000 AXNT20 KNHC 200003 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST MON NOV 19 2012 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF GUINEA-BISSAU AT 12N16W TO 8N21W. THE ITCZ BEGINS AT 8N21W AND CONTINUES ALONG 8N34W 10N47W 7N59W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 5N-9N BETWEEN 20W-34W. ISOLATED MODERATE CONVECTION IS FROM 9N-11N BETWEEN 52W-56W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL RIDGING COVERS THE GULF OF MEXICO PROVIDING MOSTLY NORTHWESTERLY FLOW ALOFT. DRY AIR CONTINUES TO COVER THE MAJORITY OF THE AREA PROVIDING FAIR WEATHER. THE UPPER RIDGE SUPPORTS A SURFACE RIDGE ACROSS THE SE CONUS WHICH EXTENDS ACROSS THE NORTHERN GULF AND INTO THE SW GULF. HOWEVER...AN UPPER LEVEL TROUGH IN THE WEST ATLC SUPPORTS A WEAK COLD FRONT THAT EXTENDS THROUGH THE BAHAMAS TO THE FLORIDA STRAITS INTO THE FAR SE GULF ALONG 23N81W 24N86W. NE WINDS UP TO 20 KT ARE NORTH OF THE FRONT. A SURFACE TROUGH IS ALSO TO THE WEST EXTENDING ACROSS THE YUCATAN PENINSULA ALONG 23N90W TO 18N85W. ISOLATED SHOWERS ARE WITHIN 120 NM OF THE TROUGH AXIS WITH POSSIBLE ISOLATED SHOWERS WITHIN 60 NM SOUTH OF THE FRONT. THE TROUGH IS EXPECTED TO DRIFT WEST WITH POSSIBLE SHOWERS NEAR IT WHILE THE FRONT CONTINUES SOUTH. SURFACE RIDGING WILL REMAIN ACROSS THE NORTHERN GULF. CARIBBEAN SEA... DRY AIR ALOFT COVERS THE NW CARIBBEAN AROUND THE BASE OF AN UPPER LEVEL TROUGH THAT IS ACROSS THE W ATLC. THE DRY AIR IS HELPING PROVIDE FAIR CONDITIONS EXCEPT FOR A FEW ISOLATED SHOWERS NORTH OF HONDURAS NEAR A SURFACE TROUGH THAT EXTENDS FROM THE YUCATAN PENINSULA TO THE NW CARIBBEAN ALONG 23N90W TO 18N85W. MOIST SOUTHWESTERLY FLOW ALOFT COVERS THE CENTRAL CARIBBEAN BETWEEN THE UPPER TROUGH OVER THE FAR NW CARIBBEAN AND AN UPPER LEVEL RIDGE COVERING THE EASTERN CARIBBEAN ALONG 66W. ISOLATED SHOWERS EXTEND FROM COSTA RICA AND PANAMA ALL THE WAY ACROSS HISPANIOLA WITH MORE SCATTERED ACTIVITY WITH ISOLATED THUNDERSTORMS ACROSS THE SW CARIBBEAN FROM 11N-14N BETWEEN 76W-82W. THIS STRONGER ACTIVITY IS ENHANCED BY THE MONSOON TROUGH THAT EXTENDS THROUGH PANAMA TO A SPOT 1008 MB SURFACE LOW NEAR 10N79W. SHOWERS/THUNDERSTORMS ARE ALSO NOTED OVER PUERTO RICO. THE REMAINDER OF THE EASTERN CARIBBEAN IS EXPERIENCING MOSTLY FAIR WEATHER DUE TO THE DRY AIR ALOFT AROUND THE EAST SIDE OF THE UPPER RIDGE. ONLY A FEW WIDELY ISOLATED SHOWERS ARE EMBEDDED WITHIN THE 10-15 KT TRADEWIND FLOW. LITTLE CHANGE IS EXPECTED EXCEPT FOR A WEAK COLD FRONT CURRENTLY THROUGH THE STRAITS OF FLORIDA IS EXPECTED TO DIP SOUTH INTO THE NW CARIBBEAN. POSSIBLE ISOLATED SHOWERS WILL BE ALONG IT. ATLANTIC OCEAN... AN UPPER LEVEL LOW JUST NORTH OF THE DISCUSSION AREA OFF THE SOUTHEAST UNITED STATES COAST SUPPORTS A SERIES OF LOW PRESSURE SYSTEMS AT THE SURFACE. FIRST...A 1012 MB SURFACE LOW IS CENTERED NEAR 30N77W. A WEAK COLD FRONT EXTENDS FROM THE LOW CENTERED SOUTHWARD ACROSS THE BAHAMAS TO THE FLORIDA STRAITS ALONG 26N77W TO 23N81W. NO SHOWERS ACCOMPANY THE FRONT...BUT STRONG NORTHERLY WINDS OF 20-25 KT ARE WEST OF THE LOW CENTER WITH EVEN STRONGER WINDS ALONG THE US COAST NORTH OF THE DISCUSSION AREA. THIS LOW IS EXPECTED TO DISSIPATE AS TWO OTHER LOWS MERGE TO FORM ONE MAIN LOW WHICH WILL CONTINUE TO MOVE THE FRONT SE FOLLOWED BY A SECONDARY FRONT WHICH WILL SWEEP IN BEHIND IT. OF THE OTHER TWO LOWS...ONLY ONE IS IN THE DISCUSSION AREA NEAR 32N68W WITH A SURFACE TROUGH EXTENDING FROM THE CENTER TO NEAR 27N70W. THIS LOW IS EXPECTED TO MOVE NORTH TO MERGE WITH THE THIRD LOW. DIFFLUENCE ALOFT BETWEEN THE UPPER LOW OVER THE WEST ATLC AND AN UPPER LEVEL RIDGE EXTENDING FROM THE EASTERN CARIBBEAN INTO THE CENTRAL ATLC IS SUPPORTING WIDESPREAD SHOWERS/POSSIBLE THUNDERSTORMS FROM 20N-30N BETWEEN 59W-66W...AND FROM 19N-24N BETWEEN 66W-71W NEAR A SURFACE TROUGH ALONG 24N68W TO 18N68W. THE UPPER RIDGE SUPPORTS WEAK SURFACE RIDGING ACROSS THE CENTRAL ATLC. HOWEVER...A BROAD UPPER LEVEL TROUGH OVER THE NORTH CENTRAL ATLC SUPPORTS A COLD FRONT THAT SPREADS FROM THE NE ATLC TO NEAR 32N42W 32N59W WHERE IT CONTINUES TO THE THIRD LOW OVER THE WESTERN ATLC. ISOLATED SHOWERS ARE WITHIN 60 NM OF THE FRONT AXIS. AN UPPER LEVEL LOW IS SOUTH OF THE BROAD UPPER TROUGH NEAR 17N42W SUPPORTING A SURFACE TROUGH ALONG 20N41W TO 11N47W. SCATTERED SHOWERS ARE EAST OF THE AXIS FROM 12N-17N BETWEEN 40W-43W...AND FROM 15N-19N BETWEEN 34W-36W. WEAK SURFACE RIDGING AROUND A 1020 MB HIGH NEAR 30N19W COVERS THE FAR EASTERN TROPICAL ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON