000 AXNT20 KNHC 240459 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SUN SEP 24 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0315 UTC. ...SPECIAL FEATURES... HURRICANE HELENE IS CENTERED NEAR 39.1N 41.7W OR ABOUT 691 NM WEST OF THE AZORES AT 24/0300 UTC MOVING EAST-NORTHEAST AT 20 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 973 MB. MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH GUSTS TO 90 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/ WTNT23 KNHC FOR MORE DETAILS. HELENE RETAINS TROPICAL CHARACTERISTICS BUT IS IS EXPECTED TO BECOME EXTRATROPICAL OVER THE NEXT 12 TO 24 HOURS. SCATTERED MODERATE CONVECTION IS WITHIN 250 NM OF THE CENTER IN THE NW QUADRANT. DENSE OVERCAST CLOUDS WITH SHOWERS/THUNDERSTORMS IS FROM 37N-45N BETWEEN 37W-47W. ...TROPICAL WAVES... A 1009 MB LOW IS CENTERED NEAR 19N41W MOVING N 10 KT. LOW WAS PREVIOUSLY ASSOCIATED WITH THE WAVE THAT HAS MOVED FURTHER W AND APPEARS TO BE MOVING N IN RESPONSE TO AN UPPER RIDGE. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION COVER THE AREA FROM 18N-23N BETWEEN 36W-44W. TROPICAL WAVE IS ALONG 44W/45W S OF 19N MOVING W 10 KT. THIS WAVE HAS WEAKENED CONSIDERABLY SINCE THE ASSOCIATED LOW BROKE AWAY ON SAT AFTERNOON. WAVE IS EMBEDDED WITHIN DRY AIR AND HAS NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE IS OVER THE LESSER ANTILLES ALONG 61W/62W S OF 20N MOVING W 10-15 KT. BROAD INVERTED-V SIGNATURE CURVATURE ASSOCIATED WITH THIS WAVE. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 12N-18N BETWEEN 57W-63W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N15W 7N29W 13N38W BECOMING DISTORTED BY THE TROPICAL LOW/WAVE THEN ALONG 10N49W 13N60W 9N62W ACROSS N PORTION OF SOUTH AMERICA AND PANAMA INTO THE E PACIFIC REGION NEAR 9N80W. APART FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL LOW/WAVE...SCATTERED STRONG CONVECTION IS WITHIN 150 NM N OF THE ITCZ AXIS FROM 21W-24W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 250 NM S OF THE ITCZ AXIS FROM 19W-27W WITH CLUSTERS OF SIMILAR CONVECTION FROM 11N-17N BETWEEN 37W-43W. ...DISCUSSION... GULF OF MEXICO... BROAD UPPER TROUGH EXTENDS FROM AN UPPER LOW OVER THE GREAT LAKES INTO TEXAS MOVING INTO THE MISSISSIPPI VALLEY WITH THE ASSOCIATED STRONG COLD FRONT STILL INLAND OVER THE TEXAS COAST. A SQUALL LINE IS ALONG THE TEXAS COAST FROM PORT ARTHUR TO JUST S OF GALVESTON AND WILL BE ENTERING THE NW GULF SHORTLY. AN UPPER HIGH IS CENTERED OVER NE MEXICO NEAR 23N99W WITH A BROAD RIDGE COVERING THE W GULF W OF 90W. ANOTHER UPPER HIGH IS ANCHORED IN THE W ATLC EXTENDING A RIDGE OVER THE E GULF E OF 85W. THE UPPER LOW IS SQUEEZED BETWEEN THESE RIDGES AND CENTERED IN THE SE GULF N OF THE YUCATAN PENINSULA NEAR 23N88W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 24N FROM 83W-87W. MODERATE/STRONG RETURN SURFACE FLOW REMAINS OVER MUCH OF THE GULF. CARIBBEAN SEA... THE UPPER LOW CENTERED IN THE SE GULF COVERS A SMALL PORTION OF NW CARIBBEAN N OF 19N W OF 85W WITH SCATTERED SHOWERS N OF 19N W OF 83W. BROAD UPPER RIDGE OVER THE W ATLC IS GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS N OF 17N FROM 71W-83W AND GIVING THE REMAINDER OF THE CARIBBEAN NE UPPER FLOW WITH MOSTLY DRY AIR. OTHER THAN THE SHOWER ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE OVER THE LESSER ANTILLES THE REMAINDER OF THE CARIBBEAN REMAINS CLEAR TONIGHT. ATLANTIC OCEAN... BROAD UPPER RIDGE COVERS THE W ATLC ANCHORED BY AN UPPER HIGH NEAR 29N74W AND COVERS THE AREA W OF 62W AND GIVING THE CARIBBEAN NE UPPER FLOW. WEAK UPPER TROUGH EXTENDS FROM 25N45W SW TO JUST E OF THE LEEWARD ISLANDS NEAR 18N59W AND IS ENHANCING THE SHOWER ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE OVER THE LESSER ANTILLES. A DEEP LAYERED TROUGH IS PUSHING SE OVER THE CANARY ISLANDS WITH THE ASSOCIATED STATIONARY FRONT N OF THE REGION. BROAD UPPER HIGH ANCHORED NW OF THE CAPE VERDE ISLANDS NEAR 18N27W COVERS THE REMAINDER OF THE E ATLC. AT THE SURFACE...A SURFACE TROUGH IS IN THE CENTRAL ATLC FROM BEYOND 32N41W SW TO 25N58W IN THE WAKE OF HURRICANE HELENE SPLITTING THE SUBTROPICAL RIDGE THAT DOMINATES THE MUCH OF THE ATLC. W ATLC SURFACE RIDGE EXTENDS FROM A 1023 MB HIGH WELL N OF THE REGION THROUGH 32N68W ACROSS TO OVER FLORIDA NEAR 28N84W. THE E ATLC RIDGE COVERS THE REGION N OF 18N FROM 20W-37W ANCHORED BY A 1020 MB HIGH NEAR 32N30W. $$ WALLACE