[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 051730
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUL 05 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
1715 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ADDED TO 12Z ANALYSIS HIGHLY TITLED ALONG 4N28W
11N26W 16N21W ESTIMATED TO BE MOVG W 10-15 KT. THE DAKAR UPPER
AIR TIME SECTION SHOWED A DISTINCT WAVE PASSAGE LATE JUNE
2ND/EARLY JUNE 3. THIS BROAD WAVE CONTAINS AN AREA OF LOW-LEVEL
TURNING IN THE VICINITY OF 10N27W WELL DEPICTED BY A PAIR OF
SURROUNDING SHIP OBS. IN ADDITION...THESE OBS ALSO INDICATE THAT
THERE IS SLIGHTLY LOWER PRES NEAR THE ANALYZED AXIS AS COMPARED
WITH SFC OBS TO IT'S E AND ALONG THE W AFRICAN COAST. A LARGER
SCALE INVERTED V-TYPE STRUCTURE IS APPARENT FURTHER TO THE
NE...WHICH WAS THE REASON FOR SLOPING THE WAVE IN THAT
DIRECTION. MINIMAL SHOWER ACTIVITY IS ASSOCIATED WITH THIS
FEATURE.

A 1014 MB LOW PRES SYSTEM CENTERED NEAR 11N49W IS MOVING W 10-15
KT. THIS WEAK LOW CONTINUES TO HAVE MINIMAL TSTM ACTIVITY
CONFINED TO THE SRN SEMICIRCLE. VIS IMAGERY TODAY HAS SHOWN THAT
THE CIRCULATION APPEARS OPEN AT TIMES...SO TO BETTER FIT THE
OVERALL STRUCTURE A TROPICAL WAVE WILL BE ADDED ALONG THE LOW AT
18Z.

THAT THE WEAK
LOW IS MORE ELONGATED AND MAY NOT BE ENTIRELY CLOSED ANY
LONGER...SO A TROPICAL WAVE WILL BE ADDED ALONG THE LOW AT 18Z
TO BETTER FIT THE OVERALL STRUCTURE OF THIS FEATURE.

A TROPICAL WAVE IS TITLED ALONG 61W/62W MOVING W NEAR 15 KT.
ASSOCIATED SCATTERED SHOWERS ARE OVER THE SRN WINDWARD ISLANDS
AND OVER PORTIONS OF LEEWARD ISLANDS. HOWEVER...DEEP MOISTURE
REMAINS LIMITED LIKELY CAPPED BY THE STRONGLY SUBSIDENT
ENVIRONMENT THAT IT IS ENTRENCHED IN. OVERALL...THE STRUCTURE OF
THE WAVE IS LESS DEFINED TODAY WITH THE PSN BASED MOSTLY A
PERTURBATION IN THE ITCZ AND 24-H PRES TENDENCIES.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 7N25W 4N36W 6N50W 8N60W.
SCATTERED SHOWERS AND TSTMS ARE WITHIN 120 NM S OF THE AXIS
BETWEEN 15W-22W AND WITHIN 90 NM N OF AXIS BETWEEN 30W-34W.

...DISCUSSION...
GULF OF MEXICO...
SHOWERS AND TSTMS CONTINUE TO AFFECT PORTIONS OF THE NW
GULF...LOUISIANA AND E TEXAS. THE COMBINATION OF UPPER
DIFFLUENCE...BETWEEN AN UPPER LOW OVER NRN MEXICO AND AN UPPER
HIGH OVER THE N CENTRAL GULF...AND A TROUGH OF LOW PRES ARE THE
CULPRITS IN PRODUCING THE ACTIVITY HERE OVER AT LEAST THE PAST
FEW DAYS. IN THE E GULF...A WEAK SFC TROUGH HANGS WSW FROM A
1015 MB LOW NEAR SARASOTA FLORIDA TO 26N87W. MOST OF THE
DYNAMICS PRODUCING TSTM ACTIVITY LIES OFF THE E COAST OF
FLORIDA...MORE ON THIS IN THE ATLC SECTION. TIGHTENED PRES
GRADIENT BETWEEN HIGH PRES OVER THE SE STATES AND LOWER PRES
OVER TEX/MEX IS PRODUCING MODERATE SELY WINDS ACROSS THE SW
GULF. THE UPPER FLOW IS PREDOMINATELY N-NELY CAUGHT BETWEEN AN
UPPER RIDGE OVER THE EPAC AND AN UPPER LOW OVER THE NW CARIB.
THIS FLOW IS ADVECTING BROKEN HIGH LEVEL CLOUDINESS ACROSS THE
BULK OF THE AREA.

CARIBBEAN SEA...
A SURGE OF DRY AIR ALOFT CONTINUES TO PROPAGATE W ACROSS THE
CARIB ADVECTED TO ABOUT 82W FROM THE TROPICAL ATLC. THIS STABLE
AIRMASS IS PROVIDING FAIR WEATHER ACROSS MUCH OF THIS REGION.
THE EXCEPTION IS OVER THE LESSER ANTILLES WHERE PATCHY SHOWER
ACTIVITY IS AFFECTING THE SRN WINDWARDS AND NRN LEEWARDS
ASSOCIATED WITH A TROPICAL WAVE IN THE VICINITY. THE UPPER
ATMOSPHERE IS MORE MOIST FURTHER W SUPPORTED BY AN UPPER LOW
SPINNING OVER GUATEMALA. BUT EVEN HERE...DEEP MOISTURE IS
CONFINED TO THE EXTREME SW CARIB AND OVER PANAMA...COSTA RICA
AND SRN NICARAGUA ENHANCED BY THE ITCZ. A SMALLER LESS DEFINED
UPPER LOW HAS BEEN NEARLY STATIONARY OVER THE PAST COUPLE DAYS
ABOVE THE WINDWARD PASSAGE. INSTABILITY NEAR THIS LOW PRODUCED A
BRIEF BURST OF CONVECTION THIS MORNING BUT THIS HAS COMPLETELY
FIZZLED WITH ONLY A FEW SHOWERS LEFTOVER. AT THE SFC...A 1058 Z
QSCAT PASS SHOWED A LARGE AREA OF 20-30 KT ELY TRADES ACROSS THE
REGION FROM 11N-18N...STRONGEST NEAR THE COAST OF COLOMBIA.

ATLANTIC OCEAN...
A STALLED FRONT CLIPS THE AREA ALONG 32N52W 30N65W WITH A WEAK
LOW POSSIBLY FORMING ALONG IT'S TAIL. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE WITHIN 60 NM EITHER SIDE. DECIDED TO MAKE
SOME CHANGES IN THE ANALYSIS AT 12Z...ESSENTIALLY BREAKING THE
PERSISTENT FRONT BETWEEN 65W AND 72W DUE TO EXTENSIVE SLYS
BLOWING IN THAT ZONE. A WARM FRONT RESUMES AT 29N72W AND
CONNECTS TO A 1016 MB LOW OVER CENTRAL FLORIDA. THIS FRONTAL
SYSTEM IS PRODUCING SCATTERED TO NUMEROUS SHOWERS AND TSTMS
ALONG AND OFF THE E COAST OF FLORIDA AND OVER THE NW BAHAMAS
FROM 26N-30N BETWEEN 74W-80W. FARTHER E...THERE HAS BEEN LITTLE
CHANGE OVER THE PAST FEW DAYS WITH RIDGING STILL DOMINATING BOTH
AT THE SFC AND ALOFT. THE SFC AZORES HIGH IS ANALYZED 1032 MB
NEAR 37N26W. THIS HIGH IS PRODUCING A LARGE AREA OF MODERATE
TRADES ACROSS THE ATLC. STRONG NLY WINDS ARE NEAR THE AFRICAN
COAST DUE TO THE TIGHTENING PRES GRADIENT BETWEEN THE HIGH AND
INVERTED TROUGHING OVER THE CONTINENT. A SERIES OF UPPER HIGHS
ARE PROVIDING A VERY STABLE AIRMASS ACROSS THE CENTRAL AND E
ATLC WITH ONLY LOW-LEVEL STABLE STRATOCUMULUS CLOUDS SEEN ACROSS
MUCH OF THE BASIN.

$$
CANGIALOSI




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