[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 021807
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED AUG 02 2006

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1735 UTC.

...SPECIAL FEATURE...

TROPICAL STORM CHRIS CONTINUES TO SKIRT THE NORTHERNMOST LEEWARD
ISLANDS. THE CENTER OF T.S. CHRIS IS LOCATED NEAR 19.5 NORTH
64.0 WEST OR ABOUT 85 NM...EAST-NORTHEAST OF ST. THOMAS AT
02/1500 UTC. CHRIS IS MOVING TOWARD THE WEST-NORTHWEST NEAR 9
KT. ON THIS TRACK...THE CENTER OF CHRIS WILL REMAIN NORTH OF THE
VIRGIN ISLANDS AND PUERTO RICO THIS AFTERNOON AND EVENING.
HOWEVER...SOME OF THE STRONG RAIN BANDS ON THE SOUTH SIDE OF
CHRIS MAY AFFECT PUERTO RICO AND THE VIRGIN ISLANDS LATER
TONIGHT AND EARLY THURSDAY MORNING. THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1007 MB. THE MAXIMUM SUSTAINED WINDS REMAIN
55 KT WITH HIGHER GUSTS. CHRIS IS EXPECTED TO PRODUCE TOTAL
RAINFALL ACCUMULATIONS OF 2 TO 4 INCHES OVER THE NORTHERN
LEEWARD ISLANDS...THE U.S. VIRGIN ISLANDS...AND PORTIONS OF
PUERTO RICO...WITH ISOLATED MAXIMUM AMOUNTS OF 8 INCHES POSSIBLE
OVER HIGHER TERRAIN THROUGH THURSDAY. PLEASE REFER TO THE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/ WTNT23
KNHC AND THE PUBLIC ADVISORY MIATCPAT3/WTNT33 KNHC FOR MORE
DETAILS. RECENT AIRCRAFT DATA FOUND THAT CHRIS HAS NOT
STRENGTHENED YET. MODERATE CONVECTION/HEAVY SHOWERS AND TSTMS
ASSOCIATED WITH CHRIS ARE NOTED FROM 19N TO 22N BETWEEN 61W AND
66W. UW-CIMMS SHEAR ANALYSIS STILL SHOWS ABOUT 10KTS OF SHEAR
OVER CHRIS...AND THE CYCLONE IS EXPECTED TO MOVE WEST INTO AN
UPPER COL REGION DURING THE NEXT FEW DAYS WHICH IS A REASONABLY
FAVORABLE ENVIRONMENT FOR STRENGTHENING.

...TROPICAL WAVES...

A TROPICAL WAVE IN THE EASTERN ATLANTIC ALONG 36W/37W S OF 18N
MOVING WEST 15-20 KT. THIS WAVE REMAINS SUPERIMPOSED UPON A
QUASI STATIONARY MONSOONAL TROUGH WITH SURFACE SW FLOW NOTED
BACK TO THE NE COAST OF BRAZIL ON THE SOUTH SIDE OF THE ITCZ.
BROAD CYCLONIC CURVATURE WITH A VAGUE INVERTED V PATTERN
ASSOCIATED WITH THIS WAVE IS STILL NOTED IN VISIBLE IMAGERY THIS
AFTERNOON. WIDELY SCATTERED SHOWERS AND TSTMS EXISTS NORTH OF
THE ITCZ FROM 10N TO 15N BETWEEN 31W AND 43W...WITH A PATCH OF
MODERATE CONVECTION JUST EAST OF THE AXIS NEAR 14N34W.
WIDESPREAD SHOWERS AND TSTMS EXIST JUST SOUTH OF THE
ITCZ/MONSOON TROUGH FROM 5N TO 10N BETWEEN 31W AND 44W.

THE TROPICAL WAVE THAT WAS MOVING THROUGH THE SE CARIBBEAN SEA
AND VENEZUELA YESTERDAY WAS RECENTLY REMOVED FROM THE ANALYSIS
DUE TO A LACK OF CLEAR EVIDENCE. TODAYS SATELLITE AND
SURFACE OBSERVATIONS SUGGEST THE WAVE HAS REEMERGED...AND IS
THUS REPLACED ON THE 12Z MAP ALONG 71W/72W S OF 13N. ANALYSIS OF
THE HOVMOLLER DIAGRAMS ON THE TAFB WEBSITE SHOW THAT THE REGION
HAD VERY LITTLE CONVECTIVE ACTIVITY YESTERDAY...BUT REDEVELOPED
LAST NIGHT AND THIS MORNING. A CLUSTER OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS LOCATED IN THE SW
CARIBBEAN THAT EXTENDS S THROUGH PANAMA AND INTO THE GULF OF
PANAMA...SOME OF THIS MAY BE ASSOCIATED WITH THE WAVE BUT IS
ALSO LIKELY BEING ENHANCED BY THE ITCZ AND THE COLOMBIAN LOW. A
SMALLER CLUSTER OF MODERATE CONVECTION IS NOTED EAST OF THE AXIS
NOW MOVING THROUGH NW VENEZUELA.

A TROPICAL WAVE IS MOVING THROUGH THE BAY OF CAMPECHE AND
SOUTHERN MEXICO ALONG 95W S OF 22N MOVING W NEAR 15 KT. WEAK
CURVATURE ASSOCIATED WITH THIS WAVE IS MAINLY NOTED IN THE EAST
PACIFIC WATERS TO THE SOUTH. GFS INITIALIZED A WEAK REGION OF
700 MB POSITIVE VORTICITY ADVECTION IN THE SOUTHERN BAY OF
CAMPECHE..WHICH IS VERY CLOSE TO WHERE THE PATCH OF MODERATE
CONVECTION DEVELOPED THIS MORNING NEAR 19N95W. THIS HAS BEEN
DIMINISHING IN BOTH STRENGTH AND COVERAGE OVER THE PAST FEW
HOURS THOUGH. ANOTHER PATCH OF MODERATE CONVECTION IS NOTED
BETWEEN COASTAL VERACRUZ AND TAMPICO MEXICO...WHICH SEEMS TO BE
MORE ASSOCIATED WITH UPPER DIFFLUENCE ALONG WITH UPSLOPE FLOW.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N16W 10N35W 9N40W TO THE SOUTH
AMERICAN COAST NEAR 6N53W.  A PATCH OF MODERATE CONVECTION LIES
EAST OF THE WEST AFRICAN COAST/SOUTH OF THE ITCZ AXIS FROM 6N TO
7N BETWEEN 16W AND 19W. ISOLATED SPOTS OF MODERATE TO STRONG
CONVECTION HAVE DEVELOPED ALONG OR JUST WEST OF THE AFRICAN
COAST FROM 7N TO 14N MAINLY AFTER 1500 UTC. THIS CONVECTION MAY
BE IN ASSOCIATION WITH A DEVELOPING TROPICAL WAVE...WITH THE
DAKAR SOUNDING SHOWING SIGNS OF THIS AS WELL WITH LOW LEVEL
NORTHERLY FLOW. SCATTERED SHOWERS AND TSTMS ARE FOUND SOUTH OF
THE ITCZ WITHIN THE SOUTHWESTERLY MONSOONAL FLOW IN A BOX FROM
4N TO 11N BETWEEN 20W AND 48W. A CLUSTER OF MODERATE CONVECTION
IS ALSO NOTED IN THE EXTREME SW CARIBBEAN SEA JUST NORTH OF THE
PANAMA COAST.

...DISCUSSION...
THE GULF OF MEXICO...
UPPER LEVEL E/SE FLOW AND DRY AIR/FAIR WEATHER DOMINATES MUCH OF
THE EAST AND CENTRAL GULF OF MEXICO ON THE SOUTH SIDE OF AN
UPPER HIGH CENTERED NEAR KNOXVILLE TENNESSEE. AN UPPER LEVEL LOW
IS SEEN SPINNING ON WATER VAPOR OVER ERN MEXICO AND SRN TEXAS.
DIFFLUENCE BETWEEN THIS FEATURE AND UPPER RIDGING TO ITS
SOUTH...ALONG WITH SOME LOW LEVEL UPSLOPE FLOW...IS GENERATING A
PATCH OF MODERATE CONVECTION IN THE SW GULF BETWEEN COASTAL
VERACRUZ AND TAMPICO MEXICO. ISOLATED SHOWERS AND THUNDERSTORMS
ARE NOTED ELSEWHERE IN THE WESTERN THIRD OF THE GULF. SFC WINDS
ACROSS THE GULF REMAIN FAIRLY LIGHT...5 TO 15KT FROM THE E/SE ON
THE S/SW PORTION OF SFC HIGH PRESSURE. SIMILAR SFC CONDITIONS
EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS.

THE CARIBBEAN SEA...
THE MAIN FEATURE IN THE REGION IS TROPICAL STORM CHRIS WHICH IS
AFFECTING THE NRN LEEWARD ISLANDS. GUSTY WINDS AND SCATTERED
MODERATE CONVECTION IS N OF 17N BETWEEN 61W-66W. FOR MORE
DETAILS...REFER TO THE SPECIAL FEATURE SECTION ABOVE. A CLUSTER
OF MODERATE CONVECTION NEAR THE ITCZ IS MOVING W THROUGH THE SW
CARIBBEAN AS DESCRIBED ABOVE. THE OTHER AREA OF UNSETTLED
WEATHER IN THE CARIBBEAN IS SCATTERED MODERATE CONVECTION FROM
17N TO 23N BETWEEN 78W AND 85W...MAINLY ASSOCIATED WITH UPPER
DIFFLUENT FLOW BETWEEN UPPER RIDGING EXTENDING EAST THROUGH THE
YUCATAN AND NW CARIBBEAN A WELL-DEFINED UPPER LOW NEAR THE
BAHAMAS. THE REMAINDER OF THE CARIBBEAN HAS A DRY/STABLE UPPER
LEVEL ENVIRONMENT WITH WEAK UPPER RIDGING DOMINATING. AT THE
SURFACE...10 TO 25 KT E TO SE TRADE WINDS ARE DOMINATING ON THE
SW SIDE OF THE ATLANTIC HIGH...WITH THE STRONGEST WINDS IN THE
CENTRAL CARIBBEAN BETWEEN 70W AND 80W.

THE ATLANTIC OCEAN...
THE PERSISTENT UPPER LOW THAT HAS BEEN SPINNING E OF THE BAHAMAS
THE LAST SEVERAL DAYS HAS SHIFTED SLOWLY WESTWARD TODAY AND IS
NOW CENTERED JUST NORTH OF ELEUTHERA. LARGE SCALE UPPER RIDGING
DOMINATES THE W ATLC WATERS NORTH OF THIS LOW. TO THE
EAST...DISTINCT OUTFLOW IS NOTED ABOVE T.S. CHRIS. AN UPPER TROF
LIES NE OF CHRIS WITH THE PORTION OF ITS AXIS S OF 30N BETWEEN
25N62W AND 30N52W. AN UPPER ANTICYCLONE CENTERED NEAR 20N34W IS
AFFECTING MUCH OF THE TROPICAL ATLANTIC WATERS BETWEEN 47W AND
THE AFRICAN COAST. 02/12Z UW-CIMSS SAHARAN LAYER ANALYSIS SHOWS
THE LEADING EDGE OF DENSE DUST STRETCHING OUT TO 40W MAINLY N OF
15N. AT THE SURFACE...HIGH PRESSURE IS DOMINATING MUCH OF THE
TROPICAL ATLANTIC WATERS ON THE SOUTH AND WEST PORTION OF ITS
1031 MB HIGH OVER THE AZORES AND A 1022 MB HIGH IN THE CENTRAL
ATLC NEAR 27N62W. THE OTHER SURFACE FEATURES NOTED ARE T.S CHRIS
AFFECTING THE NRN LEEWARD ISLANDS AND THE BROAD TROPICAL WAVE
ALONG 36W...SEE MORE INFO ON THESE FEATURES ABOVE.

$$
WILLIS


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