[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 230551
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU OCT 23 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 26W S OF 14N MOVING W 5-10 KT. THIS
WAVE IS NOT PARTICULARLY WELL-DEFINED...AND DRY AIR EMBEDDED
WITHIN THE BASE OF AN UPPER TROUGH IN THE E ATLC N OF 11N E OF
38W IS SUPPRESSING CONVECTIVE DEVELOPMENT NEAR THE WAVE.
HOWEVER...CIMSS WAVETRAK PRODUCT DEPICTS A WEAK AND DISORGANIZED
AREA OF LOW LEVEL COUNTERCLOCKWISE CIRCULATION PRESENT NEAR WAVE
AXIS. ISOLATED MODERATE CONVECTION IS OCCURRING WITHIN 150 NM
EITHER SIDE OF WAVE AXIS S OF 11N...LIKELY BEING ENHANCED BY LOW
LEVEL CONVERGENCE NEAR THE ITCZ.

A TROPICAL WAVE IS ALONG 52W/53W S OF 20N MOVING W 5-10 KT. A
RECENT ASCAT PASS DEPICTS COUNTERCLOCKWISE CURVATURE IN THE
SURFACE WIND FIELD IN THE VICINITY OF THE WAVE AXIS. THIS WAVE
IS NEARLY ALIGNED WITH A SURFACE TROUGH TO THE NORTH THAT
EXTENDS FROM 30N50W TO 22N52W. THIS WAVE COINCIDES WITH A DEEP
LAYER MOISTURE MAXIMUM BASED ON TOTAL PRECIPITABLE WATER PRODUCT
FROM CIMSS. THIS MOISTURE IS BEING DRAWN NORTHWARD OVER THE E
PORTIONS OF AN UPPER TROUGH OVER THE CENTRAL ATLC FROM 17N-31N
BETWEEN 48W-63W. ISOLATED MODERATE CONVECTION IS WITHIN 150 NM
EITHER SIDE OF WAVE AXIS S OF 14N...LIKELY BEING ENHANCED BY LOW
LEVEL CONVERGENCE NEAR THE ITCZ.

A TROPICAL WAVE IS ALONG 82W S OF 18N MOVING W 10-15 KT. THIS
WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE...AS WELL
AS A MAXIMUM IN LOW LEVEL COUNTERCLOCKWISE CIRCULATION BASED ON
CIMSS WAVETRAK PRODUCT. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS OCCURRING WITHIN 210 NM EITHER SIDE OF WAVE AXIS
FROM 12N-15N. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS
FROM 16N-19N BETWEEN 80W-83W...WHICH IS LIKELY BEING ENHANCED BY
UPPER LEVEL DIFFLUENCE TO THE W OF AN UPPER HIGH IN THE CENTRAL
CARIBBEAN NEAR 17N79W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 10N22W 8N36W 11N50W 9N61W. IN
ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES...
SCATTERED MODERATE CONVECTION IS FROM 3N-9N BETWEEN 10W-17W...
AFFECTING W PORTIONS OF GUINEA-BISSAU. ISOLATED MODERATE
CONVECTION IS WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 19W-23W.
ISOLATED MODERATE CONVECTION IS WITHIN 180 NM EITHER SIDE OF
AXIS FROM 29W-50W. SIMILAR CONVECTION IS FOUND WITHIN 150 NM N
OF AXIS BETWEEN 55W-61W.

...DISCUSSION...

GULF OF MEXICO...
MUCH OF THE GULF IS COVERED BY INCREASING SOUTHWESTERLY FLOW
ALOFT...AS A VIGOROUS UPPER TROUGH OVER THE SOUTHERN PLAINS OF
THE CONUS CONTINUES TO APPROACH THE GULF. AT THE SAME
TIME...DEEP MOISTURE IS ROTATING NORTHEASTWARD AROUND AN UPPER
HIGH IN THE CENTRAL CARIBBEAN NEAR 17N79W. UPPER LEVEL
DIFFLUENCE TO THE N OF THIS UPPER HIGH IS SUPPORTING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS OVER THE E GULF S OF 27N E OF
87W...AFFECTING S PORTIONS OF FLORIDA AND W CUBA. THIS ACTIVITY
IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH
THAT EXTENDS FROM A 1010 MB SURFACE LOW OVER NE BELIZE NEAR
18N88W TO THE N YUCATAN PENINSULA NEAR 22N87W TO THE SE GULF
NEAR 24N83W. COMPUTER MODEL GUIDANCE SUGGESTS THAT STRONG UPPER
LEVEL DIVERGENCE SE OF A MID/UPPER-LEVEL WIND SPEED MAXIMUM
ROTATING AROUND THE AFOREMENTIONED VIGOROUS UPPER TROUGH WILL
HELP TO CONCENTRATE THE SURFACE TROUGH AND SURFACE LOW OVER THE
NE GULF...WITH A LOW EXPECTED IN THE NE GULF OVER THE NEXT DAY.
ALSO...A COLD FRONT ASSOCIATED WITH THE VIGOROUS UPPER TROUGH IS
APPROACHING THE NW GULF...WITH INCREASED NORTHERLY SURFACE WINDS
IN THE WAKE OF THE FRONT. ADDITIONALLY...A SURFACE TROUGH OVER
THE W GULF EXTENDS FROM 28N95W TO A 1011 MB SURFACE LOW NEAR
23N94W TO 21N92W. LOW LEVEL CONVERGENCE NEAR THESE FEATURES IS
RESULTING IN ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE
SURFACE TROUGH.

CARIBBEAN SEA...
A SURFACE TROUGH IS OVER THE W CARIBBEAN AND EXTENDS FROM A
1010 MB SURFACE LOW OVER NE BELIZE NEAR 18N88W TO THE N YUCATAN
PENINSULA NEAR 22N87W TO THE SE GULF NEAR 24N83W. BROAD LOW
LEVEL CONVERGENCE AROUND THESE FEATURES...COMBINED WITH AMPLE
DEEP LAYER MOISTURE AND UPPER LEVEL DIVERGENCE TO THE W OF THE
UPPER HIGH IN THE CENTRAL CARIBBEAN NEAR 17N79W...IS RESULTING
IN ISOLATED MODERATE CONVECTION IN THE NW CARIBBEAN FROM 21N-23N
BETWEEN 82W-87W...INCLUDING W CUBA. ALSO...NUMEROUS
MODERATE/SCATTERED STRONG CONVECTION FROM 16N-19N BETWEEN
80W-83W IS LIKELY RESULTING FROM THE INTERACTION OF UPPER LEVEL
DIFFLUENCE W OF THE UPPER HIGH AND THE TROPICAL WAVE ALONG 82W S
OF 18N. ALSO...SCATTERED MODERATE/ISOLATED STRONG CONVECTION
OVER NICARAGUA AND COSTA RICA IS IMPACTING THE NEARBY CARIBBEAN
WATERS. THIS CONVECTION IS BEING ENHANCED BY GREATER INSTABILITY
OVER HIGHER TERRAIN. TO THE E OF THE AFOREMENTIONED UPPER
HIGH...DEEP LAYER DRY AIR AND STABLE ATMOSPHERIC CONDITIONS ARE
INHIBITING DEEP CONVECTION OVER THE E CARIBBEAN.

ATLANTIC OCEAN...
THE FLOW AROUND THE UPPER HIGH IN THE CENTRAL CARIBBEAN NEAR
17N79W IS BRINGING DEEP MOISTURE INTO THE SW ATLC...WITH
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 27N W OF
71W...AFFECTING S PORTIONS OF FLORIDA AND E CUBA. FARTHER TO THE
E...A DEEP LAYER TROUGH IS OVER THE CENTRAL ATLC FROM 17N-31N
BETWEEN 48W-63W...AND IS SUPPORTING A SURFACE TROUGH THAT
EXTENDS FROM 30N50W TO 22N52W. DEEP LAYER MOISTURE OVER E
PORTIONS OF THE DEEP LAYER TROUGH IS ENHANCING SCATTERED
MODERATE CONVECTION FROM 22N-24N BETWEEN 50W-52W. FARTHER TO THE
E...AN UPPER RIDGE AXIS EXTENDS FROM 35N38W TO 24N42W TO
15N45W...AND AN UPPER TROUGH IS IN THE E ATLC N OF 11N E OF 38W.
GENERALLY DEEP LAYER DRY AIR IS PREVENTING DEEP CONVECTION NEAR
THESE FEATURES. ADDITIONALLY...A 1030 MB SURFACE HIGH IS
CENTERED NEAR 38N22W...AND A SURFACE RIDGE EXTENDS FROM THIS
SURFACE HIGH TO THE SW NEAR 16N40W...WITH SUBSIDENCE AND STABLE
CONDITIONS AROUND THESE FEATURES RESULTING IN GENERALLY FAIR
WEATHER CONDITIONS ACROSS MUCH OF THE E ATLC.

$$
COHEN

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