000 AXNT20 KNHC 221801 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT FRI SEP 22 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... HELENE IS ACCELERATING NORTHEASTWARD AT 18 KT OVER THE OPEN WATERS OF THE CENTRAL NORTH ATLANTIC. IT IS CENTERED NEAR 34.4N 54.2W OR ABOUT 63O MILES EAST-NORTHEAST OF BERMUDA AT 22/1500 UTC. ESTIMATED MINIMUM CENTRAL PRESSURE IS 970 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. THE SATELLITE PRESENTATION OF HELENE HAS DEGRADED SLIGHTLY OVER THE LAST SEVERAL HOURS DUE TO PROBABLY AN INCREASING VERTICAL SHEAR AND DECREASING SSTS. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION COVERS THE AREA FROM 33N-35N BETWEEN 52W-55W. SIMILAR CONVECTION IS ALSO SEEN IN A CURVED BAND NORTH OF THE CENTER AND ALONG 36N55W 38N53W 39N52W. THE CYCLONE SHOULD GRADUALLY WEAKEN AS IT SLOWLY LOSES TROPICAL CHARACTERISTICS DURING THE NEXT COUPLE OF DAYS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 39W S OF 19N WITH A 1010 MB LOW ALONG THE WAVE NEAR 12N MOVING W 15 KT. BROAD MID LEVEL CYCLONIC ROTATION COVERING A LARGE AREA WITH CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION FROM 10N-19N BETWEEN 32W-41W. THIS SYSTEM HAS NOT BECOME ANY BETTER ORGANIZED THIS MORNING...BUT IT STILL HAS SOME POTENTIAL FOR SLOW DEVELOPMENT OVER THE NEXT COUPLE OF DAYS AS IT MOVES TOWARD THE WEST-NORTHWEST OR NORTHWEST AT 10 TO 15 MPH. TROPICAL WAVE IS ALONG 53W S OF 17N WITH A 1012 MB LOW ALONG THE WAVE NEAR 13N MOVING W NEAR 10 KT. SOME CYCLONIC ROTATION IS EVIDENT ON SATELLITE IMAGERY WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 12N-13N BETWEEN 51W-53W. ACCORDING TO THE GFS MODEL...THIS TROPICAL WAVE IS EXPECTED TO ENTER THE EASTERN CARIBBEAN ON SUNDAY. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N14W 10N26W 12N38W 10N45W 12N53W 8N60W. APART FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS FOUND FROM 5N-10N E OF 30W TO JUST INLAND OVER AFRICA. A NEW CLUSTER OF SCATTERED MODERATE/ ISOLATED STRONG CONVECTION IS JUST MOVING OUT OF THE AFRICAN COAST FROM 11N-13N. ...DISCUSSION... GULF OF MEXICO... VERY LARGE UPPER LOW IS MOVING THROUGH THE N/CENTRAL PLAIN STATES WITH AN UPPER TROUGH MOVING ACROSS TEXAS INTO THE NW GULF COAST. THIS CONTINUES TO BRING DRY AIR TO THE TEXAS COAST AND NORTHERN MEXICO. AN UPPER LOW IS OVER THE YUCATAN CHANNEL NEAR 22N85W. UPPER ANTICYCLONE ANCHORED ALONG THE W COAST OF MEXICO NEAR PUERTO VALLARTA EXTENDS A RIDGE ACROSS THE WESTERN GULF ALONG 27N88W...THEN OVER FLORIDA INTO THE W ATLC. MODERATE TO STRONG RETURN SURFACE FLOW IS GENERATING SCATTERED SHOWERS AND TSTMS N OF 28N TO INLAND OVER SE US...PARTICULARLY ACROSS THE FLORIDA PANHANDLE AND SOUTHERN ALABAMA. DOPPLER RADAR IS SHOWING SCATTERED SHOWERS AND ISOLATED TSTMS OVER SOUTH FLORIDA...THE FLORIDA KEYS AND COASTAL WATERS ASSOCIATED WITH A WEAK FRONTAL BOUNDARY LOCATED OVER THIS AREA EXTENDING NORTHWEST INTO THE EASTERN GULF OF MEXICO. THE NEXT COLD FRONT IS FORECAST TO ENTER THE NW GULF WATERS ON SUN. CARIBBEAN SEA... AN UPPER LOW IN OVER THE YUCATAN CHANNEL NEAR 22N85W. THIS LOW IS GENERATING SCATTERED SHOWERS OVER WESTERN CUBA AND THE COASTAL WATERS...INCLUDING THE ISLE OF YOUTH. THIS LOW IS ALSO PRODUCING SCATTERED SHOWERS/THUNDERSTORMS OFF THE COAST OF NICARAGUA/HONDURAS FROM 12N-18N BETWEEN 81W-85W WITH A LINE OF SIMILAR ACTIVITY EXTENDING FROM E PANAMA/COLOMBIA NEAR 8N77W NE TO 12N82W. UPPER HIGH COVERS THE REMAINDER OF THE CARIBBEAN ANCHORED OVER E CUBA NEAR 20N78W. VERY DRY AIR...RESULTING IN MODERATE TO STRONG SUBSIDENCE COVERS THE EAST-CENTRAL CARIBBEAN EAST OF 74W. ELY WINDS GENERALLY ABOUT 15KT DOMINATE THE BASIN. TRADE WINDS SHOULD INCREASE ACROSS THE CARIBBEAN DURING THE UPCOMING WEEKEND AS HIGH PRES BUILDS N OF THE AREA. ATLANTIC OCEAN... THE UPPER RIDGE THAT CROSSES THE GULF ALSO COVERS FLORIDA AND THE W ATLC TO BEYOND 32N70W. THIS IS DRAWING DRY AIR EAST OF THE BAHAMAS AND WEST 64W. A WEAK UPPER TROUGH LIES JUST EAST OF THE RIDGE ALONG 63W. THIS FEATURE IS GENERATING SCATTERED SHOWERS FROM 22N-26N BETWEEN 58W-62W. UPPER HIGH ASSOCIATED WITH HURRICANE HELENE COVERS AN AREA N OF 23N BETWEEN 48W-57W. A BROAD UPPER TROUGH IS OVER THE E-CENTRAL ATLC ALONG 31N38W 24N45W TO A CUT-OFF LOW NEAR 20N48. UPPER HIGH ANCHORED JUST NW OF THE CAPE VERDE ISLANDS NEAR 18N27W COVERS THE REMAINDER OF THE E ATLC. AT THE SURFACE...A COLD FRONT ENTERS THE AREA EAST OF BERMUDA NEAR 32N62W AND CONTINUES MAINLY WEST TO 30N78W. A NARROW BAND OF LOW CLOUDS IS ASSOCIATED WITH THE FRONT SOUTH OF 30N. A 1025 MB HIGH IS LOCATED N OF THE REGION WITH A RIDGE EXTENDING S TO 20N AND EAST OF 50W. PATCHES OF LOW/MID CLOUDS ARE OBSERVED UNDER THE INFLUENCE OF THIS SURFACE RIDGE. $$ GR