[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041805
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI AUG 04 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
1700 UTC.

...SPECIAL FEATURE...

CHRIS REMAINS POORLY ORGANIZED OVER THE SOUTHEAST BAHAMAS. THE
CENTER OF TROPICAL DEPRESSION CHRIS AT 04/1800 UTC IS NEAR 21.4N
72.2W...OR ABOUT 25 NM SOUTH OF PROVIDENCIALES...MOVING WEST
NEAR 11 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1012 MB.
THE MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH HIGHER GUSTS.
CHRIS IS EXPECTED TO PRODUCE TOTAL RAINFALL  AMOUNTS OF 1 TO 2
INCHES ACROSS THE DOMINICAN REPUBLIC...THE TURKS AND
CAICOS...THE SOUTHEAST BAHAMAS...HAITI AND EASTERN CUBA...WITH
ISOLATED TOTALS OF UP TO 4 INCHES OVER THE HIGHER TERRAIN
THROUGH TONIGHT. 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.
CHRIS REMAINS SQUEEZED BETWEEN TWO UPPER-LEVEL LOWS AND IT DOES
NOT APPEAR IN THE SHORT-TERM THAT THE SHEAR WILL RELAX.
HOWEVER...IT WOULD NOT TAKE MUCH FOR CHRIS TO RESTRENGTHEN BACK
TO TROPICAL STORM STATUS IF NEW CONVECTION DEVELOPS NEAR THE
CENTER. THE INTENSITY FORECAST KEEPS IN THIS POSSIBILITY.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 50W/51W S OF 17N
MOVING WEST 15 TO 20 KT. VISIBLE IMAGERY SHOWS SOME WEAK
CYCLONIC TURNING ABOUT THE WAVE AXIS BUT OVERALL THE EXACT
POSITION HAS BEEN DIFFICULT TO LOCATE THIS AFTERNOON...AS SHOWER
AND TSTM ACTIVITY IN THE VICINITY HAS REMAINED MINIMAL. THE 12Z
LOCATION WAS SOMEWHAT A CONSEQUENCE OF CONTINUITY FROM PREVIOUS
ANALYSES. THE UW-CIMMS SAHARAN LAYER ANALYSIS DEPICTS A FAIRLY
DENSE REGION OF DUST AFFECTING THE WAVE...BUT ALSO SHOWS MUCH
LESS CONCENTRATION TO THE EAST OF THE 12Z FIX FROM 10N TO 18N
BETWEEN 40W AND 50W. VISIBLE IMAGERY ANIMATIONS FROM TODAY ALSO
SUGGEST THE CORE/AXIS OF THIS WAVE MAY ACTUALLY BE CLOSER TO
46W/47W. THIS WAS NOT APPARENT AT 12Z...BUT NONETHELESS...THE
18Z POSITION MAY REFLECT THIS NEW POSITION ESTIMATE. GFS ALSO
INITIALIZES A LOW LEVEL VORTICITY MAXIMUM IN THIS VICINITY THAT
MOVES OVER THE LESSER ANTILLES BY 07/0000 UTC.

A WESTERN CARIBBEAN SEA TROPICAL WAVE EXTENDING MAINLY THROUGH
NICARAGUA...HONDURAS...AND THE EAST PACIFIC IS ALONG 86W SOUTH
OF 16N MOVING WEST 15 KT. A CLUSTER OF MODERATE CONVECTION LIES
IN THE NW CARIBBEAN FROM 16N TO 21N BETWEEN 83W AND 89W...BUT
THIS MAY BE MORE ASSOCIATED WITH UPPER DIFFLUENCE BETWEEN THE
UPPER LOW OVER CENTRAL FLORIDA AND THE UPPER HIGH OVER CENTRAL
MEXICO.

...THE ITCZ...
ITCZ 11N15W 8N49W 7N52W AND INLAND THROUGH SOUTH AMERICA TO NEAR
7N77W. NUMEROUS MODERATE CONVECTION IS LOCATED JUST OFF THE WEST
AFRICAN COAST...MAINLY SOUTH OF THE ITCZ AXIS...FROM 5N TO 11N
BETWEEN 13W AND 21W. THIS ACTIVITY IS LIKELY BEING ENHANCED BY A
DEVELOPING TROPICAL WAVE. FROM 5N TO 13N BETWEEN 22W AND 30W
LIES SCATTERED MODERATE CONVECTION...WITH MOSTLY ISOLATED
SHOWERS AND THUNDERSTORMS TO THE WEST OF THIS AREA THROUGH THE
SOUTH AMERICAN COAST.

...DISCUSSION...
THE GULF OF MEXICO...
A CLUSTER OF MODERATE CONVECTION IS LOCATED IN THE WESTERN BAY
OF CAMPECHE FROM 18N TO 23N BETWEEN 92W AND 98W. THIS IS
ASSOCIATED WITH UPPER LEVEL DIFFLUENCE BETWEEN AN ANTICYCLONE
OVER CENTRAL MEXICO AND THE UPPER LOW OVER CENTRAL FLORIDA.
BROAD UPPER NORTHERLY FLOW BETWEEN THESE FEATURES IS DOMINATING
MUCH OF THE GULF THIS AFTERNOON. SCATTERED SHOWERS AND
THUNDERSTORMS WITH EMBEDDED MODERATE CONVECTION DOTS MUCH OF THE
GULF WATERS BETWEEN SOUTH FLORIDA AND NE MEXICO THIS AFTERNOON.
THIS ACTIVITY HAS OCCURRED NEAR THE UPPER TROUGH AXIS THAT IS
EXTENDING WEST FROM CENTRAL FLORIDA. SATELLITE AND RADAR DATA
ALSO SHOW A LINE OF SHOWERS AND THUNDERSTORMS PUSHING SOUTH INTO
THE NORTHERN GULF FROM PANAMA CITY THROUGH ST. GEORGE ISLAND.
THE SURFACE PATTERN REMAINS FAIRLY BENIGN THIS AFTERNOON WITH
WINDS GENERALLY BELOW 15 KT AND SEAS BELOW 4 FT...WITH THE
WESTERN PORTION OF THE ATLANTIC HIGH DOMINATING. TROPICAL
DEPRESSION CHRIS WELL E OF AREA IS FORECAST TO MOVE W JUST N OF
CUBA AND STRENGTHEN TO A TROPICAL STORM LATE TONIGHT AND ENTER
STRAITS OF FLORIDA LATE SAT NIGHT AND CROSS ERN GULF SUN AND SUN
NIGHT AND MOVE CROSS CENTRAL GULF MON. CHRIS EXPECTED TO REACH
WRN GULF LATE MON NIGHT AND TUE.

THE CARIBBEAN SEA...
TROPICAL DEPRESSION CHRIS IS MOVING THROUGH THE TURKS AND
CAICOS/SE BAHAMAS. A CLUSTER OF MODERATE CONVECTION SE OF THE
CENTER OF T.D. CHRIS IS EXPERIENCING NORTHERLY SHEAR IN THE
NORTH CENTRAL CARIBBEAN JUST SOUTH OF THE DOMINICAN REPUBLIC.
THE OTHER AREA OF ACTIVE WEATHER IN THE CARIBBEAN LIES IN THE NW
PORTION WHERE SCATTERED MODERATE CONVECTION IS NOTED FROM 16N TO
22N BETWEEN 83W AND 88W...LIKELY ASSOCIATED WITH UPPER
DIFFLUENCE THE UPPER LOW OVER CENTRAL FLORIDA AND A UPPER HIGH
OVER CENTRAL MEXICO. ASIDE FROM THESE MODERATE SHOWERS AND
THUNDERSTORMS MUCH OF THE REMAINDER OF THE CARIBBEAN BETWEEN 61W
AND 80W IS DOMINATED BY UPPER NORTHERLIES AND DRY AIR/FAIR
WEATHER. 10-20 KT EASTERLY TRADES DOMINATE MUCH OF THE CARIBBEAN
THIS AFTERNOON ON THE SW PORTION OF THE ATLANTIC HIGH. THIS IS
EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS...WITH THE
STRONGEST WINDS GENERALLY EXPECTED IN THE AREA BETWEEN THE
COLOMBIA/VENEZUELA COAST AND HISPANIOLA THROUGH JAMAICA...AS THE
HIGH INTERACTS WITH THE COLOMBIAN LOW.

THE ATLANTIC OCEAN...
A PERSISTENT LARGE UPPER LEVEL LOW CONTINUES TO DRIFT TO THE WNW
CURRENTLY CENTERED OVER CENTRAL FLORIDA. THIS LOW IS HELPING TO
DESTABILIZE THE ATMOSPHERE GENERATING SCATTERED SHOWERS AND
TSTMS OVER S FLORIDA EXTENDING WWD INTO THE GULF AND SWWD INTO
THE NW CARIBBEAN. ANOTHER LARGE UPPER LEVEL LOW IS LOCATED TO
THE NE OF PUERTO RICO NEAR 22N64W. THIS IS THE UPPER LOW THAT IS
PROVIDING NNELY SHEAR OVER T.D. CHRIS'S CIRCULATION. A NARROW
AREA OF LOWER SHEAR IS BETWEEN THESE UPPER LOWS THAT MAY SUPPORT
A SLIGHTLY MORE FAVORABLE ENVIRONMENT FOR THE DEPRESSION.  A
THIRD LARGE UPPER LEVEL LOW IS CENTERED JUST TO THE N OF THE
DISCUSSION AREA IN THE E ATLC CENTERED NEAR 35N37W WITH ITS
CYCLONIC CIRCULATION COVERING THE AREA N OF 24N BETWEEN 25W-42W.
THE REMAINDER OF THE ATLC IS DOMINATED BY A LARGE-SCALE UPPER
RIDGE WITH A HIGH CENTER NEAR 19N41W. PLENTY OF DRY/STABLE AIR
IS UNDER THE INFLUENCE OF THE UPPER RIDGING OUT TO 55W BETWEEN
13N-24N. UPPER DIFFLUENCE BETWEEN THIS LARGE RIDGE AND THE UPPER
LOW NEAR 35N37W IS PRODUCING A SWATH OF SCATTERED SHOWERS FROM
27N-37N BETWEEN 33W-46W. AT THE SURFACE...BESIDES FOR THE
TROPICAL DEPRESSION AND WAVE...WEAK SFC RIDGING IS THE THEME
EXTENDING FROM THE AZORES TO A 1020 MB HIGH NEAR 27N58W
STRETCHING ACROSS THE GULF.

$$
WILLIS/CANGIALOSI







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