Atlantic Tropical Weather Discussion

000
AXNT20 KNHC 021731
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUL 02 2009

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...TROPICAL WAVES...

A LARGE TROPICAL WAVE IS ALONG 28W/29W S OF 17N MOVING W NEAR 20 
KT. THIS WAVE IS VERY BROAD WITH VISIBLE SATELLITE IMAGES 
INDICATING AN AREA OF CYCLONIC TURNING COVERING NEARLY A 1000 NM 
AREA. THE AXIS IS PLACED ROUGHLY IN THE CENTER OF THE CYCLONIC 
ENVELOPE WHERE CLOUD DRIFT WINDS SUGGEST A VORTICITY MAXIMUM 
NEAR 10N29W. SYNOPTIC PRESSURE OBSERVATIONS FROM THE CAPE VERDE 
ISLANDS SHOW A 3 MB PRESSURE INCREASE OVER THE PAST 24 
HOURS...INDICATIVE OF THE WAVE PASSAGE. QUIKSCAT DATA REVEALS NE 
20-25 KT WINDS W OF THE AXIS N OF 14N DUE TO THE TIGHTENED 
PRESSURE GRADIENT BETWEEN THE WAVE AND THE SUBTROPICAL RIDGE. 
CONVECTION IS FAIRLY LIMITED AND CONFINED TO THE INTERSECTION OF 
THE ITCZ. 

A TROPICAL WAVE HAS BEEN ADJUSTED W TO ALONG 47W/48W S OF 16N 
MOVING W 15-20 KT. THE ADJUSTMENT IN POSITION WAS BASED ON AN 
INVERTED V-SHAPE IN THE LOW-LEVEL CLOUD FIELD WHICH AGREES WITH 
A MAXIMUM IN TOTAL PRECIPITABLE WATER. THE INTERACTION WITH AN 
UPPER LOW TO ITS W IS FUELING SCATTERED MODERATE CONVECTION FROM 
9N-11N BETWEEN 49W-52W.   

A TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 70W/71W S OF 
17N MOVING W 15-20 KT. VISIBLE IMAGES SHOW SLIGHT CYCLONIC 
TURNING IN THE LOW-LEVEL CLOUDS. ONE SMALL PATCH OF ENHANCED 
CLOUDINESS IS APPARENT NEAR THE N PORTION OF THE WAVE FROM 
16N-17N BETWEEN 70W-72W...ENHANCED BY INSTABILITY ALONG AN E-W 
UPPER TROUGH AXIS.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 9N27W 7N38W 6N46W 7N59W. 
SCATTERED MODERATE CONVECTION IS FROM 4N-11N BETWEEN 24W-37W. 
SCATTERED MODERATE CONVECTION IS FROM 3N-7N BETWEEN 49W-54W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYER TROUGH IS OVER THE EASTERN U.S. EXTENDING INTO THE 
N GULF. DEEP LAYER SW-W FLOW IS SUPPORTING SCATTERED SHOWERS AND 
TSTMS FROM 26N-28N E OF 94W. UPPER DIFFLUENCE BETWEEN A HIGH 
OVER W MEXICO AND AN UPPER LOW IN THE CARIBBEAN IS ENHANCING 
SCATTERED MODERATE CONVECTION OVER THE SRN BAY OF CAMPECHE. 
GENERALLY LIGHT S-SW SFC WINDS EXIST ACROSS THE AREA BETWEEN THE 
ATLC SUBTROPICAL RIDGE AND A FRONT OVER THE SE U.S. THIS FRONT 
IS EXPECTED TO GRADUALLY WEAKEN OVER THE NEXT COUPLE OF DAYS AS 
THE LOW MOVES NE ALLOWING SFC RIDGING TO BUILD W ACROSS THE GULF.

CARIBBEAN SEA...
ACROSS THE W CARIBBEAN...AN UPPER LEVEL LOW IS CENTERED NE OF 
HONDURAS NEAR 15N83W WITH AN ASSOCIATED UPPER LEVEL TROUGH 
EXTENDING SOUTHWARD TO COSTA RICA. ASSOCIATED ATMOSPHERIC 
INSTABILITY IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS 
ACROSS THE SW CARIBBEAN S OF 12N W OF 77W INCLUDING PORTIONS OF 
COSTA RICA AND PANAMA. ACROSS THE NW CARIBBEAN...DEEP LAYER DRY 
AIR AND SUBSIDENCE IN NORTHERLY FLOW ALOFT W OF THE UPPER LOW IS 
SUPPORTING GENERALLY FAIR WEATHER. ACROSS THE E CARIBBEAN...A 
BROAD UPPER LEVEL RIDGE IS PRESENT. DEEP LAYER DRY AIR AND 
ATMOSPHERIC STABILITY ASSOCIATED WITH THIS UPPER LEVEL HIGH IS 
RESULTING IN GENERALLY FAIR WEATHER ACROSS THE E CARIBBEAN. THE 
SURFACE PRESSURE GRADIENT S OF A SURFACE RIDGE OVER THE CENTRAL 
AND E ATLC IS SUPPORTING NE TO E WINDS OF 20 TO 30 KT...HIGHEST 
NEAR THE COAST OF COLOMBIA.

ATLANTIC OCEAN...
ACROSS THE SW NORTH ATLC...ATMOSPHERIC LIFT IN SOUTHWESTERLY 
ALOFT IS INTERACTING WITH DEEP LAYER MOISTURE TO SUPPORT 
SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 90 NM EITHER SIDE OF 
A LINE FROM 32N73W TO 27N80W INCLUDING THE NW BAHAMAS. TO THE 
E...DEEP LAYER MOISTURE STREAMING AROUND AN UPPER LEVEL HIGH 
CENTERED NEAR 27N70W IS SUPPORTING SCATTERED SHOWERS AND 
ISOLATED THUNDERSTORMS N OF 27N BETWEEN 43W-52W. FARTHER TO THE 
E...GENERALLY FAIR WEATHER IS PRESENT ACROSS MUCH OF THE CENTRAL 
AND E ATLC...WHERE SUBSIDENCE IS OCCURRING NEAR A BROAD SURFACE 
RIDGE. THIS SURFACE RIDGE IS ASSOCIATED WITH A 1025 MB SURFACE 
HIGH NEAR 27N58W AND A 1026 MB SURFACE HIGH NEAR 31N27W. 
HOWEVER...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM AN UPPER LEVEL 
LOW NEAR 31N37W TO 22N42W. A BROAD AREA OF LOW/MID-LEVEL DRY 
SAHARAN AIR COVERS THE E ATLC S OF 25N TO THE ITCZ E OF 55W AND 
IS LIMITING THE AREAL COVERAGE OF DEEP CONVECTION IN THIS AREA. 
ALSO...AN UPPER LEVEL HIGH OVER THE TROPICAL ATLC CENTERED NEAR 
10N36W IS ENHANCING CONVECTION NEAR THE ITCZ. 

$$
COHEN/CANGIALOSI