000 AXNT20 KNHC 021758 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED SEP 02 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 1715 UTC. ...SPECIAL FEATURES... TROPICAL STORM ERIKA IS CENTERED NEAR 16.2N 61.1W AT 02/1800 UTC OR VERY NEAR GUADELOUPE IN THE LEEWARD ISLANDS MOVING W AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. NUMEROUS MODERATE/ SCATTERED STRONG CONVECTION IS FROM 13N-18N BETWEEN 56W-61W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 27W S OF 20N MOVING W NEAR 18 KT. WAVE IS EMBEDDED WITHIN A MAXIMUM OF DEEP LAYER MOISTURE AS INDICATED BY THE TOTAL PRECIPITABLE WATER IMAGERY. CIMSS WAVETRAK MODEL GUIDANCE ALSO INDICATES A BROAD AREA OF LOW-LEVEL VORTICITY IN THE VICINITY OF THE WAVE AXIS. SCATTERED MODERATE CONVECTION IS CONFINED TO THE NRN EXTENT OF THE AXIS FROM 17N-21N BETWEEN 22W-28W. ELSEWHERE...SCATTERED SHOWERS ARE FROM 12N-17N BETWEEN 24W-30W. TROPICAL WAVE EXTENDS FROM 8N39W TO 14N42W MOVING W NEAR 18 KT. THIS WAVE REMAINS EMBEDDED WITHIN THE ITCZ AND MAINTAINS A LOW-AMPLITUDE INVERTED-V SATELLITE PRESENTATION. A LARGE AREA OF SAHARAN DUST IS TO THE N OF THE WAVE ACROSS THE CENTRAL ATLC. SCATTERED MODERATE CONVECTION IS FROM 8N-12N BETWEEN 39W-46W. HOWEVER MOST OF THIS PRECIPITATION IS MORE LIKELY ASSOCIATED WITH THE ITCZ. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 15N17W 14N24W 10N27W 10N39W 9N41W 9N53W. A LARGE CLUSTER OF NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS ACROSS W AFRICA FROM 7N-15N BETWEEN 8W-16W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE AXIS BETWEEN 27W-32W. SIMILAR CONVECTION IS FROM 8N-12N BETWEEN 42W-47W. ...DISCUSSION... GULF OF MEXICO... AS OF 1500 UTC...A STATIONARY FRONT IS ANALYZED ACROSS THE NRN FLORIDA PENINSULA FROM ST. AUGUSTINE TO CEDAR KEY FLORIDA AND INTO A 1015 MB LOW CENTERED NEAR 29N84W. THE STATIONARY FRONT CONTINUES WSW ALONG 26N89W TO 26N94W. A SURFACE TROUGH ALSO EXTENDS ACROSS THE FLORIDA PENINSULA FROM DAYTONA BEACH TO NAPLES AND INTO THE SE GULF NEAR 24N83W. THIS FRONT IS SUPPORTED ALOFT BY AN UPPER LEVEL TROUGH ACROSS THE SE CONUS WHICH DIPS INTO THE NRN GULF REMAINING N OF 26N. MOIST W TO SWLY UPPER LEVEL FLOW COUPLED WITH THE MEANDERING SURFACE STATIONARY BOUNDARY ARE GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 120 NM S OF THE FRONT AS WELL AS E OF THE SURFACE LOW N OF 27N ACROSS THE NE GULF AND NRN PORTIONS OF FLORIDA. THE COASTAL DOPPLER RADAR MOSAIC INDICATES MORE WIDESPREAD SCATTERED SHOWERS AND TSTMS ACROSS THE FLORIDA PENINSULA AND NEARBY COASTAL WATERS S OF 27N. ACROSS THE WRN GULF...AN UPPER LEVEL RIDGE REMAINS ANCHORED ACROSS W/CENTRAL MEXICO AND EXTENDS INTO THE WRN GULF ALONG 22N TO 87W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE UPPER LEVEL RIDGE IS GENERATING SCATTERED SHOWERS AND TSTMS ACROSS THE WRN BAY OF CAMPECHE S OF 22N W OF 93W. CARIBBEAN SEA... AN UPPER LEVEL RIDGE EXTENDS FROM W/CENTRAL MEXICO NEAR 21N105W TO NRN NICARAGUA NEAR 13N84W PROVIDING THE NW CARIBBEAN WITH GENERALLY NLY UPPER LEVEL FLOW AND A MODERATELY STABLE ATMOSPHERE. VERY LITTLE IN THE WAY OF DEEP CONVECTION IS OBSERVED ON SATELLITE IMAGERY WITH ONLY POSSIBLE ISOLATED SHOWERS MOVING ACROSS THE WRN CARIBBEAN ON ENE TRADE WIND SURFACE FLOW. AN UPPER LOW IS CENTERED OVER WRN HISPANIOLA NEAR 18N74W AND THE ASSOCIATED TROUGHING DIPS S TO ERN PANAMA. DRY AND STABLE AIR ALOFT IS NOTED ON WATER VAPOR IMAGERY AND ALONG WITH A LOW-LEVEL SAHARAN AIR LAYER ACROSS MUCH OF THE CENTRAL CARIBBEAN IS INHIBITING ANY DEEP CONVECTION W OF 65W. AS TROPICAL STORM ERIKA TRACKS WWD OVER THE LEEWARD ISLANDS... SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING ACROSS THE FAR ERN CARIBBEAN AND LESSER ANTILLES E OF 63W AS OBSERVED ON THE GUADELOUPE RADAR MOSAIC...WITH MORE INTENSE CONVECTION LOCATED E OF 61W IN THE NEARBY TROPICAL NORTH ATLC WATERS. ATLANTIC OCEAN... THE MAIN FOCUS IS TROPICAL STORM ERIKA LOCATED E OF THE LEEWARD ISLANDS. SEE SPECIAL FEATURES ABOVE. IN THE W ATLC...A STATIONARY FRONT ENTERS THE REGION NEAR 32N77W AND EXTENDS SW TO ST. AUGUSTINE FLORIDA AND INTO THE NE GULF OF MEXICO. A SURFACE TROUGH IS ALSO ANALYZED FROM THE STATIONARY FRONT NEAR 30N80W TO NAPLES FLORIDA WITH SCATTERED SHOWERS AND TSTMS COVERING AN AREA FROM 23N TO BEYOND 32N W OF 76W. A SECOND SURFACE TROUGH EXTENDS FROM THE CENTRAL BAHAMAS NEAR 22N75W TO 30N75W. THIS SURFACE TROUGH ALONG WITH AN UPPER LEVEL UPPER LEVEL DIFFLUENCE ASSOCIATED WITH AN ANTICYCLONIC CIRCULATION CENTERED NEAR 28N72W IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 180 NM EITHER SIDE OF THE SURFACE TROUGH. AN UPPER TROUGH IS OVER THE W/CENTRAL ATLC EXTENDING OVER THE REMAINDER OF THE W ATLC NEAR 32N60W TO AN UPPER LOW OVER WRN HISPANIOLA. POSSIBLE ISOLATED SHOWERS GENERATED BY UPPER LEVEL DIFFLUENCE E OF THE TROUGH AXIS ARE FROM 25N-30N BETWEEN 56W-62W. OTHERWISE...THE REMAINDER OF THE CENTRAL AND ERN ATLC BASIN REMAINS UNDER THE INFLUENCE OF A SURFACE RIDGE THAT IS ANCHORED BY A 1030 MB HIGH CENTERED SW OF THE AZORES NEAR 36N34W. $$ HUFFMAN