000 AXNT20 KNHC 201757 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN MAY 20 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... TROPICAL STORM ALBERTO IS CENTERED NEAR 31.3N 79.9W AT 20/1800 UTC OR ABOUT 95 NM S OF CHARLESTON SOUTH CAROLINA AND ABOUT 85 NM SE OF SAVANNAH GEORGIA MOVING WSW OR 245 DEGREES AT 5 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. ALBERTO HAS WEAKENED A LITTLE. THE DEEPEST CONVECTION ASSOCIATED WITH THIS TROPICAL CYCLONE HAS DIMINISHED DURING THE MORNING HOURS. DOPPLER RADAR SHOWS BANDS OF SHOWERS WITH EMBEDDED TSTMS MOVING MAINLY ALONG THE GEORGIA COAST AND AWAY FROM THE CENTER. THE OFFICIAL FORECAST KEEPS ALBERTO AT LOW-END TROPICAL-STORM STRENGTH THROUGH WEDNESDAY WITH WEAKENING AND DISSIPATION OCCURRING ON THURSDAY. AN AIR FORCE HURRICANE HUNTER AIRCRAFT IS CURRENTLY APPROACHING ALBERTO TO PROVIDE A BETTER ESTIMATE OF ITS INTENSITY. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 11N32W TO 5N34W MOVING W AT 10-15 KT. WAVE REMAINS EMBEDDED WITHIN AN AREA OF DEEP LAYERED MOISTURE AS DEPICTED ON THE MIMIC-TOTAL PRECIPITABLE WATER ANIMATION. IMAGERY. HOWEVER...THE WAVE IS VOID OF DEEP CONVECTION. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH ENTERS THE E TROPICAL ATLC THROUGH GUINEA AND EXTENDS TO 04N20W WHERE THE ITCZ AXIS CONTINUES ALONG 3N24W TO 6N32W THEN RESTARTS W OF THE TROPICAL WAVE NEAR 5N34W CONTINUING ALONG 2N40W TO INLAND OVER SOUTH AMERICA NEAR 0N51W. MODERATE TO ISOLATED STRONG CONVECTION IS NOTED FROM 2N TO 7N BETWEEN 10W AND 16W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE EXTENDS ALONG THE COAST OF MEXICO AND TEXAS AND DOMINATES THE WESTERN HALF OF THE GULF WHILE AN UPPER LEVEL TROUGH IS NOTED OVER THE EASTERN HALF OF THE GULF AND THE STATE OF FLORIDA. MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY AIR MASS IS SEEN ON WATER VAPOR IMAGERY ACROSS MOST OF THE AREA. AT THE SURFACE...HIGH PRES FROM THE EASTERN UNITED STATES EXTENDS A RIDGE SW INTO THE GULF REGION PRODUCING MAINLY GENTLE TO MODERATE BREEZE. A SURFACE TROUGH REMAINS OVER THE SE GULF AND THE YUCATAN PENINSULA...ALONG THE COAST OF QUINTANA ROO EXTENDING FROM 24N86W TO THE GULF OF HONDURAS AT 16N88W. A WEAK 1009 MB LOW PRES IS ALONG THE TROUGH AXIS NEAR 20N. THIS POSITION IS JUST SOUTH OF COZUMEL THAT HAS BEEN REPORTING HEAVY RAIN AT TIMES. THE TROUGH WILL REMAIN NEARLY STATIONARY THEN WILL BEGIN TO DRIFT NE BEYOND 24 HOURS. CARIBBEAN SEA... AN UPPER ANTICYCLONIC CIRCULATION SITUATED OVER NORTHERN CENTRAL AMERICA EXTENDS A RIDGE ACROSS THE ENTIRE BASIN WITH THE RIDGE AXIS STRETCHING FROM CENTRAL AMERICA THROUGH JAMAICA AND HISPANIOLA INTO THE ATLC OCEAN. UPPER DIFFLUENCE ASSOCIATED WITH THIS FEATURE IS HELPING TO INDUCE SCATTERED MODERATE TO ISOLATED CONVECTION OVER THE WESTERN CARIBBEAN AND CUBA...AS WELL AS OVER THE SW CARIBBEAN WHERE SCATTERED SHOWERS AND TSTMS ARE NOTED... PARTICULARLY S OF 13N BETWEEN 75W AND 80W. AS PREVIOUSLY MENTIONED...A SURFACE TROUGH IS ALONG THE COAST QUINTANA ROO MEXICO AND THE GULF OF HONDURAS. SCATTEROMETER AND SURFACE DATA SHOWED PRETTY WELL THE WIND SHIFT RELATED TO THIS TROUGH. THE PRES GRADIENT BETWEEN ATLC HIGH LOCATED N OF AREA AND THIS PERSISTENT BROAD TROUGHING OVER THE WESTERN CARIBBEAN WILL MAINTAIN MODERATE TO FRESH TRADES ACROSS THE REMAINDER OF THE BASIN DURING THE NEXT SEVERAL DAYS. ATLANTIC OCEAN... ATTENTION REMAINS FOCUSED ON ALBERTO...AN OUT-OF-SEASON TROPICAL CYCLONE. ALBERTO IS THE EARLIEST FORMING TROPICAL STORM IN THE ATLANTIC BASIN SINCE ANA IN 2003. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. AN UPPER LEVEL TROUGH IS OVER FLORIDA AND THE FAR WESTERN ATLC SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 31N75W THROUGH THE NW BAHAMAS INTO SOUTH FLORIDA AND THE KEYS. DOPPLER RADAR SHOWS SCATTERED SHOWERS AND ISOLATED TSTMS NEAR THE TAIL END OF THE TROUGH ACROSS SOUTH FLORIDA AND THE STRAITS OF FLORIDA. A SECOND SURFACE TROUGH EXTENDS FROM 28N72W ACROSS THE SE BAHAMA ISLANDS TO NEAR 21N74W. MOST OF THE ASSOCIATED SHOWER AND TSTM ACTIVITY IS E OF THE TROUGH AXIS...AND UNDER THE INFLUENCE OF AN UPPER LEVEL RIDGE. THE TROUGH SE OF ALBERTO WILL SLOWLY MOVE E THROUGH TUE NIGHT WHILE THE SECOND ONE WILL REMAIN NEAR 71W/72W THROUGH WED. AN UPPER LEVEL LOW IS CENTER NEAR 23N55W WITH A TROUGH EXTENDING SW TO NEAR TRINIDAD AND TOBAGO IN THE WINDWARD ISLANDS. THE LOW IS GENERATING SOME SHOWER ACTIVITY. E OF THIS TROUGH...THERE IS AN UPPER LEVEL HIGH ANCHORED JUST W OF THE CAPE VERDE ISLANDS. AT THE SURFACE...A 1034 MB HIGH PRESSURE CENTERED NEAR 35N37W DOMINATES MOST OF THE EAST AND CENTRAL ATLC. FRESH TRADE WINDS CAN BE FOUND ON THE SOUTHERN PERIPHERY OF THIS HIGH. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GR