000 AXNT20 KNHC 040004 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU SEP 03 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2115 UTC. ...SPECIAL FEATURES... TROPICAL DEPRESSION ERIKA IS CENTERED NEAR 16.7N 65.3W AT 03/2100 UTC OR ABOUT 130 MILES...205 KM...SOUTH-SOUTHEAST OF SAN JUAN PUERTO RICO AND ABOUT 325 MILES...525 KM...EAST-SOUTHEAST OF SANTO DOMINGO IN THE DOMINICAN REPUBLIC MOVING W AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 15N-17N BETWEEN 64W-65W. WIDELY SCATTERED MODERATE CONVECTION IS ALSO E OF THE CENTER FROM 14N-17N BETWEEN 60W-63W. 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 18W S OF 17N MOVING W NEAR 10 KT. A 1009 MB LOW IS ALONG THE WAVE AXIS NEAR 11N18W. SATELLITE IMAGERY AND CIMSS WAVETRAK MODEL GUIDANCE SHOW BROAD CYCLONIC TURNING ALONG THE WAVE AXIS BETWEEN 13W-27W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 14N-16N BETWEEN 18W-21W. SCATTERED SHOWERS COVERS A LARGE AREA FROM 8N-17N BETWEEN 17W-25W. TROPICAL WAVE IS ALONG 32W S OF 20N MOVING W NEAR 10 KT. A 1013 MB LOW IS ALONG THE WAVE AXIS NEAR 14N32W. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY...HOWEVER...VISIBLE SATELLITE IMAGERY INDICATES A DRY SAHARAN AIR LAYER SURROUNDING THE WAVE...THUS INHIBITING ANY SIGNIFICANT DEEP CONVECTION. MOST SCATTERED SHOWERS AND WIDELY SCATTERED MODERATE CONVECTION ARE EMBEDDED WITHIN THE ITCZ FROM 5N-11N BETWEEN 26W-36W. TROPICAL WAVE IS ALONG 49W S OF 17N MOVING W 10 KT. THE WAVE REMAINS LOW-AMPLITUDE AND EMBEDDED WITHIN THE ITCZ AT THE LEADING EDGE OF A MOISTURE MAXIMUM AS INDICATED BY THE TPW IMAGERY. CONVECTION IS LIMITED TO ISOLATED SHOWERS FROM 11N-14N BETWEEN 45W-49W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N14W 11N32W 9N50W 10N61W. ASIDE FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS FROM 7N-9N BETWEEN 24W-26W. ...DISCUSSION... GULF OF MEXICO... AS OF 2100 UTC...A 1011 MB SURFACE LOW IS CENTERED IN THE E GULF NEAR 27N85W. A SURFACE TROUGH EXTENDS NE ACROSS CENTRAL FLORIDA TO 29N80W. ANOTHER SURFACE TROUGH EXTENDS S FROM THE LOW TO THE YUCATAN CHANNEL NEAR 22N86W. WIDELY SCATTERED MODERATE CONVECTION IS OVER THE SE GULF...S FLORIDA...W CUBA...AND THE YUCATAN PENINSULA. ELSEWHERE...ISOLATED MODERATE CONVECTION IS OVER THE SW GULF S OF 23N AND W OF 94W. THE REMAINDER OF THE GULF HAS FAIR SKIES WITH LIGHT WINDS. IN THE UPPER LEVELS...A LARGE UPPER LEVEL TROUGH IS OVER THE GULF WITH AXIS ALONG 89W EXTENDING TO THE YUCATAN PENINSULA. EXPECT...AN UPPER LEVEL LOW TO FORM OVER THE E GULF...AND AN UPPER LEVEL RIDGE TO MOVE OVER THE W GULF...IN 24 HOURS. ALSO EXPECT...CONVECTION TO PERSIST OVER THE SAME AREAS MENTIONED ABOVE FOR THE NEXT 24 HOURS. CARIBBEAN SEA... SEE TROPICAL DEPRESSION ERIKA ABOVE. IN ADDITION...THE CONVECTION ASSOCIATED WITH ERIKA IS SUPPORTED ALOFT BY UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 13N65W. ELSEWHERE... SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS OVER THE SW CARIBBEAN S OF 11N AND W OF 75W. EXPECT...MORE CONVECTION OVER THE LESSER ANTILLES...THE SW CARIBBEAN...AND CENTRAL AMERICA OVER THE NEXT 24 HOURS. THE ATLANTIC OCEAN... A 1010 MB LOW IS CENTERED IN THE W ATLC NEAR 33N76W WITH A SURFACE TROUGH EXTENDING SW TO COCOA BEACH FLORIDA. SCATTERED SHOWERS ARE WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH. ANOTHER SURFACE TROUGH EXTENDS FROM 31N75W TO THE N BAHAMAS AT 25N77W. SCATTERED SHOWERS AND TSTMS ARE FROM 22N-32N BETWEEN 72W-79W. STRONG MIDDLE TO UPPER LEVEL MOIST SLY FLOW ALOFT AND UPPER DIFFLUENCE IS FURTHER ENHANCING THE CONVECTION ACROSS THE W ATLC. TO THE EAST OF THIS ACTIVITY...A BROAD UPPER LEVEL RIDGE COVERS THE REMAINDER OF THE W ATLC ANCHORED NEAR 31N69W. A UPPER LEVEL LOW IS CENTERED NEAR 26N60W. UPPER LEVEL DIFFLUENCE E OF THE UPPER LOW IS GENERATING SCATTERED SHOWERS FROM 24N-29N BETWEEN 50W-56W. THE REMAINDER OF THE CENTRAL AND ERN ATLC IS DOMINATED BY RATHER BENIGN UPPER LEVEL FEATURES AND A BROAD SURFACE RIDGE N OF 22N W OF 70W. THIS SURFACE RIDGE IS ANCHORED BY A 1025 MB HIGH N OF THE REGION CENTERED NEAR 33N42W. $$ FORMOSA