[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 130011
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON SEP 12 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND 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 FEATURE...

TROPICAL STORM OPHELIA CENTERED NEAR 31.9N 77.6W...OR 160 MILES
ESE OF CHARLESTON SOUTH CAROLINA AND 220 MILES SSW OF CAPE
HATTERAS NORTH CAROLINA...AT 13/0000 UTC MOVING NW 3 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED
WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND THE PUBLIC ADVISORY UNDER HEADERS MIATCPAT1/WTNT31 KNHC FOR
MORE DETAILS.   THE CYCLONE HAS HAD TROUBLE DEVELOPING DEEP
CONVECTION DUE TO IT BEING SITUATED OVER COOL WATERS LESS THAN
80F AS A RESULT OF ITS OWN UPWELLING.  HOWEVER... DROPSONDES
FROM NOAA PLANES ARE SHOWING THAT THE SSTS ARE A LITTLE WARMER
IN THE PATH OF THE CYCLONE WHICH IS NOW SLOWLY MOVING.
CONVECTION IS ALSO DEEPER THAN EARLIER BUT STILL WEAKER THAN
AVERAGE FOR A TROPICAL CYCLONE.  BANDS ARE TRYING TO ORGANIZE IN
A LARGER EYE-LIKE FEATURE ABOUT 45-60 NM FROM THE CENTER WITH
WIDELY SCATTERED WEAK TO MODERATE CONVECTION WITHIN 150 NM OF
THE CENTER.  A FEW RAINBANDS ARE AFFECTING THE COAST FROM CAPE
LOOKOUT TO NEAR CHARLESTON.

...TROPICAL WAVES...

CENTRAL ATLC WAVE ADDED ALONG 32W/33W S OF 15N MOVING W 10 KT.
IT IS A RATHER LOW-LATITUDE WAVE WITH NO REAL SIGNAL IN THE
DAKAR TIMESECTION.  THE WAVE PROBABLY LEFT THE COAST OF AFRICA
ON THE 9TH AND HAS BEEN MOVING RATHER SLOWLY WESTWARD ACCORDING
TO LONG-TERM SATELLITE LOOPS. THE GFS/ECMWF ALSO ANALYZED A WAVE
IN THAT LOCATION WITH THE TYPICAL MOISTURE INCREASE AND WIND
PROFILE OF A TROPICAL WAVE.  WIDELY SCATTERED MODERATE
CONVECTION FROM 11N-14N BETWEEN 32W-35W.

W-CENTRAL ATLC WAVE TILTED ALONG 8N47W 15N45W 22N41W MOVING W
10-15 KT. THE WAVE IS WELL-DEFINED BASED ON LOW/MID CLOUD
TURNING IN SATELLITE IMAGERY.  IN FACT IT LOOKS LIKE THE WAVE
JUST PASSED BUOY 41041 WITH NE WINDS SHIFTING TO ESE WITHIN THE
PAST 3 HOURS.  CONVECTION IS LIMITED TO NEAR THE ITCZ AND MOSTLY
BEHIND THE WAVE DUE TO DRY AIR FROM AFRICA.  ISOLATED WEAK/
MODERATE CONVECTION FROM 9N-13N BETWEEN 38W-45W.

CENTRAL CARIBBEAN WAVE ALONG 75W S OF 24N MOVING W 15-20 KT. THE
WAVE IS MOVING IN TANDEM WITH AN INVERTED UPPER LEVEL TROUGH AND
THE TWO ARE HARD TO SEPARATE.  ISOLATED MODERATE CONVECTION FROM
14N-18N BETWEEN 72W-78W.

TROPICAL WAVE OVER THE BAY OF CAMPECHE ALONG 91W S OF 22N MOVING
W 15-20 KT.  THIS WAVE IS ALSO LOCATED FAIRLY CLOSE TO AN UPPER
LEVEL TROUGH THOUGH IT IS ON THE EAST SIDE OF THAT FEATURE.
SCATTERED TSTMS S OF WITHIN 90 NM OF THE YUCATAN PENINSULA FROM
87W-91W OVER GULF WATERS WERE LIKELY AIDED BY THE WAVE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N13W 7N27W 11N39W 11N44W 9N50W
9N55W.  A SQUALL LINE IS EMERGING FROM W AFRICA WITHIN 60 NM OF
THE COAST FROM 6N TO 11.5N.  ISOLATED MODERATE CONVECTION FROM
4N-8.5N BETWEEN 25W-33W.  SIMILAR CONVECTION WITHIN 60 NM OF
AXIS FROM 35W-48W.

...DISCUSSION...

GULF OF MEXICO...
RELATIVELY DRY AIR...ESPECIALLY FOR MID-SEPTEMBER... IN THE
LOW/MID LEVELS CONTINUES OVER THE NORTHERN GULF EAST OF
LOUISIANA...ALL THE WAY THRU NAPLES FLORIDA AND WESTWARD TO LAKE
CHARLES INTO THE CENTRAL GULF TO 26N.  THIS TREAT IS A GIFT FROM
NEARLY-STATIONARY OPHELIA WHICH IS MOSTLY RESPONSIBLE FOR THE
CONTINUED CONTINENTAL AIR POURING SOUTHWARD.  A FEW TSTMS ARE
OVER S FLORIDA... WITH WIDELY SCATTERED ACTIVITY WITHIN 120 NM
OF THE COAST IN S TEXAS AND A FEW SHOWERS OFFSHORE... OTHERWISE
DRY WEATHER IS THE RULE.  IN THE UPPER LEVELS... LOW IS NEAR
27N92.5W S OF LOUISIANA TROUGHING SWD TO THE BAY OF CAMPECHE.
UPPER RIDGING IS BUILDING INTO THE SE GULF AND IS STATIONARY
OVER SE TEXAS.  INCREASING RAIN CHANCES ARE LIKELY FOR THE SW
GULF S OF 24N W OF 90W DURING THE NEXT FEW DAYS AS MOISTURE
INCREASES ON THE E SIDE OF THE UPPER TROUGH AXIS.  OTHERWISE
HIGH PRESSURE IS FORECAST TO BUILD INTO THE CENTRAL GULF WITH
SMALL CHANCES OF RAIN IN S TEXAS AND EXTREME S FLORIDA.

CARIBBEAN...
AN UPPER LEVEL HIGH IS CENTERED NEAR W CUBA WITH A SHARP RIDGE
AXIS SWD TO CENTRAL NICARAGUA. UPPER DIFFLUENCE IS LOCATED
BENEATH THE RIDGE ON THE SIDE SIDE AND IS ENHANCING WIDELY
SCATTERED MODERATE CONVECTION FROM 16N-19N BETWEEN 83W-85W.
TYPICAL TSTMS ARE IN THE FAR SW CARIBBEAN NEAR 11N80W ...
OTHERWISE AN INVERTED TROUGH RUNS FROM 11N78W TO THE WINDWARD
PASSAGE.  EASTERN CUBA SHOULD STAY A LITTLE WETTER THAN AVERAGE
DUE TO UPPER LIFT FROM THE TROUGH WITH CENTRAL AMERICA FAIRLY
WET S OF HONDURAS.  IN THE E CARIBBEAN... ELY FLOW DOMINATES
FROM A MID/UPPER HIGH NEAR 20N65W.  VERY DRY AIR ALOFT CONTROLS
THE SE CARIBBEAN WITH FEW SHOWERS S OF 13N.  FARTHER TO THE N...
OCCASIONALLY SURGES OF LOW-LEVEL MOISTURE ARE RESPONSIBLE FOR
ISOLATED SHOWERS IN THE LEEWARD ISLANDS WESTWARD TO PUERTO RICO.
MOISTURE FROM THE TAIL END OF A DISSIPATING FRONTAL BOUNDARY
SHOULD INCREASE RAIN CHANCES FOR THE LEEWARDS TOMORROW THRU
PUERTO RICO BY WED.  SOME SMALL INCREASE IN RAIN IS POSSIBLE IN
THE WINDWARD ISLANDS BY LATE WED AS DEEPER-LAYERED MOISTURE
MOVES INTO THE AREA.

ATLANTIC...
TROPICAL STORM OPHELIA IS CENTERED JUST N OF THE AREA NEAR THE
SOUTH CAROLINA COAST AND IS DRAGGING DRY AIR SWD OVER FLORIDA
AND JUST N OF THE BAHAMAS. A SURFACE TROUGH EXTENDS S OF OPHELIA
FROM 30N72W TO JUST E OF ANDROS ISLAND BUT IS ONLY PRODUCING
JUST A FEW TSTMS.  UPPER RIDGING IS ORIENTED FROM SE TO NW WITH
ONE CENTER JUST N OF PUERTO RICO AND ANOTHER JUST E OF THE
STORM.  THE OTHER FEATURE OF NOTE IS A VERY STRONG TROUGH OVER
THE CENTRAL ATLC THAT HAS DRIVEN A COLD FRONT FAR TO THE SOUTH
FOR SEPT... FROM 31N44W 26N50W 25N56W THEN STATIONARY NW TO
31N65W.  THE MAIN UPPER ENERGY IS WELL NE OF THE FRONTAL
BOUNDARY SO ONLY A ISOLATED TSTMS WITH AN OCCASIONAL TSTMS
WITHIN 60 NM OF THE FRONT.  1022 MB HIGH IS JUST N OF BERMUDA
BRINGING DEWPOINTS IN THE LOWER 60S IN THE AREA.  FARTHER E...
A STATIONARY FRONT LIES INS THE E-CENTRAL ATLC ALONG 31N34W
23N50W.  EARLIER TSTMS HAVE DISSIPATED WITH A FEW SHOWERS ONLY
REMAINS.  THIS FEATURE SHOULD BECOME BY THE APPROACHING STRONG
COLD FRONT TO THE NW.  A MID/UPPER LEVEL LOW IS LOCATED OVER THE
CENTRAL TRPCL ATLC NEAR 19N46W AND IS PUTTING MODERATE SWLY
SHEAR OVER THE TROPICAL WAVE NEAR 45W...PLACING THE CONVECTION
MOSTLY E OF THE WAVE AXIS.  PUSHING ALL THE SHOWER ACTIVITY
FARTHER E. FARTHER E...UPPER HIGH IS NEAR 33N30W WITH ANOTHER
DEEP TROUGH DIGGING IN FROM SW PORTUGAL THRU THE W CANARY
ISLANDS TO 25N24W.  UPPER RIDGING IS ALONG 33W IN THE TROPICAL
ATLC WITH MOST CONVECTION LIMITED TO THE ITCZ.

$$
BLAKE

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