TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
138 PM EDT TUE MAY 05 2009
 
DISCUSSION FROM MAY 05/0000 UTC. ON THE NORTHERN STREAM... THE
GLOBAL AND REGIONAL MODELS INITIALIZE A BROAD/LOW AMPLITUDE TROUGH
THAT EXTENDS ACROSS THE USA TO THE WESTERN ATLANTIC. MID/UPPER
LEVEL PERTURBATIONS EMBEDDED IN THIS FLOW...WITH ONE TO EJECT
ACROSS THE EASTERN USA EARLY THIS PERIOD WHILE ANOTHER CLEARS THE
EAST COAST BY 60 HRS. AS THEY CLEAR THE EASTERN SEABOARD...THE
FLOW SPLITS WITH SOME OF THE ENERGY LIFTING NORTHEASTWARD INTO THE
NORTH ATLANTIC WHILE SOME SHEARS SOUTHEASTWARD ACROSS THE
BAHAMAS-NORTH OF THE GREATER ANTILLES. THESE VORTICES THEN REVOLVE
AROUND A WANING TROUGH NORTH OF THE ISLANDS. THE WANING TROUGH
EXTENDS SOUTH FROM A LOW NORTH OF THE TURKS AND CAICOS TO JUST
NORTH OF LA GUAJIRA PENINSULA IN NORTHERN COLOMBIA. THE TROUGH
NORTH OF THE ISLANDS...HOWEVER...TENDS TO WEAKEN/FILL TOWARDS THE
END OF THE PERIOD. AT UPPER LEVELS...AS THE TROUGH WEAKENS AND THE
GRADIENT SLACKENS...A SUBTROPICAL JET OVER AND NORTH OF THE
ISLANDS IS ALSO FORECAST TO WEAKEN. AS EVIDENT ON THE IMAGERY...
CURRENT DYNAMICS ARE NOT AS STRONG AS THEY WERE  YESTERDAY...AND
THE TENDENCY IS FOR PATTERN TO GRADUALLY WEAKEN.

THE MID LEVEL LOW...MEANWHILE...FAVORS GENERATION OF SHORT WAVE
PERTURBATIONS IN-SITU...WITH WAVES/INVERTED TROUGHS FORMING OVER
THE ISLAND CHAIN AND WANING AS THEY ENTER THE CENTRAL/SOUTHERN
CARIBBEAN. ONE EXTENDS FROM NORTHERN COLOMBIA TO SOUTH OF HAITI
ALONG 74W...WHILE ANOTHER EXTENDS ACROSS THE VIRGIN ISLES/EASTERN
PUERTO RICO. THE FIRST MOVES TO GULF OF URABA/DARIEN IN PANAMA BY
30-36 HRS...WHERE IT IS FORECAST TO QUICKLY DAMPEN. THE SECOND...
CROSSES THE MONA PASSAGE TO EASTERN HISPANIOLA BY 30-36
HRS...CROSSING 71W/72W BY 48 HRS...74W BY 60 HRS...AND DISSIPATING
OVER THE SOUTHERN CARIBBEAN BY 66-72 HRS. BEST MOIST FLUX
CONVERGENCE IS EXPECTED ACROSS THE FRENCH/ LEEWARD ISLANDS...TO
THE VIRGIN ISLES-PUERTO RICO AND PORTIONS OF THE DOMINICAN
REPUBLIC. BUT AS UPPER DYNAMICS WANE...THE GENERAL TENDENCY IS FOR
CONVECTIVE ACTIVITY TO ALSO WANE. MOST ACTIVE CONVECTION IS NOW
EXPECTED BETWEEN 18-54 HRS...WITH A GRADUAL DECREASE THROUGH 72-84
HRS. OVER HISPANIOLA EXPECT ACCUMULATION OF 10-15MM/DAY AND MAXIMA
OF 25-50MM ON DAY 01...WHILE ON DAY 02 THE MAXIMA WILL PEAK AT
20-40MM. ON DAY 03 RAINFALL AMOUNTS WILL DECREASE TO 05-10MM/DAY
AND THE MAXIMA TO 15-30MM. ACROSS PUERTO RICO-VIRGIN ISLANDS
EXPECT ACCUMULATION OF 10-20MM/DAY AND MAXIMA OF 30-60MM THROUGH
36 HRS...TO INCREASE TO 35-70MM BY 36-54 HRS. AT 60-84 HRS MAXIMA
WILL PEAK AT 20-35MM/DAY. OVER THE FRENCH-LEEWARD ISLANDS EXPECT
RAINFALL ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-40MM THROUGH
36 HRS...SURGING TO 25-50MM AT 36-60 HRS...THEN SETTLE AT
10-15MM/DAY BY 60-84 HRS. CONVECTION IS ALSO EXPECTED ACROSS THE
ABC ISLANDS ON DAY 01...WITH ACCUMULATION OF 00-05MM/DAY AND
MAXIMA OF 10MM.

A TUTT OVER THE EASTERN PACIFIC ORIGINATES ON A CLOSED LOW NEAR
14N 106W. UNDER INFLUENCE OF A RIDGE TO THE NORTH... THE TUTT LOW
IS FORECAST TO RETROGRESS ALONG 13N 110W BY 48 HRS...AND WEST OF
110W BY 54-60 HRS. BUT AS IT PULLS AWAY...A TROUGH OVER NORTH
AMERICA IS TO AMPLIFY ACROSS THE GULF TO THE YUCATAN/CAMPECHE
SOUND BY 54-60 HRS...WITH AXIS TO EXPAND ACROSS SOUTHERN
FLORIDA/KEYS-WESTERN CUBA TO THE YUCATAN BY 72-84 HRS. THIS WILL
HAVE AN IMPACT ON DIURNAL CONVECTION ALONG THE CONTINENTAL DIVIDE
FROM SOUTHERN CHIAPAS MEXICO TO NORTHERN EL SALVADOR/SOUTHERN
HONDURAS. IN THIS AREA EXPECT RAINFALL AMOUNTS OF
05-10MM/DAY...WITH MAXIMA OF 20-40MM/DAY ON DAY 01...15-30MM ON
DAY 02...AND 25-50MM/DAY ON DAY 03. 

ALSO AT UPPER LEVELS...THE SUBEQUATORIAL RIDGE REMAINS FROM
WEST-TO-EAST FROM THE TROPICAL ATLANTIC...ACROSS NORTHERN SOUTH
AMERICA TO THE EASTERN TROPICAL PACIFIC ALONG 05N. THIS PATTERN
WILL PERSIST THROUGH DAY 03. INITIALLY TWO HIGHS WILL ANCHOR THIS
AXIS...ONE OVER PANAMA/GULF OF URABA REGION AND THE OTHER OVER THE
ATLANTIC NEAR 10N 25W. UNDER INFLUENCE OF THIS RIDGE...AND THE
TUTT TO THE WEST...THE ITCZ OVER THE PACIFIC MEANDERS ALONG
07N/08N TO SOUTHERN CENTRAL AMERICA-NORTHWEST COLOMBIA. AS THE
CONVERGENCE ZONE  MEANDERS INTO SOUTHERN CENTRAL AMERICA...IT IS
TO CONTINUE FAVORING PERIODS OF MODERATE TO HEAVY RAINS OVER COSTA
RICA-PANAMA...WHERE WE EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 20-40MM/DAY. OVER EJE CAFETERO TO NORTHERN COLOMBIA...TO
ALSO AFFECT SANTANDERES AND LAKE MARACAIBO REGION IN NORTHWEST
VENEZUELA...EXPECT RAINFALL AMOUNTS OF 10-20MM/DAY AND MAXIMA OF
25-50MM/DAY ON DAY 01...TO DECREASE TO 20-40MM/DAY ON DAYS 02-03.
NOTE THAT LOCALLY HIGHER AMOUNTS ARE POSSIBLE OVER SANTANDERES/
NORTHERN BORDER WITH VENEZUELA. INLAND ALONG THE NEAR EQUATORIAL
TROUGH...DAILY MAXIMA IS TO ALSO PEAK AT 20-40MM/DAY OVER AMAZONIA
IN SOUTHERN VENEZUELA TO AMAZONIA/ PIEDEMONTE LLANERO IN SOUTHERN
COLOMBIA. 

THE GUIANAS ARE ALSO UNDER INFLUENCE OF THE SUBEQUATORIAL RIDGE AT
UPPER LEVELS. IN THIS AREA THE MODELS SHOW A MOIST SURGE TO START
OVER FRENCH GUIANA BY 30-36 HRS...TO EXPAND OVER SURINAME BY 36-42
HRS...AND NORTHERN GUYANA/ORINOCO DELTA REGION-SOUTHERN WINDWARD
ISLANDS BY 48-60 HRS. MEANWHILE...EXPECT RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA OF 10-20MM. THIS INCREASES TO 10-15MM/DAY
AND MAXIMA OF 20-40MM OVER FRENCH GUIANA BY 36-48 HRS...WHILE OVER
SURINAME TO GUYANA WE EXPECT ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15-30MM. CONVECTION IS TO ALSO EXPAND TO THE SOUTHERN
WINDWARD ISLANDS/GRENADINES BY 54-60 HRS...WITH SIMILAR AMOUNTS.

ALVARADO...ETESA (PANAMA)
GONZALEZ...IDEAM (COLOMBIA) 
DAVISON...NCEP  (USA)