[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171816
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE JUL 17 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE HAS BEEN ADDED ALONG 24W EXTENDING THROUGH THE
CAPE VERDE ISLANDS. A 1010 MB LOW IS ALONG THE WAVE AXIS NEAR
15N MOVING W NEAR 18 KT. THE DAKAR RAOB SHOWED THE WAVE PASSAGE
WELL YESTERDAY MORNING. NO DEEP CONVECTION IS IN THE VICINITY OF
THE LOW...THOUGH SCATTERED MODERATE/ISOLATED STRONG IS EMBEDDED
IN THE ITCZ FROM 9N-12N BETWEEN 20W-24W.

TROPICAL WAVE IS ALONG 47W/48W S OF 17N. THIS WAVE WAS ADJUSTED
SLIGHTLY TO THE E TO COINCIDE WITH THE MOST POLEWARD INFLECTION
OF THE ITCZ...WHICH ALSO MESHES UP WELL WITH THE CREST OF HIGHER
MOISTURE AS DENOTED BY THE UW-CIMSS SSMI DERIVED TOTAL
PRECIPITABLE WATER PRODUCT. THIS WAVE PASSED DAKAR EARLY ON JULY
12 WHICH IMPLIES AN OVERALL WWD MOTION OF 6 DEGREES PER DAY...OR
15 KT. SCATTERED MODERATE CONVECTION IS WITHIN 150NM EITHER SIDE
OF THE AXIS FROM 5N-9N. THE WAVE MAY ALSO BE ENHANCING THE
CONVECTION ALONG THE ITCZ FURTHER W AS DESCRIBED BELOW.

TROPICAL WAVE IS OVER THE CARIBBEAN ALONG 75/76W S OF 20N MOVING
W 15-20 KT. THIS WAVE MAY NEED TO BE NUDGED FURTHER W AS PER THE
WWD MOVING SURGE OF SHOWERS AND TSTMS MOVING INTO THE WRN
CARIBBEAN BETWEEN 77W-84W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N16W 10N22W 7N35W 11N45W 11N50W
6N58W. ISOLATED MODERATE CONVECTION IS WITHIN 60NM N AND 120NM S
OF THE AXIS E OF 20W. IN ADDITION...A SMALL CLUSTER OF STRONG
CONVECTION IS MOVING OFF THE AFRICAN COAST NEAR 14N17W.
SCATTERED MODERATE WITHIN 90NM EITHER SIDE OF AXIS BETWEEN
38W-42W. NUMEROUS MODERATE...POSSIBLY ENHANCED BY THE
APPROACHING TROPICAL WAVE...IS WITHIN 150 NM N/30NM S OF THE
AXIS W OF 49W.

...DISCUSSION...
GULF OF MEXICO...
THE MOST ACTIVE WEATHER IN THE GULF THIS AFTERNOON LIES IN THE
WRN PORTION JUST OFF THE TEXAS/MEXICO COAST. LIGHTNING DATA
SUPPORTS SCATTERED TO NUMEROUS TSTMS N OF 20N W OF 92W. THIS
ACTIVITY IS BEING SUPPORTED BY DIFFLUENCE AHEAD OF THE MID TO
UPPER LEVEL LOW/TROUGH OVER NE MEXICO. IN ADDITION...SOME SUBTLE
LOW LEVEL CONFLUENCE NOTED IN SATELLITE IMAGERY AND THIS
MORNINGS QUIKSCAT PASS. DEBRIS MOISTURE OVER THIS CONVECTION IS
SPREADING NE N OF 23N WITH UPPER SW FLOW...AND TO THE E/SE S OF
23N AROUND RIDGING. ELSEWHERE...A FEW ISOLATED SHOWERS/TSTMS
NOTED IN THE FAR SE GULF. ON THE LARGE SCALE AT THE SFC...THE
WRN PORTION OF AN ATLC SFC RIDGE CONTINUES TO DOMINATE AND IS
GENERALLY EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS.

CARIBBEAN SEA...
SCATTERED SHOWERS/ISOLATED TSTMS ARE MOVING INTO THE WRN
CARIBBEAN AND CENTRAL AMERICA BETWEEN 78W-85W. THIS ACTIVITY IS
BEING SUPPORTED BY UPPER DIFFLUENCE SW OF AN UPPER LOW BETWEEN
JAMAICA AND ERN CUBA AND LOW LEVEL SPEED CONVERGENCE. FURTHER
UPPER DIFFLUENCE BETWEEN THE UPPER LOW AND UPPER RIDGING OVER
THE ERN CARIBBEAN IS ALSO SUPPORTING THE SCATTERED MODERATE
CONVECTION NEAR PUERTO RICO AND ADJACENT WATERS FROM 18N-21N
BETWEEN 65W-70W. OTHERWISE MODERATE TO FRESH TRADES ARE IN PLACE
ON THE SW PORTION OF AN ATLC SFC RIDGE AND EXPECTED TO PERSIST
OVER THE NEXT COUPLE OF DAYS. UW-CIMSS SAHARAN AIR LAYER PRODUCT
DEPICTS FAIRLY DENSE REGION OF AFRICAN DUST OVER THE E/CENTRAL
CARIBBEAN. THE DUST MAY HAVE BEEN WHY ST. CROIX WAS REPORTING
HAZE EARLIER THIS MORNING.

ATLANTIC OCEAN...
ISOLATED TSTMS ARE OVER THE FAR WRN ATLC W OF 77W UNDERNEATH AN
UPPER HIGH. OVERALL THOUGH SFC RIDGING DOMINATES SW OF A 1030 MB
HIGH PRES CENTER NEAR 35N49W. INVERTED SFC TROUGHING EMBEDDED IN
THIS RIDGE IS ALONG 29N58W 23N61W 20N66W. THIS...ALONG WITH LIFT
AHEAD OF THE MID TO UPPER LOW NEAR 29N63W...IS SUPPORTING
SCATTERED SHOWERS/ISOLATED TSTMS N OF 20N BETWEEN 56W-63W. THE
ACTIVITY NEAR PUERTO RICO IS DESCRIBED IN CARIB SECTION. THE
AREA N OF 18N AND E OF 55W IS WIDELY DOMINATED BY FAIR
WEATHER...SCATTERED LOW TO MID CLOUDS AND MODERATE TRADES. AN
UPPER RIDGE AXIS IS EXTENDING N ALONG 55W WITH ANOTHER UPPER
RIDGE OVER THE FAR ERN ATLC IN BETWEEN IS A WEAK UPPER TROUGH N
OF 19N BETWEEN 35W-45W. DENSE AREA OF AFRICAN DUST NOTED OVER
MUCH OF THE AREA E OF 40W.

$$
WILLIS






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