[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291732
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI 29 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1645 UTC.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED ABOUT 200 NM E OF BARBADOS ALONG 56W S OF
18N MOVING W NEAR 15 KT. A DISTINCT LOW-LEVEL CIRCULATION IS
OBSERVED IN SATELLITE IMAGERY NEAR 16N BUT MODERATE/STRONG
SUBSIDENCE CONTINUES TO LIMIT DEEP CONVECTION. SCATTERED SHOWERS
AND THUNDERSTORMS ARE OBSERVED WITHIN 240 NM E OF AXIS.

TROPICAL WAVE LOCATED OVER THE W CARIBBEAN NEAR JAMAICA ALONG
78W S OF 19N MOVING W NEAR 10 KT. THE WAVE LIES ALONG THE
LEADING EDGE OF AN EASTERLY WIND SURGE WHICH EXTENDS ACROSS THE
E/CNTRL CARIBBEAN TO 65W.  ADDITIONALLY...THE WAVE IS LOCATED
JUST E OF A MID TO UPPER LEVEL TROUGH. THE COMBINATION OF UPPER
LEVEL DIVERGENCE AND LOW-LEVEL SPEED CONVERGENCE IS PRODUCING A
PERSISTENT AREA OF DEEP CONVECTION E OF THE WAVE AXIS WITH
SCATTERED MODERATE ACTIVITY FROM 12N-17N BETWEEN 73W-78W. THIS
ACTIVITY SHOWS NO SIGNS OF ORGANIZATION.

...ITCZ...

ITCZ AXIS IS ALONG 14N10W 11N20W 6N40W 12N55W 10N65W 11N80W.
SCATTERED MODERATE CONVECTION FROM 6N-9N BETWEEN 23W-27W AND
FROM 7N-9N BETWEEN 37W-42W.

...DISCUSSION...

GULF OF MEXICO...
DEEP-LAYERED RIDGING REMAINS OVER FLORIDA AND THE GULF OF MEXICO
PRODUCING YET ANOTHER DAY OF DRY/STABLE CONDITIONS. PATCHY
STRATOCUMULUS CLOUDS AND ISOLATED LOW TOPPED SHOWERS IS THE ONLY
WEATHER OF NOTE. SFC RIDGE EXTENDS SWD FROM THE E UNITED STATES
OVER THE CENTRAL GULF OF MEXICO TO THE COAST OF MEXICO NEAR
VERACRUZ. COOL NE FLOW CONTINUES OVER FLORIDA WITH SE RETURN
FLOW OVER THE W GLFMEX INTO TEXAS. THE MIDDLE TO UPPER LEVEL
RIDGE IS EXPECTED TO MOVE SLOWLY EWD AND FLATTEN OVER THE
WEEKEND KEEPING UPSTREAM DISTURBANCES N OF THE AREA.  THIS
PATTERN SHOULD MAINTAIN A DRY/TRANQUIL PATTERN THROUGH SUNDAY.

CARIBBEAN...
THE LARGE MID/UPPER LEVEL TROF WHICH PERSISTED OVER THE
CARIBBEAN SEA FOR MUCH OF THE WEEK CONTINUES TO SPLIT AS THE
MAIN ENERGY LIFTS NEWD OVER THE CENTRAL ATLC.  THE FRACTURED
TROUGH AXIS NOW EXTENDS FROM COSTA RICA NEWD OVER JAMAICA AND
HISPANIOLA. DIVERGENT UPPER LEVEL FLOW E OF THE TROUGH IS
ENHANCING CONVECTION NEAR THE TROPICAL WAVE ALONG 78W. ELSEWHERE
EAST OF THE UPPER TROUGH...MOIST SLY FLOW CONTINUES TO PRODUCE
AN UNSTABLE ENVIRONMENT WITH WIDELY SCATTERED
SHOWERS/THUNDERSTORMS E OF 70W.  CONFLUENT MID TO UPPER LEVEL
FLOW AND STRONG SUBSIDENCE WEST OF THE UPPER TROUGH IS PRODUCING
DRY/STABLE CONDITIONS OVER MUCH OF THE NW CARIBBEAN AND CENTRAL
AMERICA N OF COSTA RICA. THE FRACTURED UPPER TROUGH IS EXPECTED
TO DRIFT SLOWLY WESTWARD AND WEAKEN DURING THE WEEKEND.  THIS
PATTERN WILL FAVOR CONVECTION NEAR THE WESTWARD MOVING TROPICAL
WAVE WITH MORE SCATTERED ACTIVITY OVER THE CENTRAL AND E
CARIBBEAN.

ATLANTIC WEST OF 50W...
LARGE MID/UPPER LEVEL TROUGH LIES OVER THE W ATLC FROM PUERTO
RICO NEWD TO BEYOND 32N55W. ATTENDANT COLD FRONT ENTERS THE AREA
ALONG 32N45W SWD TO 25N55W WHERE IT BECOMES STATIONARY TO THE
U.S. VIRGIN ISLANDS.  MODERATE SUBSIDENCE AND DRY MIDDLE TO
UPPER LEVEL AIR WEST OF THE FRONT IS PRODUCING STABLE CONDITIONS
AND PATCHY STRATOCUMULUS CLOUDS TO THE U.S. EAST COAST.  EAST OF
THE FRONT...GOOD UPPER LEVEL DYNAMICS IS PRODUCING SCATTERED
MODERATE CONVECTION WITHIN 150 NM AHEAD OF THE FRONT.  THIS
ACTIVITY IS MOST NUMEROUS N OF 21N IN LINE WITH A 60-90 KT
SUBTROPICAL JET ON THE E SIDE OF THE UPPER TROF. THE UPPER JET
IS EXPECTED TO LIFT NEWD DURING THE WEEKEND WITH MOST OF THE
ACTIVITY SPREADING N OF 25N BY SUN.  MEANWHILE...DRY NW FLOW
WILL CONTINUE FOR MUCH OF THE W ATLC AS A SHORTWAVE TROUGH
CURRENTLY NEAR 65W DRAGS DOWN A REINFORCING SHOT OF COOL/DRY
AIR.

ATLANTIC EAST OF 50W...
BROAD MID/UPPER LEVEL RIDGING COVERS MUCH OF THE E/CNTRL ATLC
WITH AXIS ALIGNED NORTH/SOUTH ALONG 35W. AFOREMENTIONED
SUBTROPICAL JET AND MIDDLE TO UPPER LEVEL MOISTURE OVER THE
CENTRAL ATLC RIDES UP AND OVER THE RIDGE LEAVING THE AREA E OF
40W UNDER SUBSIDENCE AND DRY MIDDLE TO UPPER LEVEL AIR. TWO
DISTINCT UPPER LEVEL CUT-OFF LOWS ARE TRAPPED BENEATH THE RIDGE
NEAR 18N42W AND 24N32W. HOWEVER...GIVEN THE ABSENCE OF
MOISTURE...NEITHER FEATURE IS PRODUCING SIGNIFICANT WEATHER. AT
THE SURFACE...1020 MB HIGH IS CENTERED NEAR 25N35 WITH RIDGE
AXIS EXTENDING WSW TO 22N55W AND ENE TO AFRICA NEAR W SAHARA.
STRONG PRESSURE GRADIENT BETWEEN RIDGE AND CENTRAL ATLC COLD
FRONT IS PRODUCING MODERATE SLY FLOW.  OVER THE TROPICAL
ATLC...A WEAK MID/UPPER RIDGE IS LOCATED ABOUT 300 NM W OF THE
CAPE VERDE ISLANDS. HOWEVER...CYCLONIC FLOW ASSOCIATED WITH AN
UPPER LOW NEAR 18N42W PENETRATES WELL INTO THE TROPICAL BELT
RESTRICTING DEEP ELY FLOW TO S OF 10N E OF 30W.  ELSEWHERE...
MODERATE SUBSIDENCE W OF 45W IS LIMITING ITCZ ACTIVITY.

$$
RHOME






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