FXCA20 KWBC 181846
PMDCA 
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
145 PM EST FRI FEB 18 2005
 
DISCUSSION FROM FEB 18/0000UTC...THE UPPER FLOW AT 
250 HPA SPLITS BETWEEN A RIDGE OVER THE GULF/ 
SOUTHERN USA...AND A CROSS EQUATORIAL TROUGH OVER 
THE EASTERN PACIFIC EXTENDING TO THE COAST OF 
COLOMBIA-ECUADOR/NORTHERN PERU. THE TROUGH WILL 
INITIALLY CENTER ON A CLOSED LOW NEAR 10N 95W... 
THAT FILLS TO AN OPEN TROUGH BY 60-72 HRS. THE 
TROUGH WILL SUPPORT DIVERGENCE ALOFT ACROSS 
SOUTHERN COLOMBIA...WHERE IT WILL VENT CONVECTION. 
SHORT WAVE VORTICES WILL LIFT OVER THE RIDGE...TO 
STREAK ACROSS EXTREME NORTHERN BAJA-SONORA IN 
MEXICO...MEANWHILE TRIGGERING LIGHT CONVECTION 
WITH ACCUMULATION OF 05-10MM/DAY AT 42-72 HRS. 

AT 500 HPA A CLOSED HIGH WILL CENTER OVER THE 
CAYMAN ISLES-JAMAICA DURING THE CYCLE...SUPPORTING 
AN EAST-TO-WEST RIDGE ACROSS THE BASIN-CENTRAL 
AMERICA AND SOUTHERN MEXICO. THE RIDGE WILL 
SUPPORT A MID LEVEL CAP INVERSION ACROSS MEXICO-
CENTRAL AMERICA-GREATER ANTILLES-NORTHWEST SOUTH 
AMERICA. OVER COLOMBIA AND VENEZUELA...TO THE 
NORTH OF 05N...THIS WILL INITIALLY FAVOR A 
DECREASE IN CONVECTION. THE GFS RESOLVES A 700 HPA 
INVERTED TROUGH ALONG THE COAST OF COLOMBIA...THAT 
PROGRESSIVELY MOVES ACROSS 82W/83W THROUGH 24 
HRS...87W/88W BY 36 HRS...90W/91W BY 48 HRS... 
93W/94W BY 60 HRS AND WEAKENING BY 72 HRS. IN AN 
UPPER CONVERGENT PATTERN EXPECT MINIMAL RAINFALL 
OVER PANAMA/COSTA RICA IN ASSOCIATION WITH THIS 
TROUGH.

AT 850 HPA...A CLOSED HIGH IS TO MIGRATE FROM THE 
NORTH-CENTRAL GULF OF MEXICO TO THE NORTHWEST 
BAHAMAS BY 48 HRS...WHERE IT REMAINS THROUGH 72 
HRS. AS IT RELOCATES THE ASSOCIATED RIDGE WILL 
BUILD EAST ACROSS THE GREATER ANTILLES...MEANWHILE 
FAVORING A WIND SHIFT ACROSS THE BASIN...WITH LOW 
LEVEL WINDS FROM THE NORTHEAST AT 10-20KT THROUGH 
24 HRS...AND AN EAST-NORTHEAST FLOW TO ESTABLISH 
BY 30-36 HRS. THE FLOW CONVERGES ON THE CARIBBEAN 
PLAINS OF COSTA RICA-SOUTHERN NICARAGUA AND 
WESTERN PANAMA. IN THIS AREA EXPECT RAINFALL 
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM 
TO PEAK BY 36 HRS. THE WEAKENING OF THE NORTHERLY 
TRADES ACROSS CENTRAL AMERICA/EASTERN PACIFIC WILL 
IN-TURN FAVOR THE NORTHWARD MODULATION OF THE 
EASTERN PACIFIC ITCZ...WITH THE CONFLUENT TRADES 
TO ALIGN ALONG 02N BY 42-48 HRS. THIS WILL FAVOR A 
MOIST SURGE ACROSS WESTERN COLOMBIA...AND A RAPID 
INCREASE IN CONVECTION ACROSS THE EJE CAFETERO 
OVER CHOCO AND ANTIOQUIA...WITH RAINFALL 
ACCUMULATION OF 05-15MM/DAY AND MAXIMA OF 35MM. 

A 500 HPA SHORT WAVE TROUGH WILL EXTEND ACROSS THE 
TROPICAL ATLANTIC TO JUST NORTH OF THE GUIANAS 
EARLY THIS CYCLE. AS THE AFOREMENTIONED RIDGE 
EXPANDS ACROSS THE CARIBBEAN BASIN INTO NORTHERN 
SOUTH AMERICA IT WILL DISPLACE THE TROUGH TO ALIGN 
ALONG 45W/50W BY 48 HRS. OVER THIS REGION THE LOW 
LEVEL TRADES WILL RETAIN A NORTHEASTERLY COMPONENT 
THAT IS TO CONVERGE ALONG THE COAST. ALTHOUGH THE 
ONSHORE FLOW PERSISTS...THE DISPLACEMENT OF THE 
MID LEVEL TROUGH WILL LEAD TO A GRADUAL INCREASE 
IN UPPER CONVERGENCE THROUGH 54-60HRS THAT IS TO 
INHIBIT ORGANIZED CONVECTION. MEANWHILE EXPECT 
RAINFALL ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 
15-20MM.  

A 500 HPA POLAR TROUGH OVER THE ATLANTIC ALONG 60W 
TO 30N AT 24 HRS WILL MOVE ACROSS 55W/60W BY 48 
HRS...TO CONTINUE ACROSS 45W/50W BY 72 HRS. THE 
TROUGH SUPPORTS A SURFACE FRONT ACROSS THE 
NORTHWEST BAHAMAS-FLORIDA KEYS...FORECAST TO MOVE 
TO THE CENTRAL BAHAMAS-STRAITS OF FLORIDA BY 24 
HRS. BY 36 HRS IT IS TO CONTINUE ACROSS THE 
CENTRAL/SOUTHERN BAHAMAS-STRAITS OF FLORIDA-INTO 
THE GULF OF MEXICO. A 1029-1031 HPA HIGH OVER THE 
SOUTHEAST USA WILL BUILD A RIDGE BEHIND THIS 
FRONT...DISPLACING THE FRONT ALONG 22N/23N TO THE 
TURKS AND CAICOS-SOUTHEAST BAHAMAS. BY 60 HRS IT 
IS TO ALIGN ALONG THE NORTHERN COAST OF 
HISPANIOLA-CUBA...AND BY 72 HRS THE FRONT WILL 
MOVE TO THE NORTHERN LEEWARD-VIRGIN ISLES-PUERTO 
RICO-HISPANIOLA...WHILE THE TAIL END CURVES AROUND 
THE RIDGE ACROSS CUBA. BY 84 HRS IT WILL MOVE OVER 
GUADELOUPE OVER THE FRENCH ISLES TO JAMAICA. 
ALTHOUGH THE GFS DOES NOT FORECAST SIGNIFICANT 
RAINFALL TO DEVELOP IN ASSOCIATION WITH THIS 
SYSTEM...THE HIGHER RESOLUTION NAM DOES FORECAST 
ORGANIZED CONVECTION TO DEVELOP AS IT ENTERS 
PUERTO RICO-DOMINICAN REPUBLIC...WITH RAINFALL 
ACCUMULATION OF 05-15MM/DAY AND MAXIMA OF 20MM. AT 
72-96 HRS LIGHT TO MODERATE RAINFALL WILL AFFECT 
THE LEEWARD/NORTHERN FRENCH ISLES...WITH 
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM. 

MARTINEZ...SNET (EL SALVADOR)
WILLIAMS...BMS (BARBADOS)
DAVISON...NCEP (HPC)
$$