYCLE. ON THURSDAY...CONVECTION ALONG
THE NET WILL SUSTIN 05-10MM/DAY AND MAXIMA OF 15-30MM IN NORTHERN
GUYANA AND SOUTHEAST/CENTRAL VENEZUELA...WHILE IN NORTHWEST
VENEZUELA AND WESTERN COLOMBIA EXPECTING 10-15MM/DAY AND MAXIMA OF
20-40MM. ON FRIDAY...EXPECTING A PEAK IN ACTIVITY IN EASTERN
VENEZUELA IN ASSOCIATION WITH TEDDY...TO FAVOR 15-20MM/DAY AND
MAXIMA OF 25-50MM. IN WESTERN VENEZUELA AND CENTRAL AND WESTERN
COLOMBIA EXPECTING 10-15MM/DAY AND MAXIMA OF 20-40MM. ON
SATURDAY...LARGEST AMOUNTS ARE EXPECTED IN NORTHWEST VENEZUELA AND
NORTHERN COLOMBIA TO REACH 15-20MM/DAY AND MAXIMA OF 35-70MM. IN
WESTERN COLOMBIA EXPECTING MAXIMA OF 20-40MM. IN EASTERN
VENEZUELA...EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM.

TROPICAL WAVES/TUTT INDUCED PERTURBATIONS/TRADE WIND SURGES
TYPE  17/12  18/00  18/12  19/00  19/12  20/00  20/12  21/00 SOF
TW      86W    90W    93W    97W    99W   102W   104W   107W 22N
TW     102W   104W   106W   108W   110W   113W   116W   119W 25N

A TROPICAL WAVE IS PROPAGATING ACROSS WESTERN CENTRAL AMERICA...TO
SUSTAIN MAXIMA OF 20-40MM IN WESTERN EL SALVADOR...GUATEMALA AND
CHIAPAS ON THURSDAY...AND MAXIMA OF 15-25MM IN THE YUCATAN
PENINSULA. ON FRIDAY...THIS WILL FAVOR MAXIMA OF 25-50MM IN
SOUTHERN MEXICO...WHILE ON SATURDAY THIS FAVORS MAXIMA OF 20-40MM
IN MOST OF SOUTHERN MEXICO.

ANOTHER TROPICAL WAVE IS INITIALIZED AT 102W AND WILL ENHANCE
CONVECTION IN WESTERN MEXICO ON THURSDAY TO FAVOR MAXIMA OF
25-50MM.

GALVEZ/DAVISON...WPC (USA)