Prognostic Meteorological Discussion
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FXCA20 KWBC 241831
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 PM EDT WED MAY 24 2017

TROPICAL DISCUSSION FROM MAY 24/12 UTC: DEEP POLAR TROUGH
AMPLIFIES ACROSS THE MISSISSIPPI VALLEY IN THE USA TO THE CENTRAL
GULF OF MEXICO LATER THIS AFTERNOON. ON THURSDAY THE BASE OF THE
TROUGH STARTS TO PULL AS THE TROUGH BEGINS TO LIFT OVER A BROAD
RIDGE TO THE EAST. AS THE TROUGH LIFTS...ASSOCIATED SURFACE FRONT
WILL LOSE ITS UPPER LEVEL SUPPORT AND IT IS FORECAST TO FRONTOLIZE
ON FRIDAY TO SATURDAY. MEANWHILE...THE FRONT WILL MOVE ACROSS
CENTRAL FLORIDA-THE GULF TO VERACRUZ MEXICO LATER TODAY. THE
FRONTAL BOUNDARY IS TO THEN MEANDER ACROSS THE NORTHWEST BAHAMAS
ON THURSDAY... WHILE TRAILING END OVER THE GULF STARTS TO
WEAKEN/FRONTOLIZE. PREFRONTAL CONVECTION ACROSS VERACRUZ-CENTRAL
MEXICO IS TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF
20-40MM THROUGH THURSDAY MORNING. OVER THE NORTHWEST
BAHAMAS...PREFRONTAL CONVECTION LATER TODAY WILL RESULT IN
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ON THURSDAY
THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-35MM...WANING ON
FRIDAY. ALSO...PREFRONTAL CONVECTION OVER WESTERN CUBA/ISLAND OF
YOUTH WILL RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15MM. FURTHERMORE...AS IT MEANDERS OVER THE GULF EARLY IN THE
CYCLE...THE POLAR FRONT WILL INDUCE A PREFRONTAL TROUGH ACROSS THE
YUCATAN PENINSULA. THE TROUGH WILL ENHANCE LOW LEVEL MOISTURE
CONVERGENCE ACROSS THE PENINSULA TO TRIGGER RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15MM.

THE DEEP POLAR TROUGH...AS IT MEANDERS OVER THE GULF...WILL FAVOR
A CONVECTIVELY UNSTABLE AIR MASS ACROSS THE SOUTHERN STATES OF
MEXICO AND NORTHERN CENTRAL AMERICA. ALTHOUGH THE POLAR TROUGH
LIFTS ACROSS THE EASTERN USA...THE FAVORABLE ENVIRONMENTAL
CONDITIONS ARE FORECAST TO PERSIST DURING THE NEXT 72-96 HRS.
ACROSS SOUTHERN MEXICO-GUATEMALA TO SOUTHERN HONDURAS/EL SALVADOR
CONVECTION IS TO CLUSTER ALONG THE CONTINENTAL DIVIDE...MEANWHILE
TRIGGERING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM.
PEAK IN ACTIVITY IS EXPECTED ON FRIDAY...WITH RAINFALL AMOUNTS OF
15-20MM/DAY AND MAXIMA OF 30-60MM TO CLUSTER BETWEEN SOUTHERN
CHIAPAS IN MEXICO TO EL SALVADOR/GULF OF FONSECA. OVER EASTERN
NICARAGUA/NORTHEAST HONDURAS EXPECTING RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10MM...INCREASING TO 05-10MM/DAY AND
MAXIMA OF 15-25MM ON THURSDAY. OVER SOUTHERN NICARAGUA-COSTA RICA
AND WESTERN PANAMA EXPECT RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA 20-40MM. ON FRIDAY THIS INCREASES TO 15-20MM/DAY AND MAXIMA
OF 30-60MM.

DOWNSTREAM FROM THE CONTINENTAL TROUGH...A MID LEVEL RIDGE EXTENDS
FROM THE CENTRAL/EASTERN CARIBBEAN TO THE WESTERN ATLANTIC...WHILE
ANCHORING ON A CLOSED HIGH OVER EASTERN HISPANIOLA/PUERTO RICO. AS
THE TROUGH LIFTS OVER THIS RIDGE ON THURSDAY-FRIDAY THE RIDGE
TENDS TO FLATTEN TO THE NORTH OF 28N/30N. ALTHOUGH THE RIDGE TENDS
TO WEAKEN...ASSOCIATED TRADE WINDS CAP IS EXPECTED TO HOLD DURING
THE NEXT 60-72 HRS. MEANWHILE...THIS IS TO FAVOR FAIR WEATHER
CONDITIONS ACROSS PORTIONS OF HISPANIOLA-PUERTO RICO-VIRGIN ISLES
AND THE ISLAND CHAIN. AT LOW LEVELS...THE RIDGE ALOFT SUSTAINS A
BROAD RIDGE OVER THE CENTRAL/WESTERN ATLANTIC THAT CENTERS ON A
CLOSED HIGH TO THE SOUTHEAST OF BERMUDA. THE RIDGE SUSTAINS A
TIGHT GRADIENT ACROSS THE EASTERN-CENTRAL CARIBBEAN...WITH 850 HPA
WINDS OF 25-35KT. UNDER PRESSURE FROM THE POLAR TROUGH/FRONT
EXITING THE EASTERN USA THE RIDGE TENDS TO WEAKEN LATER ON
THURSDAY. AS THE GRADIENT SLACKENS WINDS ACROSS THE BASIN WILL
DECREASE TO 15-25KT LATER ON FRIDAY.

AS THE MID LEVEL RIDGE MEANDERS OVER THE WESTERN ATLANTIC...IT IS
TO INDUCE THE SOUTHWARD AMPLIFICATION OF A TUTT EAST OF THE
ISLANDS LATER ON WEDNESDAY/EARLY ON THURSDAY. AT 500 HPA THE TUTT
EVOLVES INTO A CLOSED LOW EAST OF THE LEEWARD ISLES LATER ON
THURSDAY. THE TUTT LOW WILL THEN REMAIN NEARLY STATIONARY THROUGH
SATURDAY EVENING/SUNDAY MORNING. AS THE TUTT PRESSES AGAINST THE
RIDGE TO THE WEST...THE TRADE WINDS CAP RELAXES ITS FOOTHOLD
ACROSS THE NORTHEAST CARIBBEAN ISLES. THIS WILL ALLOW FOR AN
INCREASE IN CONVECTIVE INSTABILITY/SHALLOW MOISTURE POOLING ACROSS
THE LEEWARD ISLES ON THURSDAY TO FRIDAY...THAT SPREADS ACROSS THE
VIRGIN ISLES TO PUERTO RICO ON FRIDAY TO SATURDAY. IN
RESPONSE...THE GFS AND ECMWF BOTH SHOW AN INCREASE IN CONVECTION
BETWEEN THE LEEWARD ISLES AND PUERTO RICO...WITH ACCUMULATION OF
00-05MM/DAY AND ISOLATED MAXIMA OF 10MM OVER THE LEEWARD ISLES ON
THURSDAY TO SATURDAY...WITH SIMILAR AMOUNTS OVER PUERTO RICO ON
FRIDAY TO SATURDAY.

ITCZ RELATED CONVERGENCE OVER THE NORTHERN GUIANAS WILL FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH
FRIDAY IT WEAKENS TO 05-10MM/DAY AND MAXIMA OF 15-25MM. OVER
VENEZUELA AND EASTERN COLOMBIA INITIALLY EXPECTING RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-45MM...WITH MOST ACTIVE
ALONG THE NEAR EQUATORIAL TROUGH TO THE SOUTH. THROUGH THURSDAY
THIS DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-30MM. OVER WESTERN
COLOMBIA INITIALLY EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-40MM. THROUGH FRIDAY IT INCREASES TO 15-20MM/DAY AND
MAXIMA OF 30-60MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24     36     48     60     72     84     96       TYPE
35W      38W    42W    45W    47W    50W    53W     56W      TW
55W      58W    60W    62W    65W    67W    DISSIPATES       TW
72W      74W    76W    78W    81W    83W    85W     87W      EW
82W      84W    86W    87W    89W    91W    93W     94W      EW

TROPICAL WAVE IS INITIALIZED ALONG 35W AND TO THE SOUTH OF 13N.
THIS ENTERS EASTERN GUYANA LATER ON FRIDAY...TO FAVOR RAINFALL
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.

TROPICAL WAVE ALONG 55W AND SOUTH OF 08N CROSSES SURINAME TO
GUYANA EARLY ON THURSDAY. MEANWHILE...AS IT INTERACTS WITH THE
ATLANTIC ITCZ IT IS TO TRIGGER SCATTERED COASTAL CONVECTION WITH
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ON THURSDAY THE
MAXIMA INCREASES TO 20-40MM. ACROSS VENEZUELA TO EASTERN COLOMBIA
THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA
OF 20-35MM ON THURSDAY TO SATURDAY MORNING.

AN EASTERLY WAVE IS INITIALIZED ALONG 72W AND TO THE SOUTH OF 11N.
THIS IS INTERACTING WITH THE NEAR EQUATORIAL TROUGH OVER WESTERN
VENEZUELA/EASTERN COLOMBIA TO TRIGGER RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-45MM THROUGH THURSDAY MORNING. THIS
IS ALSO INDUCING A MOIST PLUME ALONG THE SOUTHERN FRINGES OF THE
SUBTROPICAL RIDGE TO THE NORTH THAT ADVECTS ACROSS JAMAICA LATER
TODAY...WHERE IT IS TO TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15-20MM. ON THURSDAY IT IS TO INTERACT WITH THE EASTERN
PACIFIC ITCZ AS IT MOVES ACROSS WESTERN COLOMBIA/THE DARIEN IN
EASTERN PANAMA TO TRIGGER RAINFALL AMOUNTS OF 15-20MM/DAY AND
MAXIMA OF 30-60MM. ACROSS COSTA RICA/WESTERN PANAMA AND SOUTHERN
NICARAGUA IT IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-45MM ON FRIDAY TO SATURDAY.

TROPICAL WAVE ALONG 82W AND TO THE SOUTH OF 12N ENHANCES
CONVECTION ACROSS COSTA RICA/SOUTHERN NICARAGUA TO FAVOR RAINFALL
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. ON THURSDAY IT IS TO
THEN ENHANCE CONVECTION ACROSS THE GULF OF FONSECA/SOUTHERN
NICARAGUA-EL SALVADOR...TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY
AND MAXIMA OF 20-45MM. ON FRIDAY THIS INCREASES TO 15-20MM/DAY AND
MAXIMA OF 30-60MM WHILE SPREADING WEST ACROSS EL SALVADOR TO
SOUTHERN GUATEMALA.

GAJADHAR...SLMS (SAINT LUCIA)
SUBRATH-ALI...TTMS (TRINIDAD AND TOBAGO)
DAVISON/GALVEZ...WPC (USA)
$$





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