000 
FXCA20 KWBC 201747
PMDCA 
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
146 PM EDT THU MAY 20 2004
 
DISCUSSION VALID FROM MAY 20/0000 UTC...

A WELL DEFINED BROAD MID/UPPER LEVEL TROUGH WITH AXIS
ORIENTATED NORTHEAST-SOUTHWEST ACROSS THE SOUTHERN CARIBBEAN
SEA-SOUTHERN NICARAGUA AND THE EASTERN PACIFIC AT 24-30HRS
WILL DRIFT SLOWLY NORTHWARD TO REACH JUST SOUTH OF
HISPANIOLA-JAMAICA BY 72HRS. AT 850 HPA... HUGGING THE AXIS
OF THE TROUGH ARE TWO CYCLONIC CENTERS... LOCATED NEAR 10N
88W AND 15N 70W RESPECTIVELY. NOTE... THIS IS A LITTLE
SLOWER THAN PREVIOUSLY FORECAST. THE CYCLONIC TURNING
ASSOCIATED WITH BOTH CENTERS AS WELL AS THE WELL DEFINED
AXIS OF THE TROUGH IS QUITE EVIDENT ON SATELLITE IMAGERY.
THE MODELS REMAIN IN AGREEMENT WITH THE NORTHWARD MOTION OF
THE TROUGH AXIS THROUGH 72-84HRS. THE AXIS OF THE TROUGH AT
500 HPA FOLLOWS A VERY SIMILAR PATTERN AS DOES THE
POSITIONING OF THE CYCLONIC CENTERS. 

AN ELONGATED MID/UPPER LEVEL TROUGH WILL REMAIN STATIONARY
ACROSS THE SOUTHWEST ATLANTIC-NORTHERN BAHAMAS-SOUTHERN
FLORIDA WITH THE BASE TRAILING ACROSS THE EASTERN GULF OF
MEXICO-YUCATAN TO SOUTHERN GUATEMALA THROUGH 48-54HRS. AT
500 HPA THE ELONGATED TROUGH AXIS IS SUPPORTED BY A CYCLONIC
CENTER NEAR 23N 90W THROUGH 24-36HRS... HEREAFTER TO DRIFT
EAST TO 23N 81W BY 60-72HRS. PROPAGATING TO THE RIGHT OF
THIS TROUGH AXIS... OVER THE CENTRAL/SE BAHAMAS AND NORTH OF
THE LEEWARD ISLES IS A SUBTROPICAL JET WITH WINDS IN EXCESS
OF 60-90KTS. A BROAD AREA OF CYCLONIC FLOW DOMINATES MOST OF
THE CARIBBEAN-CENTRAL AMERICA THROUGH 60-72HRS WHICH WILL
HELP TO PROVIDE GOOD OUTFLOW OVER THE LOW-MID LEVEL
TROUGH... THE ETA MODEL IS ALSO SHOWING A FAIRLY GOOD AREA
OF UPPER LEVEL DIVERGENCE OVER NICARAGUA/HONDURAS DURING THE
NEXT 30-48HRS. THEREFORE... THE CARIBBEAN PLAINS OF
NICARAGUA-COSTA RICA AND EASTERN HONDURAS CAN EXPECT
RAINFALL ACCUMULATION OF 35-50MM/DAY AND MAXIMA OF 75-125MM.
OVER BELIZE-EL SALVADOR AND YUCATAN EXPECT RAINFALL AMOUNTS
OF 05-15MM/DAY WHILE OVER GUATEMALA EXPECT RAINFALL
ACCUMULATION OF 15-30MM/DAY AND MAXIMA OF 50-75MM. WITH MOST
OF THE ENERGY LIFTING SLOWLY NORTHWARD WITH THE TROUGH...
PANAMA- WESTERN/NORTHERN COLOMBIA CAN EXPECT RAINFALL
ACCUMULATION OF 10-25MM/DAY AND MAXIMA OF 30-60MM TO
CONCENTRATE OVER NORTHWESTERN COLOMBIA.  
     
UPSTREAM OF THE AFOREMENTIONED ELONGATED TROUGH... A
MID/UPPER LEVEL RIDGE CONTINUES TO BUILD OVER THE CENTRAL US
AND INTO SOUTHWEST MEXICO. THIS RIDGE IS BEING SUPPORTED BY
A NEARLY STACKED STATIONARY HIGH LOCATED ALONG 25N 104W
THROUGH 72HRS. THE RIDGE WILL HELP TO PRODUCE A MORE
SUBSIDENT(DRYING) PATTERN OVER CENTRAL-EASTERN MEXICO
THROUGH 72HRS... TO RESULT IN SHALLOW CONVECTION OVER
SOUTHERN MEXICO/MEXICO CITY-DF WITH RAINFALL ACCUMULATION OF
10-20MM/DAY AND MAXIMA OF 35MM MAINLY OVER CHIAPAS AND
OAXACA TO PEAK IN A DIURNAL PATTERN. 

AT 850 HPA A BROAD ANTICYCLONIC CENTER DOMINATES THE
SOUTHEAST US-WESTERN ATLANTIC AND CARIBBEAN BASIN THROUGH
THE ENTIRE CYCLE. THE CENTER WHICH IS LOCATED NEAR 32 86W
THROUGH 24-30 HRS WILL DRIFT TO 30N 70W BY 60-72HRS. THIS
WILL RESULT IN A LIGHT TO MODERATE EASTERLY FLOW OVER THE
AFOREMENTIONED REGION THROUGH THE CYCLE. HOWEVER... AS THE
BEFORE MENTIONED LOW/MID LEVEL TROUGH DRIFTS NORTHWARD...
THE EASTERLY FLOW OVER CENTRAL AMERICA-WESTERN CARIBBEAN
WILL BECOME MORE NORTHEAST THROUGH 48-72HRS... WHILE
BECOMING MORE SOUTHEAST OVER THE WINDWARD ISLES. THIS
NORTHEAST FLOW ACROSS THE CARIBBEAN PLAINS OF CENTRAL
AMERICA WILL HELP TO SUSTAINED SCATTERED CONVECTION THROUGH
MOST OF THE CYCLE. OVER JAMAICA-HISPANIOLA-CAYMAN ISLES AND
PUERTO RICO EXPECT ISOLATED TO SCATTERED CONVECTION THROUGH
48 HRS WITH RAINFALL ACCUMULATION OF 05-15MM/DAY AND
ISOLATED MAXIMA OF 25MM. HOWEVER... AS THE TROUGH MOVES
FURTHER NORTH... THIS WILL RESULT IN DEEP/ SCATTERED
CONVECTION LATER THIS CYCLE. THE VIRGIN/LEEWARD ISLES WILL
CONTINUE TO RECEIVE WIDELY SCATTERED CONVECTION THROUGH 54-
60HRS AS THE SUBTROPICAL JET MEANDERS NORTH OF THE ISLANDS.
THIS WILL RESULT IN RAINFALL ACCUMULATION OF 15-30MM/DAY
OVER THE LEEWARD/VIRGIN ISLES WITH MAXIMA OF 50MM MAINLY
OVER THE FRENCH ISLES.

THE SUB-EQUATORIAL RIDGE IS TO CONTINUE MEANDERING ALONG 11N
AT 250 HPA THROUGH 72 HRS. SUPPORTED THIS RIDGE IS A SERIES
OF ANTICYCLONIC CENTERS EAST OF THE SOUTHERN WINDWARD ISLES
NEAR 11N 47W AND 11N 25W RESPECTIVELY. AS THE CENTER ALONG
47W NORTH OF 10N STRENGTHENS AND DRIFTS WEST THROUGH 48-54
HRS... IT WILL BUILD A RIDGE NORTH ALONG 67W/68W THROUGH
72HRS. THIS BUILDING RIDGE WILL SPLIT THE AFOREMENTIONED
ELONGATED TROUGH LOCATED NORTH OF THE ISLANDS. THIS WILL
FORCE THE AXIS OF THE LOW/MID LEVEL TROUGH IN THE
CENTRAL/SOUTHERN CARIBBEAN SEA TO BECOME MORE SOUTHEAST TO
NORTHEAST ORIENTATED. THE MAIN AXIS OF THE SUB-EQUATORIAL
RIDGE WILL CONTINUE TO EXTEND WESTWARD ACROSS NORTHERN SOUTH
AMERICA TO THE EASTERN PACIFIC THROUGH 60-72HRS. AT 500 HPA.
.. THE RIDGE EXTENDS E-W ACROSS THE SOUTHERN ATLANTIC-
NORTHERN SOUTH AMERICA THROUGH 72HRS. THE BROAD AXIS OF THIS
RIDGE WILL CONTINUE TO SUPPORT UPPER LEVEL DIFFLUENCE OVER
NORTHERN VENEZUELA-SOUTHERN WINDWARD THROUGH 72HRS. EARLY
THIS CYCLE AS THE LOW-MID LEVEL TROUGH REMAINS NEARLY
STATIONARY NORTH OF THE NETHERLANDS ANTILLES(ABC ISLES)/LAKE
MARACAIBO... ALONG WITH THE UPPER LEVEL DIFFLUENCE OVER
NORTHERN VENEZUELA... THIS WILL RESULT IN RAINFALL
ACCUMULATION OF 10-20MM/DAY OVER ABC/NORTHERN VENEZUELA AND
MAXIMA OF 40MM TO CONCENTRATE OVER LAKE MARACAIBO. OVER
SOUTHERN VENEZUELA/COLOMBIA EXPECT RAINFALL AMOUNTS OF 15-
30MM/DAY AND MAXIMA OF 50-75MM OVER SOUTHERN COLOMBIA. WITH
MOST OF THE MOISTURE MOVING NORTH EARLY THIS CYCLE... THIS
WILL RESULT IN ISOLATED TO SCATTERED CONVECTION OVER THE
GUIANAS... TO RESULT IN RAINFALL ACCUMULATION OF 10-25MM/DAY
WITH MAXIMA OF 45MM OVER GUYANA. THE SOUTHERN WINDWARD ISLES
CAN EXPECT RAINFALL AMOUNTS OF 10-20MM/DAY.

GUERRERO.......ONAMET (REPUBLICA DOMINICANA)
MOXEY-BONAMY...NWS (THE BAHAMAS)
CARR...........NCEP (HPC)


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