[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 282316
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU 28 OCT 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED ABOUT 420 NM E OF BARBADOS IS ALONG
52W/53W S OF 18N MOVING W 10-15 KT. A WELL-DEFINED LOWER LEVEL
ROTATION IS STILL APPARENT IN SATELLITE IMAGERY BUT DEEP
CONVECTION IS BEING SUPPRESSED BY MID/UPPER LEVEL SUBSIDENCE.
SCATTERED SHOWERS/TSTMS ARE FROM 13N-17N BETWEEN 51W-53W.

TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN AND COLOMBIA IS
ALONG 76W S OF 17N MOVING W 10-15 KT. THE WAVE IS BECOMING A
LITTLE BETTER DEFINED IN SATELLITE IMAGERY NOW THAT IT IS MOVING
AWAY FROM THE BROAD AREA OF LOW PRES OVER THE E CARIBBEAN. A
SMALL AREA OF SCATTERED MODERATE CONVECTION IS SE OF JAMAICA
FROM 15N-17N BETWEEN 74W-77W.

...ITCZ...

ITCZ AXIS IS ALONG 14N10W 7N30W 9N50W 10N70W 9N80W.  SCATTERED
MODERATE CONVECTION IS ALONG THE COAST OF W AFRICA FROM 8N-11N
BETWEEN 12W-16W.  ISOLATED MODERATE CONVECTION IS FROM 2N-8N
BETWEEN 19W-31W.  WIDELY SCATTERED MODERATE CONVECTION IS FROM
12N-15N BETWEEN 37W-40W.  SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION IS OVER N VENEZUELA AND N COLOMBIA FROM 9N-12N
BETWEEN 66W-76W.  SIMILAR CONVECTION IS INLAND OVER PANAMA AND
COSTA RICA.

...DISCUSSION...

GULF OF MEXICO...
THE GULF OF MEXICO IS UNDER DRY AND TRANQUIL CONDITIONS AS
STRONG DEEP LAYERED RIDGING REMAINS IN PLACE. THE RIDGE IS
ANCHORED BY A MID/UPPER LEVEL HIGH CENTERED OVER THE W GULF NEAR
22N90W WITH ASSOCIATED SUBSIDENCE COVERING THE ENTIRE GULF.
A WEAK MIDDLE TO UPPER LEVEL LOW IS MOVING NEWD ALONG THE
MEXICO/TEXAS COAST NEAR 26N97W BUT THIS FEATURE IS MOISTURE
STARVED AND UNABLE TO PRODUCE ANY SIGNIFICANT WEATHER. AT THE
SURFACE...RIDGE EXTENDS FROM THE E UNITED STATES SWD OVER
FLORIDA WITH COOL NE BREEZES CONTINUING OVER FLORIDA AND RETURN
FLOW OVER THE W GLFMEX INTO TEXAS.

CARIBBEAN...
SHARP MID/UPPER LEVEL TROUGH WHICH HAS BEEN POSITIONED OVER THE
CENTRAL CARIBBEAN DURING THE LAST FEW DAYS IS FINALLY WEAKENING
AS THE ATTENDANT UPPER JET LIFTS INTO THE ATLC. TROUGH AXIS
CURRENTLY EXTENDS FROM THE MONA PASSAGE TO NICARAGUA DELINEATING
SUBSIDENCE AND VERY DRY NE FLOW OVER THE W HALF OF THE CARIBBEAN
FROM MOIST SLY FLOW OVER THE E CARIBBEAN. THIS PATTERN CONTINUES
TO SUPPORT UNSTABLE/STORMY CONDITIONS OVER THE E CARIBBEAN WITH
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION CURRENTLY
OBSERVED FROM 9N-12N BETWEEN 66W-76W. ONLY PATCHY STRATOCUMULUS
CLOUDS AND ISOLATED SHOWERS ARE OBSERVED W OF THE UPPER TROUGH
AXIS.  LATEST WATER VAPOR IMAGERY INDICATES THAT THE UPPER
TROUGH IS BEGINNING TO FRACTURE AS THE ATLC PORTION BECOMES MORE
PROGRESSIVE. THIS EVOLUTION WILL ALLOW THE CARIBBEAN PORTION OF
THE TROUGH TO RETROGRADE DURING THE NEXT 2 DAYS WITH THE BEST
UPPER DYNAMICS/LIFT AND ASSOCIATED CLOUDS/CONVECTION GRADUALLY
SHIFTING MORE TOWARDS THE CENTRAL AND SW CARIBBEAN.

ATLANTIC WEST OF 50W...
SHARP MID/UPPER LEVEL TROUGH REMAINS OVER THE W ATLC EXTENDING
FROM 35N60W SWD TO HISPANIOLA.  DRY MID/UPPER LEVEL NW FLOW AND
MODERATE SUBSIDENCE BEHIND THE TROUGH IS PRODUCING FAIR WEATHER
UPSTREAM OF A DEVELOPING SURFACE COLD FRONT FROM 32N50W TO
HISPANIOLA. THE FRONT IS BEING REINFORCED BY IMPULSES ROTATING
ABOUT A STRONG AREA OF LOW SYSTEM N OF THE AREA OFF THE CANADIAN
MARITIMES.  FARTHER E... A 60-80 KT SUBTROPICAL JET FLANKS THE E
PORTION OF THE UPPER TROUGH AND IS PROVIDING SUPPORT FOR A
DEVELOPING AREA OF SCATTERED SHOWERS/THUNDERSTORMS OVER THE
CENTRAL ATLC. THIS ACTIVITY IS PRIMARILY FOCUSED WITHIN 2 DEG
EITHER SIDE OF A LOW-LEVEL CONVERGENCE LINE/TROF FROM THE
LEEWARD ISLANDS NEWD TO 30N48W. THIS ACTIVITY WILL LIKELY
INCREASE IN COVERAGE/INTENSITY AND LIFT NEWD DURING THE NEXT 2
DAYS AS THE UPPER TROUGH SHARPENS. A 1019 MB SURFACE HIGH IS
OVER THE E ATLANTIC NEAR 25N33W PRODUCING MOSTLY FAIR WEATHER
FROM 15N-30N BETWEEN 10W-45W.

ATLANTIC EAST OF 50W...
MOST OF THE E/CNTRL SUBTROPICAL ATLC IS DOMINATED BY STRONG
DEEP-LAYERED RIDGING ALIGNED E/W ALONG 25N. AN 80 KT SUBTROPICAL
JET EXTENDS AROUND THE N PERIPHERY OF THE RIDGE JUST N OF THE
AREA WITH ASSOCIATED MID/HIGH LEVEL CLOUDINESS SPREADING FROM W
TO E POLEWARD OF 28N.  S OF THE JET...A WEAK UPPER TROUGH/SHEAR
AXIS UNDERCUTS THE RIDGE PRODUCING CONFLUENT FLOW BETWEEN
15N-25N. A SURFACE TROUGH ORIGINATING FROM A MID-LATITUDE LOW
NEAR IRELAND EXTENDS SWD TO THE CANARY ISLANDS. HOWEVER...THE
BULK OF THE UPPER DYNAMICS ARE CONFINED WELL N OF THE AREA AND
THE TROUGH IS ESSENTIALLY DRY. FARTHER S IN THE TROPICS...A
NEARLY STATIONARY MID/UPPER LOW OVER THE CNTRL ATLC NEAR 17N42W
CONTINUES TO PRODUCE DIVERGENT FLOW AND ENHANCED ITCZ CONVECTION
E OF 40W WHILE MODERATE TO STRONG SUBSIDENCE SUPPRESSES ITCZ
ACTIVITY W OF 40W.

$$
FORMOSA














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