[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121049
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI AUG 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURE...

TROPICAL STORM IRENE IS CENTERED NEAR 27.6N 65.4W...OR 690 NM SE
OF CAPE HATTERAS NORTH CAROLINA...AT 12/0900 UTC MOVING NW AT
13 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM
SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. SEE THE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. UPPER LEVEL OUTFLOW IS
EXPANDING IN ALL BUT THE SW QUADRANT. THE LOW LEVEL CENTER IS
NOT WELL-DEFINED ON INFRARED SATELLITE IMAGERY BUT WAS
DETERMINED TO TH EAST OF THE PREVIOUS ADVISORY POSITION WITH
MICROWAVE SATELLITE PASSES. CLOUD TOPS REMAIN NEARLY THE SAME
ALTHOUGH THE SYSTEM IS STRENGTHENING. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 26N-30.5N BETWEEN 63W-67.5W.

...TROPICAL WAVES...

TROPICAL WAVE IS JUST OFF THE AFRICAN COAST ALONG 19W/20W S OF
21N MOVING W 5-10 KT WITH A 1010 MB LOW ALONG THE WAVE 16N. WAVE
IS UNDER THE W EDGE OF AN UPPER HIGH THAT IS INLAND OVER
AFRICA...PARTIALLY OBSCURING THE SATELLITE SIGNATURE WITH ONLY
SCATTERED SHOWERS W OF THE W TO THE COAST OF AFRICA.

TROPICAL WAVE IS ALONG 39W S OF 16N MOVING W 15-20 KT. WAVE
PRESENTS A LOW AMPLITUDE LOW LEVEL SIGNATURE WITH THE MID LEVEL
FLOW MORE PRONOUNCED. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION ARE IN AN INVERTED-V PATTERN WITHIN 60/75 NM
OF LINE FROM 11N38W PEAKING NEAR 12N41W TO 10N44W.

TROPICAL WAVE IS ALONG 54W S OF 16N MOVING W 15 KT. THIS WAVE
CONTINUES NOT TO BE VERY WELL-DEFINED AND ACTUALLY APPEARS TO BE
ASSOCIATED WITH AN EASTERLY WIND SURGE...WHOSE LEADING EDGE IS
NEAR THE W AXIS. DRY AIR AT ALL LEVELS LENDS THAT THERE IS NO
ASSOCIATED CONVECTION WITH THIS WAVE.

E CARIBBEAN TROPICAL WAVE ALONG 67W S OF 19N MOVING W 10-15 KT.
WAVE IS EMBEDDED WITHIN WEAK FLOW S OF T.S. IRENE WITH AN EVEN
WEAKER INVERTED-V SIGNATURE NOTED ON THE INFRARED SATELLITE
IMAGERY BETWEEN THE VIRGIN AND ABC ISLANDS. ASSOCIATED DEEP
CONVECTION IS INLAND OVER SOUTH AMERICA.

W CARIBBEAN TROPICAL WAVE IS ALONG 87W S OF 20N MOVING W 10-15
KT. WAVE IS BENEATH AN UPPER HIGH LOCATED OVER CENTRAL AMERICA
WHICH IS ENHANCING SCATTERED MODERATE TO STRONG CONVECTION OVER
THE AREA S OF 18N W OF 86W...MOSTLY OVER THE YUCATAN PENINSULA.

...ITCZ...
ITCZ AXIS CENTERED ALONG 14N21W 11N33W 11N62W. WIDELY
SCATTERED CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN
120 NM OF LINE FROM 10N22W 8N35W TO 12N53W.

...DISCUSSION...

GULF OF MEXICO...
CUT-OFF MID/UPPER LOW THAT HAS DOMINATED THE GULF THIS WEEK IS
ALONG THE N GULF COAST NEAR MISSISSIPPI WITH A TROUGH AXIS
EXTENDING SW TO THE COAST OF MEXICO TAMPICO. THIS IS ADVECTING
TROPICAL MOISTURE ACROSS S MEXICO NE ACROSS THE YUCATAN
PENINSULA INTO THE SE GULF BRINGING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS S OF 27N E OF 88W ACROSS S FLORIDA. IN ADDITION...
A WEAK 1015 MB LOW IS FORMING JUST OFF THE COAST OF MISSISSIPPI
WITH A SURFACE TROUGH STRETCHES W TO OFF THE W LOUISIANA COAST.
THIS IS GENERATING SCATTERED SHOWERS/THUNDERSTORMS ALONG THE
COAST OF LOUISIANA COAST FROM THE MISSISSIPPI DELTA TO
ATCHAFALAYA BAY. THUNDERSTORMS OVER THE S MEXICO ARE MOVING W
ALONG THE IMMEDIATE COAST IN THE THE BAY OF CAMPECHE W OF 93W.
DEEP MOISTURE WILL BE MOSTLY LIMITED OVER THE AREA INTO THE
WEEKEND...SO ANY THUNDERSTORM ACTIVITY SHOULD BE MAINLY OVER
LAND AREAS WHERE HEATING IS GREATEST.

CARIBBEAN...
MID/UPPER LEVEL HIGH IS OVER CENTRAL AMERICA W TO SW FLOW OVER
THE W CARIBBEAN W OF 81W. THIS COUPLED WITH AN UPPER TROUGH
STRETCHING ACROSS CUBA TO TO OVER PANAMA IS GIVING W CARIBBEAN
DRY SUBSIDING AIR FROM 74W-83W AND MOSTLY FAIR WEATHER TO THE
DEEP CARIBBEAN WATERS. SCATTERED THUNDERSTORMS ARE MOVING
OFFSHORE THE COASTS OF CUBA AND HAITI WITH SCATTERED
MODERATE/STRONG CONVECTION AT THE BASE OF THE UPPER TROUGH S OF
11N TO INLAND OVER PANAMA. MID/UPPER HIGH OVER THE CENTRAL ATLC
EXTENDS INTO THE E CARIBBEAN N OF 11N E OF 67W WHICH IS DRYING
THE UPPER AIR OVER MOST OF THE AREA EXCEPT OVER THE THE LESSER
ANTILLES WHERE SCATTERED SHOWERS/THUNDERSTORMS ARE FROM 12N-17N
BETWEEN 58W-64W. THIS MOISTURE WILL HANG AROUND THE E CARIBBEAN
THROUGH SAT BEFORE ANOTHER SURGE OF DRY AIR ENTERS THE AREA FROM
THE NE.

ATLANTIC...
SHARP MID/UPPER RIDGE AXIS EXTENDS S ALONG THE E FLORIDA COAST
TO OVER CUBA. WEAK UPPER LOW NE OF THE BAHAMAS NEAR 26N75W
EXTENDS AN UPPER TROUGH ACROSS CUBA INTO THE CARIBBEAN. THIS IS
BRINGING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ALONG THE
COAST OF FLORIDA TO CUBA W OF 78W. A DIGGING DEEP LAYERED TROUGH
IS TO THE E OF T.S. IRENE WITH THE AXIS EXTENDING THROUGH 32N35W
SW ALONG 28N44W TO A BASE NEAR 21N52W. THE UPPER TROUGH IS
PUSHING A WEAKENING COLD FRONT TO THE SE ALONG 32N31W 29N35W
30N42W TO A 1020 MB LOW AT THE END OF THE FRONT NEAR 29N44W AND
A WEAK SURFACE TROUGH EXTENDING SW TO 25N49W. BROAD SW MID/UPPER
LEVEL FLOW IS AHEAD OF THE TROUGH OVER THE REMAINDER OF THE
SUBTROPICS...WITH DRY AIR E OF 40W TO THE AFRICAN COAST. FARTHER
S...MID/UPPER LEVEL HIGH IS LOCATED SE OF T.S. IRENE...AND NE OF
THE LEEWARD ISLANDS NEAR 22N59W. A CONVERGENCE LINE EXTENDS SE
OF IRENE AND HAS TRIGGERED SCATTERED MODERATE CONVECTION FROM
12N-17N BETWEEN 58W-64W. DEEP EASTERLY FLOW EXTENDS ACROSS MOST
OF THE TROPICAL ATLC WITH THE EXCEPTION OF THE FAR E ATLC WHERE
A WEAK MID/UPPER LEVEL LOW IS JUST S OF THE CAPE VERDE ISLANDS.
THIS LOW HAS FORCED DRY AIR TO PLUNGE S TO 11N WHILE ALLOWING
DEEPER MOISTURE TO EXPAND N TO THE W SAHARA/MOROCCO BORDER. THIS
SET-UP IS PROVIDING A FAVORABLY DIVERGENT ENVIRONMENT OF THE
TROPICAL WAVE WHICH RECENTLY MOVED OFF THE AFRICAN COAST.

$$
WALLACE



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