000 AXNT20 KNHC 192359 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE SEP 19 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE 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 2315 UTC. ...SPECIAL FEATURES... AT 20/000O UTC GORDON IS NEARING THE CENTRAL AZORES. IT IS CENTERED NEAR 37.8N 30.0W OR ABOUT 170 MILES WEST-SOUTHWEST OF THE ISLAND OF TERCEIRA IN THE AZORES RACING EASTWARD AT 29 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 979 MB. MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH GUSTS TO 90 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC OR THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. GORDON WILL MOVE NEAR OR OVER THE CENTRAL AND EASTERN ISLANDS OF THE AZORES TONIGHT AND EARLY WEDNESDAY AND WILL BE NEARING PORTUGAL AND NORTHWEST SPAIN LATE WEDNESDAY AS A STRONG EXTRATROPICAL CYCLONE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS MAINLY NORTH OF THE CENTER FROM 37N-39N BETWEEN 30W-32W. HURRICANE HELENE IS CENTERED NEAR 24.6N 54.1W OR ABOUT 840 MILES SOUTHEAST OF BERMUDA AT 19/2100 UTC MOVING WEST-NORTHWEST AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 956 MB. MAXIMUM SUSTAINED WIND SPEED IS 95 KT WITH GUSTS TO 115 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/ WTNT23 KNHC FOR MORE DETAILS. HELENE SHOWS TRUE SYMMETRY...A DEEP CENTRAL DENSE OVERCAST AND A WELL-DEFINED EYE FEATURE ALL INDICATIVE OF A MATURE HURRICANE UNDERGOING FLUCTUATIONS IN INTENSITY. GORDON IN CURRENTLY A CATEGORY TWO HURRICANE ON THE SAFFIR SIMPSON HURRICANE SCALE...BUT HAS THE POTENTIAL TO REGAIN A CATEGORY THREE WITH MAXIMUM SUSTAINED WINDS OF 100 KT DURING THE NEXT 24 HOURS. IT IS NOT EXPECTED TO IMPACT ANY LAND MASS ON ITS CURRENT FORECASTED TRACK. A BAND OF MODERATE TO STRONG CONVECTION IS WRAPPING AROUND THE CENTER. THE COLDEST CLOUD TOPS ARE ON THE WEST SIDE. ...TROPICAL WAVES... A TROPICAL WAVE IS APPROACHING THE CAPE VERDE ISLANDS. IT AXIS IS ALONG 21/22W SOUTH OF 21N MOVING WEST AT 10-15 KT. SATELLITE IMAGERY SHOWS SOME TURNING IN THE CLOUD PATTERN NEAR 13N. SCATTERED MODERATE/ISOLATED STRONG CONVECTION BETWEEN THE WAVE AXIS AND THE WEST AFRICAN COAST. TROPICAL WAVE IS ALONG 40W SOUTH OF 20N MOVING WEST AT 10-15 KT. WELL-DEFINED INVERTED-V SIGNATURE WITH ASSOCIATED SCATTERED MODERATE/ISOLATED STRONG CONVECTION E OF THE WAVE AXIS FROM 10N-14N BETWEEN 35W-40W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N15W 9N26W 10N38W 8N42W 6N56W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120-150 NM SOUTH OF THE AXIS E OF 31W TO THE COAST OF AFRICA. A CLUSTER OF SIMILAR CONVECTION IS WITHIN 200 NM NORTH OF AXIS BETWEEN 49W-52W. ...DISCUSSION... GULF OF MEXICO... A DEEP LAYER TROUGH IS MOVING ACROSS THE EASTERN US AND THE NORTH-CENTRAL GULF WATERS. THE ASSOCIATED FRONTAL SYSTEM EXTENDS FROM A 1008 MB SURFACE LOW PRES OVER THE CAROLINAS SOUTH- WESTWARD INTO THE GULF NEAR 30N87W...THEN CONTINUES TO ANOTHER WEAK SURFACE LOW PRES LOCATED NEAR 26N95W. A PRE-FRONTAL TROUGH LIES ALONG 31N82W 28N87W. DOPPLER RADAR DEPICTS A SQUALL LINE MOVING ACROSS NORTHERN FLORIDA AND SCATTERED TO NUMEROUS SHOWERS AND TSTMS OVER CENTRAL AND SOUTH FLORIDA. THE FRONTAL BOUNDARY WILL EXTEND FROM NORTH-CENTRAL FLORIDA TO NE MEXICO WEDNESDAY MORNING AND IS EXPECTED TO CROSS SOUTH FLORIDA DURING THE AFTERNOON. CONTINENTAL DRY AIR IS ENTERING THE NW PORTION OF THE GULF...JUST BEHIND THE FRONT. AN UPPER HIGH IS OVER THE BAY OF CAMPECHE WITH THE UPPER RIDGE EXTENDING NE AHEAD OF THE UPPER TROUGH. THIS RIDGE COVERS A GOOD PORTION OF THE GULF AND THE STATE OF FLORIDA. EAST OF THE RIDGE...A BROAD UPPER TROUGH REMAINS IN THE W ATLC. DIFFLUENCE ALOFT IS ENHANCING THE SHOWER/TSTM ACTIVITY OVER FLORIDA AND THE ADJACENT COASTAL WATERS. THE CARIBBEAN SEA... THE UPPER TROUGH IN THE W ATLC EXTENDS ACROSS THE BAHAMAS AND CUBA INTO THE NW CARIBBEAN WITH AN UPPER LOW OVER CENTRAL CUBA. THE UPPER HIGH THAT IS LOCATED OVER THE BAY OF CAMPECHE ALSO COVERS SOUTH MEXICO AND CENTRAL AMERICA. A MUCH LARGER UPPER HIGH REMAINS IN THE E CARIBBEAN AND IS ANCHORED NOW JUST S OF PUERTO RICO EXTENDING A RIDGE WSW TO 13N80W. THIS FEATURE IS ADVECTING TROPICAL MOISTURE OVER THE SW CARIBBEAN AND GENERATING CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION JUST NORTH OF COLOMBIA AND NEAR LAKE MARACAIBO IN VENEZUELA. SIMILAR CONVECTION IS SEEN OVER CENTRAL AMERICA DUE TO THE CLOSE PROXIMITY OF THE ITCZ AND A DIFLUENT PATTERN ALOFT. THE EASTERN CARIBBEAN REMAINS RATHER DRY...WITH THE TYPICAL AFTERNOON CONVECTION OVER PUERTO RICO AND HISPANIOLA THANKS TO THE LOCAL EFFECTS. THE INVERTED TROUGH MENTIONED DURING THE PREVIOUS DAYS HAS MOVE TO THE SW CORNER OF THE AREA AND IS APPROACHING THE COAST OF NICARAGUA. TRADE WINDS OF 10-15 KT DOMINATE THE ENTIRE BASIN. THE ATLANTIC OCEAN... BROAD UPPER TROUGH EXTENDS FROM AN UPPER LOW N OF THE REGION ACROSS THE BAHAMAS AND CUBA. A SURFACE TROUGH RUNS FROM 31N68W TO 22N77W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN AROUND 80 NM EAST OF THE TROUGH. BROAD UPPER HIGH ANCHORED IN THE E CARIBBEAN EXTENDS A RIDGE NE TO 23N58W JUST W OF HURRICANE HELENE. THIS SYSTEM IS GIVING THE E CARIBBEAN AND THE W TROPICAL ATLC VERY DRY AIR. THE UPPER RIDGE ASSOCIATED WITH HURRICANE HELENE IS ELONGATED N/S. WV IMAGERY SHOWS AN UPPER LOW OVER THE E ATLC NEAR 23N36W. THIS LOW IS GENERATING ISOLATED SHOWERS NORTH OF THE AREA. REMAINDER OF THE E ATLC IS DOMINATED BY AN UPPER HIGH ANCHORED OFF THE COAST OF AFRICA NEAR 17N20W. ACCORDING TO THE 19/2100 SAHARAN AIR LAYER FROM CIMSS...SOME AFRICAN DUST IS STILL AFFECTING THE EASTERN CARIBBEAN...PARTICULARLY THE LESSER ANTILLES. $$ GR