[Tropical] Tropical Weather Discussion

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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







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