000
AXNT20 KNHC 130501
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EDT SAT MAY 13 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE 
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION 
IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR... 
AND METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0415 UTC.

...TROPICAL WAVES...
TROPICAL WAVE ALONG 37W/38W S OF 9N MOVING W 10 KT IS NOT AS 
WELL DEFINED AS 12 HRS AGO. ISOLATED CONVECTION S OF 4N. 

...ITCZ...
ITCZ AXIS ALONG 6N11W  3N21W  5N38W  4N51W.  CLUSTERS OF 
SCATTERED MODERATE/STRONG CONVECTION WITHIN 180 NM OF AXIS E OF 
19W AND WITHIN 60 NM RADIUS OF 3N24W.  MULTIPLE LAYERS OF CLOUDS 
W OF 41W WITH ISOLATED CONVECTION MAINLY S OF 8N. 

...DISCUSSION...
GULF OF MEXICO...
LARGE DEEP LAYERED CYCLONIC VORTEX OVER GREAT LAKES HAS LONGWAVE 
UPPER LEVEL TROUGH DIG SW ACROSS TEXAS AND CENTRAL MEXICO INTO E 
PAC.  WEAK SURFACE TROUGH REFLECTION CROSSING CENTRAL TEXAS 
LACKS ENOUGH SUPPORT FOR FRONTOGENESIS AT THIS TIME. UPPER WIND 
FLOW BECOMES QUASI-ZONAL OVER GULF OF MEXICO.  THIS SCENARIO 
LIKELY TO CHANGE SOON AS GREAT LAKES VORTEX SINKS SLIGHTLY SE 
BEFORE TURNING NE MON.  WATER VAPOR IMAGES SHOW CONVECTIVE 
DEBRIS FROM LOW PRES CENTER 1006 MB OVER CENTRAL MEXICO AND LOW 
PRES 1007 MB OVER E PAC SUPPLYING HIGH LEVEL MOISTURE OVER WRN 
GULF OF MEXICO.  GFS MAKES THIS MOISTURE AVAILABLE CONGRUENT 
WITH ARRIVAL OF TROUGH IN NW GULF.  EXPECT INCREASE IN CLOUDS
AND PRECIPITATION SUN AS FRONT APPROACHES SE TEXAS COAST.  

HIGH PRES 1015 MB OVER CENTRAL GULF SLIDES NE OF BASIN TONIGHT 
AND INTO ATLC BY SUN FORCED BY INCOMING FRONT.  

CARIBBEAN SEA...
WEAK TRADEWINDS CONTINUE ACROSS ENTIRE BASIN AS ATLC HIGH PRES 
1018 MB RETREATS E FORCED BY SW N ATLC COLD FRONT.  IN THE UPPER 
LEVELS...CARIBBEAN REMAINS UNDER BROAD RIDGE CENTERED JUST OVER 
PANAMA.  SOUTHEASTERN PERIPHERY OF RIDGE HAS PROMPTED SCATTERED 
SHOWERS/ISOLATED TSTMS INLAND AND ALONG IMMEDIATE COAST OF SOUTH 
AMERICA FROM NE VENEZUELA TO COSTA RICA.  UPPER TROUGH IN THE 
CENTRAL ATLC DIPS SW ACROSS TROPICAL ATLC AND EXTREME ERN 
CARIBBEAN INCLUDING THE LESSER ANTILLES.  DRY UPPER AIR AND 
MODERATE/STRONG SUBSIDENCE COVERS AREA E OF 75W SUPPRESSING ANY 
SHOWER ACTIVITY.  SCATTERED CONVECTION OVER YUCATAN 
PENINSULA...GUATEMALA...EL SALVADOR AND HONDURAS AS CONVECTIVE 
DEBRIS FROM E PAC CROSSES INTO CARIBBEAN BASIN.  

ATLANTIC OCEAN...
DEEP LAYERED TROUGH PREVIOUSLY OVER SW N ATLC HAS SHIFTED NE 
PULLING UPPER SUPPORT OF WEAK COLD FRONT PRESENTLY FROM 31N71W 
ACROSS NE BAHAMAS TO WRN CUBA.  CLOUDINESS AND WEAK CONVECTION 
ASSOCIATED MORE TO UPPER LEVEL TROUGH POSITION THAN FRONT AS IT 
RUNS WELL AHEAD OF FRONT N OF 26N FROM 60W TO 66W.  MODERATE AIR 
MASS CONFLUENCE AT UPPER LEVELS PROMPTING STRONG SUBSIDENCE 
BEHIND FRONTAL BOUNDARY RESULTING IN VERY DRY AIR MASS.  

BROAD DEEP LAYERED TROUGH OVER CENTRAL/EAST ATLC N OF 18N FROM 
44-60W.  ASSOCIATED COLD FRONT APPROACHING AREA ALONG 32N FROM 
35W-45W.  SURFACE HIGH PRES 1018 MB CENTERED AT 25N48W BEING 
FORCED E BY INCOMING COLD FRONT OVER SW N ATLC.  SHOWERS/ 
ISOLATED TSTMS ALONG SURFACE TROUGH FROM 31N33W TO 23N43W.  
BROAD UPPER LEVEL RIDGE AT 12N33W MAINTAINS ANTICYCLONIC FLOW 
ACROSS ENTIRE EAST ATLC WITH FAIRLY ZONAL FLOW E OF 40W. 

$$
WALLY BARNES