[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 100013
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON JUL 09 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2330 UTC.

...TROPICAL WAVES...
A NEW TROPICAL WAVE IS INTRODUCED IN THE EASTERN ATLC ALONG
20W SOUTH OF 14N MOVING W AT 15 KT. THE WAVE SHOWS UP
PROMINENTLY IN SATELLITE IMAGERY AS WELL AS ANIMATED SSMI
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS
EVIDENT WHERE THE WAVE INTERSECTS THE ITCZ FROM 8N TO 10N
BETWEEN 18W AND 21W. THIS TROPICAL WAVE WILL BE ADDED ON THE 00Z
SURFACE ANALYSIS MAP.

AN ATLANTIC OCEAN TROPICAL WAVE PREVIOUSLY ALONG 41W WILL BE
RELOCATED A LITTLE FURTHER W TO 44W/45W ON THE 00Z SURFACE
ANALYSIS MAP. THIS ADJUSTMENT IS BASED ON ANIMATED SSMI
PRECIPITABLE WATER IMAGERY AND HOVMOLLER ANALYSIS...AS WELL AS
SATELLITE IMAGERY SHOWING A SURGE OF LOW LEVEL CLOUDINESS
ROUGHLY E OF 45W. THE WAVE IS MOVING WEST AT 15 KT. THIS REMAINS
A LOW AMPLITUDE WAVE WITH NO SIGNIFICANT CONVECTION OUTSIDE THE
ITCZ.

TROPICAL WAVE IS ALONG 57W SOUTH OF 15N MOVING WEST 10 TO 15 KT.
THIS IS A LOW AMPLITUDE WAVE WITH SCATTERED MODERATE CONVECTION
WITHIN 60 NM OF AXIS FROM 7N TO 9N.

AN CARIBBEAN SEA TROPICAL WAVE IS ALONG 70W SOUTH OF 17N MOVING
WEST 15 KT. THE WAVE IS DIFFICULT TO DETECT IN SATELLITE IMAGERY
AND PLACEMENT IS BASED ON CONTINUITY. NO SIGNIFICANT CONVECTION
IS NOTED WITH THIS WAVE.

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 87W SOUTH OF
19N...FROM WESTERN HONDURAS N TO JUST OFF THE BELIZE
COAST...MOVING WEST AT 10 TO 15 KT. NO SIGNIFICANT CONVECTION IS
ASSOCIATED WITH THIS WAVE. THIS IS DUE IN PART TO DRY SUBSIDENT
NLY FLOW ALOFT OVER THE WAVE POSITION...BETWEEN AN UPPER LEVEL
LOW CENTERED JUST TO E...AND AN UPPER LEVEL ANTICYCLONE TO THE W.

...THE ITCZ...
FROM 11N15W AT THE AFRICA COAST TO 7N22W 5N32W 4N41W TO 4N51W
NEAR THE BORDER OF FRENCH CAYENNE AND BRAZIL. SCATTERED MODERATE
CONVECTION WITHIN 90 NM N OF AXIS BETWEEN 18W AND 28W.

...DISCUSSION...
THE GULF OF MEXICO...
LARGE MID/UPPER SHORT WAVE TROUGH IS PUSHING THROUGH THE LOWER
MISSISSIPPI VALLEY. THIS WILL MOVE OVER THE NRN GULF OF MEXICO
TONIGHT. AN UPPER LEVEL ANTICYCLONE IS CENTERED OVER THE FLORIDA
PENINSULA...BLUNTING THE SWD APPROACH OF THE UPPER TROUGH AS IT
LIFTS OUT TO THE MID ATLC STATES. THE SWLY FLOW ALOFT BETWEEN
THE TWO FEATURES IS DRAWING DEEP LAYER MOISTURE FROM THE BAY OF
CAMPECHE THROUGH THE NE GULF. ISOLATED SHOWERS AND
THUNDERSTORMS ARE MOVING INTO THE NW GULF WATERS OFF TEXAS AND
LOUISIANA IN RESPONSE TO THE APPROACHING SHORT WAVE...BUT WILL
DIMINISH THROUGH TONIGHT AS THE TROUGH LIFTS OUT.
OTHERWISE...LIGHT TO MODERATE SLY FLOW IS NOTED AT THE SURFACE
ON THE WRN EDGE OF HIGH PRES CENTERED OVER THE WRN ATLC.

THE CARIBBEAN SEA...
AN UPPER LEVEL TROUGH IS ORIENTED E-W ACROSS THE CARIBBEAN BASIN
ALONG 17N...WITH MAIN CYCLONIC ROTATION CENTERED NEAR 17N85W AND
18N67W. SUBSIDENT DRY AIR ASSOCIATED WITH THIS TROUGH IS
SUPPRESSING CONVECTION AND GENERAL CLOUD DEVELOPMENT OVER THE
NRN CARIBBEAN N OF 16N. THE ONLY EXCEPTION IS MINOR CONVECTION
OVER PUERTO RICO AND HISPANIOLA...ENHANCED IN PART DUE TO SOME
DESTABILIZATION DELIVERED BY COLD CORE CENTER OF UPPER LOW.
FURTHER S...A BROAD UPPER ANTICYCLONE IS CENTERED OVER
VENEZUELA. UPPER LEVEL WLY SHEAR DOMINATES BETWEEN THE UPPER
TROUGH AND THE ANTICYCLONE ACROSS THE CARIBBEAN S OF 17N.
DIVERGENCE ALOFT ALONG WITH STRONG LOW LEVEL ELY CONVERGENCE IS
PROMOTING LARGE CLUSTER OF CONVECTION OVER THE SW
CARIBBEAN...FROM 10N TO 13N W OF 80W. SURFACE HIGH PRES N OF THE
AREA IS MAINTAINING MODERATE TO FRESH ELY FLOW AT THE SURFACE
ACROSS THE CENTRAL CARIBBEAN.

THE ATLANTIC OCEAN...
UPPER LEVEL TROUGH EXTENDS FROM CYCLONIC CIRCULATION ALOFT NEAR
20N41W...SW TO UPPER TROUGH OVER CARIBBEAN...N OF OF AN UPPER
ANTICYCLONE CENTERED OFF THE GUIANA COAST NEAR 12N48W. DRY MID
AND UPPER LEVELS DUE TO THE SUBSIDENCE ASSOCIATED WITH THE UPPER
TROUGH IS SUPPRESSING CONVECTION OVER THE WRN ATLC N OF 15N.
DIVERGENCE ALOFT ON THE W SIDE OF UPPER ANTICYCLONE IS ENHANCING
CONVECTION E OF TRINIDAD NEAR THE TROPICAL WAVE IN THE AREA.
HOWEVER NLY FLOW ALOFT ON THE E SIDE OF THE UPPER ANTICYCLONE IS
SUPPRESSING CONVECTION ACROSS THE CENTRAL TROP ATLC. FURTHER
E...A BROAD UPPER ANTICYCLONE IS CENTERED OVER THE CAPE VERDE
ISLAND AREA NEAR 17N21W. DIVERGENCE ALOFT ALONG THE PERIPHERY OF
THIS UPPER ANTICYCLONE IS ENHANCING CONVECTION ALONG THE ITCZ IN
THE SLIGHTLY MORE MOIST EASTERN TROP ATLC. MEANWHILE...FRESH ELY
FLOW PERSISTS S OF 20N ACROSS THE ATLC BETWEEN MID ATLC SURFACE
RIDGE TO THE N AND TROP WAVE PROGRESSION TO THE S.

$$
CHRISTENSEN


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