[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231753
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT SEP 23 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 REGAINED HURRICANE STRENGTH THIS MORNING. EARLIER
QUIKSCAT PASS INDICATED THAT HELENE CONTAINED A LARGE AREA OF
HURRICANE FORCE WINDS SW OF THE CENTER. A SUBTROPICAL
CLASSIFICATION ALSO SUPPORTED THE HURRICANE FORCE OF 80 KT.
HELENE IS CENTERED NEAR 37.7N 46.4W OR ABOUT 1055 NM WEST OF THE
AZORES AT 23/1500 UTC MOVING EAST-NORTHEAST AT 22 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 970 MB. MAXIMUM SUSTAINED WIND SPEED
IS 80 KT WITH GUSTS TO 100 KT. SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/ WTNT23 KNHC
FOR MORE DETAILS. SATELLITE IMAGERY SHOWED THAT A SMALL AREA OF
DEEP CONVECTION DEVELOPED OVER AND JUST NORTH OF THE CENTER
EARLY THIS MORNING. CURRENTLY THIS AREA OF DEEP CONVECTION IS
MOVING EWD AND AWAY FROM THE LOW LEVEL CENTER. SCATTERED
MODERATE CONVECTION IS FROM 37N-38N BETWEEN 46-48W. DENSE
OVERCAST CLOUDS WITH SHOWERS/ THUNDERSTORMS COVERS A LARGER AREA
FROM 34N-46N BETWEEN 42W-53W. EVEN THOUGH HELENE HAS
STRENGTHENED...IT CONTINUES TO LOSE TROPICAL CHARACTERISTICS AND
IS EXPECTED TO TRANSFORM INTO AN EXTRATROPICAL CYCLONE LATER
TODAY.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 42W/43W S OF 16N. A 1010 MB LOW IS
BEHIND THE WAVE AXIS NEAR 16.5N39.5N. BROAD LOW/MID LEVEL
CYCLONIC ROTATION COVERING A LARGE AREA WITH CLUSTERS OF
SCATTERED MODERATE/STRONG CONVECTION WITHIN 60-80 NM NORTH AND
EAST OF THE LOW LEVEL CENTER. SLOW DEVELOPMENT OF THIS SYSTEM IS
POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES TOWARD THE
NORTHWEST AT ABOUT 10 MPH. MEANWHILE...THE TROPICAL WAVE WILL
CONTINUE TO MOVE WWD AT 10-15 KT.

TROPICAL WAVE IS ALONG 58W S OF 20N MOVING W 10 KT. THE WAVE
SHOWS AN INVERTED-V CLOUD PATTERN ON SATELLITE PICTURES.
SCATTRED SHOWERS AND ISOLATED TSTMS ARE RELATED TO THE WAVE.
PART OF THIS SHOWER ACTIVITY IS ALREADY AFFECTING THE WINDWARD
ISLANDS. THE WAVE WILL ENTER THE EASTERN CARIBBEAN LATE TODAY
AND IS EXPECTED TO MOVE ACROSS THE VIRGIN ISLANDS AND PUERTO
RICO LATE SUNDAY THROUGH MONDAY.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N16W 9N30W 13N40W 10N49W 12N56W.
OUTSIDE FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
6N-11N BETWEEN 14W-20W. SCATTERED MODERATE CONVECTION WITHIN 150
NM EITHER SIDE OF THE ITCZ AXIS BETWEEN 27W-31W.

...DISCUSSION...
GULF OF MEXICO...
AN UPPER LOW CONTINUES TO SPIN IN THE SE GULF NEAR 23N87W.
ABUNDANT UPPER LEVEL MOISTURE IS ON THE EASTERN SIDE OF THE LOW
COVERING THE NW CARIBBEAN...WESTERN CUBA AND MOST OF EASTERN
GULF. THIS LOW IS GENERATING SCATTERED SHOWERS OVER THIS AREA.
AN UPPER ANCHORED OVER NE MEXICO EXTENDS A RIDGE EWD ACROSS THE
WESTERN HALF OF THE GULF...WHERE ABUNDANT DRY UPPER AIR IS
FOUND. VERY DRY AIR ALSO COVERS NORTHERN MEXICO N OF 25N.
ANOTHER UPPER ANTICYCLONE DOMINATES THE STATE OF FLORIDA AND THE
W ATLC. MODERATE TO STRONG RETURN SURFACE FLOW COVERS MUCH OF
THE GULF...AHEAD OF THE NEW COLD FRONT THAT IS EXPECTED TO MOVE
OFF THE TEXAS COAST ON SUNDAY AND EXTEND FROM THE FLORIDA BIG
BEND TO NEAR TAMPICO MEXICO ON MONDAY.

CARIBBEAN SEA...
THE UPPER LOW CENTERED IN THE SE GULF COVERS THE AREA N OF 19N W
OF 82W TO OVER THE YUCATAN PENINSULA/CHANNEL AND W CUBA. THIS
LOW COMBINED WITH THE BROAD UPPER RIDGE OVER THE W ATLC IS
GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
N OF 17N FROM 74W-85W AND GIVING THE REMAINDER OF THE CARIBBEAN
NE UPPER FLOW WITH MOSTLY DRY AIR. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE S OF 10N FROM COLOMBIA TO COSTA RICA.
SCATTERED SHOWERS ARE MOVING OVER THE WINDWARD ISLANDS AHEAD OF
AN APPROACHING TROPICAL WAVE.

ATLANTIC OCEAN...
BROAD UPPER RIDGE COVERS THE W ATLC ANCHORED BY AN UPPER HIGH
OFF THE NE FLORIDA COAST NEAR 28N78W. A WEAK UPPER LOW MOVING SW
IS CENTERED N OF PUERTO RICO NEAR 21N65W AND COULD BRING
ISOLATED TO SCATTERED SHOWERS TO HISPANIOLA AND THE SE BAHAMAS
ON SUNDAY. NARROW UPPER TROUGH EXTENDS FROM AN UPPER LOW N OF
THE REGION NEAR 32N38W SSW INTO THE W TROPICAL ATLC NEAR 16N52W.
BROAD UPPER HIGH ANCHORED NW OF THE CAPE VERDE ISLANDS NEAR
18N26W COVERS THE REMAINDER OF THE E ATLC. AT THE SURFACE...
W ATLC SURFACE RIDGE EXTENDS FROM A 1023 MB HIGH LOCATED N OF
THE REGION ACROSS THE SE U.S AND FAR E GULF OF MEXICO AS WELL AS
THE BAHAMAS AND CENTRAL CUBA.  THIS SYSTEM IS MOVING MAINLY EAST
ALLOWING THE ACTIVE WEATHER THAT IS AFFECTING THE CENTRAL U.S.
TO ALSO MOVE EWD TOWARD THE EAST COAST. THE E ATLC RIDGE COVERS
THE REGION N OF 24N E OF 40W ANCHORED BY A 1022 MB HIGH NEAR
32N32W. THIS FEATURE IS FORECAST TO MOVE SE DURING THE NEXT 24
HOUR.  A BAND OF LOW/MID CLOUDS WITH EMBEDDED SHOWERS ENTERS THE
AREA NEAR 32N44W THEN CONTINUES SW ALONG 27N50W 26N54W. THIS
BAND IS WRAPPING INTO HELENE.

$$
GR





This weather bulletin was brought to you by:
www.nashvilleweather.net