[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181100
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI AUG 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...TROPICAL WAVES...
AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 35W/36W SOUTH OF 21N
MOVING WEST NEAR 10 KT.  CYCLONIC TURNING OF LOW LEVEL CLOUDS IS
NOTED N OF THE ITCZ.  THE ONLY CONVECTION NEAR THIS WAVE IS
SCATTERED MODERATE...IN THE VICINITY OF THE ITCZ...FROM 10N-13N
BETWEEN 34W-39W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 51W/52W SOUTH OF 20N
MOVING WEST NEAR 15 KT.  AN INVERTED-V LOW LEVEL CLOUD SIGNATURE
IS NOTED IN LAST NIGHTS SHORTWAVE IR IMAGERY AND FIRST COUPLE
FRAMES OF THIS MORNINGS VISIBLE. SCATTERED SHOWERS AND TSTMS LIE
NEAR THE NRN PORTION OF THE WAVE AXIS FROM 18N-23N BETWEEN
51W-56W...AS THE WAVE INTERACTS WITH THE UPPER LOW NEAR 23N63W.
THE ONLY OTHER REGION OF CONVECTION NEAR THE WAVE IS CONFINED TO
THE ITCZ WITH ISOLATED MODERATE CONVECTION FROM 6N-12N BETWEEN
45W-55W.

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 85W SOUTH OF 22N
MOVING WEST 10 TO 15 KT. VERY LITTLE CYCLONIC CURVATURE IS NOTED
IN THE LOW CLOUD MOTIONS AND SURFACE OBSERVATIONS NEAR THIS WAVE
AXIS...AND THE WAVE MAY NEED TO BE REPOSITIONED FURTHER WEST
THROUGH THE EPAC ON THE 1200 UTC MAP DUE TO THE CYCLONIC SWIRL
AND CONVECTION NOTED NEAR 10N90W. AT THE PRESENT
LOCATION...ISOLATED SHOWERS AND TSTMS LIE WITHIN 150NM OF EITHER
SIDE OF THE AXIS S OF 18N. THE CLUSTER OF MODERATE TO STRONG
CONVECTION OFF THE CARIBBEAN COAST OF PANAMA AND COSTA RICA
SEEMS MORE ASSOCIATED WITH THE ITCZ.

...THE ITCZ...
ITCZ IS CENTERED ALONG 9N14W 10N34W 11N37W 10N50W 9N54W TO
INLAND OVER SOUTH AMERICA NEAR 8N72W. A MODERATE TO STRONG
CLUSTER OF CONVECTION LIES JUST NORTH OF THE AXIS...OFF THE
COAST OF AFRICA FROM 8N-12N BETWEEN 15W-17W. JUST TO THE SW OF
THIS CLUSTER LIES ANOTHER CLUSTER OF SCATTERED MODERATE
CONVECTION FROM 4N-8N BETWEEN 17W-21W. THERE ALSO APPEARS TO BE
SOME BROAD CYCLONIC TURNING IN THIS REGION. THIS ALONG WITH
ANALYSIS OF THE HOVMOLLER DIAGRAMS ON THE TAFB WEBSITE SUGGEST A
DEVELOPING TROPICAL WAVE MAY BE MOVING OFF OF AFRICA. A SMALL
CLUSTER OF MODERATE CONVECTION IS NOTED NEAR 7N27W. WIDELY
SCATTERED MODERATE CONVECTION LIE WITHIN 200NM OF THE AXIS
BETWEEN 34W-50W. A CLUSTER OF MODERATE CONVECTION IS ALSO SEEN
MOVING N FROM THE NE VENEZUELAN COAST.

...DISCUSSION...
THE GULF OF MEXICO...
THE MAIN FEATURE IN THE GULF IS A MID TO UPPER LEVEL LOW MOVING
INTO THE WRN PORTION...CENTERED NEAR 24N93W. THERE IS A
REFLECTION OF THIS AT THE SURFACE WITH CYCLONIC TURNING NOTED ON
NEARBY BUOY OBSERVATIONS...THOUGH AN EARLIER QUIKSCAT PASS
SUGGESTED THERE WAS NOT A CLOSED LOW AND THUS THE LOW HAS BEEN
REMOVED AND NOW A TROUGH IS PLACED ON THE MAP EXTENDING NE FROM
21N95W TO 28N89W. ISOLATED SHOWERS AND TSTMS ASSOCIATED WITH
THIS FEATURE DOT THE WRN GULF FROM 23N-28N BETWEEN 90W-98W.
WIDELY SCATTERED MODERATE CONVECTION ARE ALSO NOTED IN THE ERN
GULF S OF 28N PUSHING SW AROUND THE SE PORTION OF AN UPPER
ANTICYCLONE NEAR MEMPHIS TENNESSEE. LOOK FOR THESE SHOWERS AND
TSTMS TO GRADUALLY SPREAD W THROUGH THE GULF OVER THE NEXT
24HRS.

THE CARIBBEAN SEA...
THE MOST SIGNIFICANT WEATHER IN THE CARIBBEAN IS A CLUSTER OF
MODERATE TO STRONG CONVECTION IN THE SRN CARIBBEAN OFF THE COAST
OF PANAMA/COLOMBIA. CLOUD TOPS ASSOCIATED WITH THE CLUSTER OF
SCATTERED MODERATE CONVECTION BETWEEN JAMAICA AND CENTRAL CUBA
HAVE BEEN WARMING OVER THE LAST FEW HOURS...THOUGH NEW/SMALLER
CELLS HAVE DEVELOPED NEAR 21N79W AND NEAR 19N75W. THIS ACTIVITY
SEEMS TO BE COLOCATED WITH A DISTINCT AREA OF UPPER DIFFLUENCE
AND A LINGERING UPPER LOW JUST TO THE S OF WRN CUBA. MID TO
UPPER LEVEL W/WSW FLOW IS DOMINATING THE CENTRAL AND ERN
CARIBBEAN TONIGHT...FEEDING INTO THE LARGE UPPER LOW NE OF THE
LEEWARD ISLANDS. THIS IS BLOWING OFF THE TOPS OF THE CONVECTION
ALONG THE ITCZ OVER SOUTH AMERICA...WITH SOME SCATTERED SHOWERS
AND TSTMS SPILLING OVER INTO THE SRN CARIBBEAN FROM 11N-15N
BETWEEN 61W-75W. AT THE SURFACE...THE SW PORTION OF THE ATLC
HIGH IS INTERACTING WITH THE COLOMBIAN LOW...PRODUCING 15-20 KT
TRADES OVER MUCH OF THE CARIBBEAN.

THE ATLANTIC OCEAN...
THE PERSISTENT SURFACE LOW PRESSURE AREA OFF THE SOUTHEAST COAST
OF THE UNITED STATES IS NOW CENTERED ABOUT 85NM ENE OF
JACKSONVILLE. SATELLITE AND RADAR DATA INDICATE THAT THE
ASSOCIATED SHOWER ACTIVITY IS POORLY ORGANIZED...AND UPPER LEVEL
WINDS ARE NOT FAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT.
UW-CIMMS SHEAR ANALYSIS DEPICTS ABOUT 30 KTS OF NORTHERLY SHEAR
CURRENTLY OVER THIS REGION. SHOWERS AND THUNDERSTORMS WITH BRIEF
GUSTY WINDS COULD STILL AFFECT COASTAL AREAS OF GEORGIA AND
NORTHEASTERN FLORIDA DURING THE NEXT DAY OR SO AS THE SYSTEM
MOVES SLOWLY SOUTHWESTWARD. WIDELY SCATTERED MODERATE CONVECTION
IS SEEN ENE OF THE BAHAMAS FROM 24N-30N BETWEEN 67W-74W. THIS
APPEARS TO BE ASSOCIATED WITH UPPER DIFFLUENCE ALONG WITH
PERHAPS SOME WEAK SURFACE TROUGHING. JUST TO THE E OF THIS AREA
LIES SCATTERED SHOWERS AND TSTMS FROM 20N-30N BETWEEN 53W-65W.
THERE IS A WELL DEFINED UPPER LOW IN THIS VICINITY...WITH THE
CENTER NEAR 23N63W. MUCH OF THE CENTRAL AND ERN ATLC FROM
15N-30N BETWEEN THE COAST OF AFRICA AND 55W IS DOMINATED BY A
PAIR OF UPPER HIGHS...FAIR WEATHER...AND WEAK SURFACE HIGH
PRESSURE. BETWEEN THE UPPER HIGHS...THERE IS A NARROW UPPER
TROUGH AXIS EXTENDING N/S ALONG 39W. THERE IS A WEAK REFLECTION
OF THIS TO THE SURFACE AS VERIFIED BY AN EARLIER QUIKSCAT PASS
AND LOW CLOUD MOTIONS...THOUGH SHOWER AND TSTM ACTIVITY
ASSOCIATED WITH THIS FEATURE IS MINIMAL S OF 32N.

$$
WILLIS


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