000 AXNT20 KNHC 311745 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN MAY 31 2009 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1615 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 29W S OF 8N MOVING AT ABOUT 15 KT. WHILE WAVE REMAINS EMBEDDED WITHIN THE ITCZ...A SLIGHT CYCLONIC TURNING OF THE LOW LEVEL CLOUDS IS EVIDENT NEAR THE WAVE AXIS AROUND 5N ON VISIBLE SATELLITE IMAGERY. THE WAVE CAN ALSO BE DETECTED FROM THE TOTAL PRECIPITABLE WATER SHOWING A MAXIMUM EAST OF THE WAVE AXIS. THE SYSTEM IS ANALYZED WELL IN ECMWF WITH MAXIMUM AMPLITUDE NEAR 850 MB...WHILE GFS HAS LITTLE SIGNATURE OF THE WAVE. SCATTERED MODERATE CONVECTION IS FROM 2N-6N BETWEEN 27W-32W. A TROPICAL WAVE IS ALONG 58W S OF 14N MOVING W AT 10-15 KT. WAVE EXHIBITS A FAIRLY WELL DEFINED LOW-LEVEL CLOUD SIGNATURE AND COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE EAST OF THE WAVE AXIS AS INDICATED BY THE TOTAL PRECIPITABLE WATER IMAGERY. THE WAVE IS DEPICTED WELL IN THE 700 AND 850 MB WIND FIELDS FROM THE GFS AND ECMWF MODELS. ISOLATED MODERATE CONVECTION IS S OF 8N BETWEEN 55W-59W. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 7N11W 2N35W AND CONTINUES ALONG THE EQUATOR INTO NE BRAZIL NEAR 2N50W. ISOLATED MODERATE CONVECTION IS OCCURRING WITHIN 120 NM OF THE ITCZ AXIS FROM 23W TO THE AFRICAN COAST AND FROM 27W TO 45W. ...DISCUSSION... GULF OF MEXICO... AS OF 1500 UTC...A STATIONARY FRONT EXTENDS FROM THE WESTERN ATLANTIC ACROSS EXTREME SOUTHERN FLORIDA AND INTO THE GULF ALONG 26N81W 24N88W 23N96W. DEEP CONVECTION DIMINISHED ALONG THE FRONT OVERNIGHT...BUT HAS RETURNED WITH SCATTERED MODERATE/ ISOLATED STRONG CONVECTION WITHIN 60 NM OF THE FRONT FROM 83W TO 89W AND IN SOUTHERN FLORIDA ALONG AND SOUTH OF THE FRONT. A SURFACE TROUGH EXTENDS FROM EAST OF THE NE FLORIDA COAST... ACROSS THE NORTHERN PENINSULA OF FLORIDA AND INTO THE NE GULF OF MEXICO ALONG 29N83W 28N87W. NO SIGNIFICANT WEATHER IS OCCURRING IN CONNECTION WITH THIS WEAK FEATURE. ANOTHER SURFACE TROUGH IS LOCATED SOUTH OF THE STATIONARY FRONTAL BOUNDARY IN THE BAY OF CAMPECHE ALONG 22N93W 18N93W AND INTO SOUTHERN MEXICO. THIS FEATURE HAS BEEN MOVING ABOUT 5 KT TOWARD THE WEST OVER THE LAST TWO DAYS AND MAY BE ASSOCIATED WITH AN OTHERWISE UNIDENTIFIED EASTERLY WAVE MOVING ACROSS CENTRAL AMERICA. WHILE NO DEEP CONVECTION IS ASSOCIATED WITH THIS FEATURE AT THIS TIME...A SQUALL LINE MOVED OFF OF THE PACIFIC COAST OF SOUTHERN MEXICO AND INTO THE GULF OF TEHUANTEPEC EARLY THIS MORNING. SURFACE WINDS...AWAY FROM THE AREAS OF DEEP CONVECTION...ARE WEAK THROUGHOUT THE GULF. IN THE UPPER LEVELS...RELATIVELY UNIFORM ZONAL WINDS ARE PRESENT ACROSS THE GULF WITH SOME DIFFLUENT FLOW IN THE SOUTHEASTERN GULF SUPPORTING THE DEEP CONVECTION ALONG THE FRONT. CARIBBEAN SEA... NO SIGNIFICANT SURFACE FEATURES ARE PRESENT TODAY OVER THE CARIBBEAN. INDEED...THE ONLY NOTEWORTHY DEEP CONVECTION CAN BE SEEN IN THE SOUTHWESTERN CARIBBEAN WITH ISOLATED MODERATE CONVECTION SOUTH OF 12N WEST OF 80W. THIS MAY BE IN ASSOCIATION WITH THE EASTWARD EXTENSION OF THE PACIFIC ITCZ ACROSS CENTRAL AMERICA. TOTAL PRECIPITABLE WATER IMAGERY SHOWS THAT A DISTINCT TONGUE OF DRY AIR...POSSIBLY A SAHARAN AIR LAYER...IS PRESENT THROUGHOUT MOST OF THE CARIBBEAN. SURFACE WINDS ACROSS THE CARIBBEAN ARE TYPICALLY 20 KT OR LESS...WITH THE EXCEPTION OF SOME ENHANCED TRADEWINDS OF UP TO 25 KT JUST NORTH OF COLUMBIA AND WESTERN VENEZUELA. IN THE UPPER LEVELS...AN UPPER TROUGH IS INDUCING SUBSIDENCE THROUGHOUT THE REGION. ATLANTIC OCEAN... THE AFOREMENTIONED STATIONARY FRONT ACROSS FLORIDA EXTENDS NORTHEASTWARD INTO THE ATLANTIC ALONG 26N80W 28N77W 31N76W. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS OCCURRING WITHIN THE REGION 24-28N AND 71-80W AHEAD OF THE FRONT. MUCH OF THIS CONVECTIVE ACTIVITY IS IMPACTING THE NORTHERN BAHAMAS AND EXTREME SOUTHERN FLORIDA. A WEAK SURFACE TROUGH ALONG 27N56W TO 20N59W IS ASSOCIATED WITH NO SIGNIFICANT CONVECTION AT THIS TIME. ELSEWHERE...A MODEST 1023 MB SURFACE HIGH AT 29N46W DOMINATES THE TROPICAL AND SUBTROPICAL ATLANTIC. TYPICAL TRADEWINDS OF UP TO 20 KT COVER THE ATLANTIC SOUTH OF THE RIDGE. SUBSTANTIAL AMOUNTS OF DRY AIR ARE OBSERVED FROM THE TOTAL PRECIPITABLE WATER IMAGERY NORTH OF 8N AND EAST OF 60W. IN THE UPPER LEVELS...A STRONG SHORT WAVE IS OBSERVED ALONG THE SE UNITED STATES COAST LINE AND THE DIFFLUENT FLOW AT THE SOUTHERN EXTENT OF THE TROUGH IS ACCENTUATING THE CONVECTION ALONG AND AHEAD OF THE COLD FRONT. A CLOSED UPPER LOW IS OCCURRING NEAR 22N61W AND IS ASSOCIATED WITH A SUBSIDENT ENVIRONMENT. A STRONG SUBTROPICAL JET STREAM SOUTHEAST OF THE UPPER LOW IS ADVECTING SUBSTANTIAL AMOUNTS OF UPPER LEVEL CLOUDINESS AND MOISTURE NORTHEASTWARD FROM THE ORIGINATING CONVECTION OVER SOUTH AMERICA. $$ LANDSEA