[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 192356
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE 19 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
2145 UTC.

...TROPICAL WAVES...
TROPICAL WAVE ALONG 43W S OF 19N MOVING W 5-10 KT.  THE WAVE IS
VERY CONVECTIVELY ACTIVE... ALTHOUGH WITHOUT A WELL-DEFINED
AXIS... WITH AID FROM AN UPPER LOW TO ITS W.  WIDELY SCATTERED
MODERATE FROM 10N-17N BETWEEN 36W-46W.

TROPICAL WAVE IN THE CARIBBEAN SEA ALONG 73W S OF 20N MOVING W
10-15 KT.  WLY SHEAR HAS TAKEN DISPLACED ALL OF THE CONVECTION
TO THE E OF THE WAVE AXIS WITH WIDELY SCATTERED MODERATE FROM
13N-16N BETWEEN 67W-72W.

...ITCZ...
ITCZ AXIS IS ALONG 10N14W 8N25W 12N52W 10N61W.  ISOLATED
MODERATE FROM 5N-11N BETWEEN 21W-28W.  WIDELY SCATTERED MODERATE
IS FROM 6N-9.5N BETWEEN 32W-45W.

...DISCUSSION...
GULF OF MEXICO...
THE WESTERN AND CENTRAL GULF IS EXPERIENCING UNSEASONABLY WARM
CONDITIONS WITH SLY FLOW AT THE LOW-LEVEL BRINGING MILD AIR FROM
THE RELATIVELY WARM GULF ALL ACROSS THE DEEP SOUTH.  HOWEVER AN
UPPER TROUGH ALONG THE E COAST OF THE US S OF N CAROLINA IS
DEEPENING SOME WITH UNSTABLE NW FLOW OVER ALABAMA INTO FLORIDA
CAUSING WIDELY SCATTERED MODERATE FROM 83W-87W N OF 29.5N.
OTHER PIECES OF ENERGY ARE FORECAST TO DROP INTO THE MEAN TROUGH
OFFSHORE OF FLORIDA AND SHOULD BRING A BACK-DOOR COLD FRONT THRU
FLORIDA BY FRI BUT THE REST OF THE GULF STATES SHOULD REMAIN
WARM AND MOSTLY DRY UP UNTIL THE WEEKEND.

CARIBBEAN SEA...
MID/UPPER TROUGH CONTINUES MOVING SLOWLY SOUTHWARD... NUDGING A
RIDGE THAT WAS OVER THE CENTRAL CARIBBEAN NOW OVER NW
VENEZUELA.  THIS TROUGH HAS BROUGHT DRIER AIR ALOFT OVER THE NW
CARIBBEAN BEHIND THE TROUGH AXIS FROM HISPANIOLA TO THE NE TIP
OF NICARAGUA.  ZONAL FLOW NOW DOMINATES IN THE MID/UPPER LEVELS
WITH WLY SHEAR/DIVERGENCE ENHANCING A TROPICAL WAVE IN THE
CENTRAL CARIBBEAN.  ANY INFLUENCE OF THE WEAKENED MID/UPPER HIGH
IS LIMITED S OF 12.5N WITH SHOWER ACTIVITY REDUCED IN THE SW
CARIBBEAN BUT STILL ISOLATED S OF 12.5N W OF 76W.  AN INCREASE
IN DEEP-LAYERED MOISTURE IS FORECAST OVER THE LESSER ANTILLES
INTO PUERTO RICO FOR THE NEXT COUPLE OF DAYS... WHICH SHOULD UP
THE CHANCE OF RAIN FOR THOSE ISLANDS.  THERE REMAINS A CHANCE OF
BROAD LOW DEVELOPMENT IN THE SW CARIBBEAN AROUND THE WEEKEND
WITH COMPUTER MODELS AND ENSEMBLE GUIDANCE GENERALLY AGREEING
THAT THE LOW-LEVEL FLOW WILL BECOME MORE CYCLONIC OVER THE
COMING DAYS.  THIS LOW DEVELOPMENT MIGHT BE LINKED TO AN
INCOMING ACTIVE CONVECTION PHASE OF THE MADDEN-JULIAN
OSCILLATION WHICH WILL LIKELY MIGRATE INTO THE DISCUSSION AREA
IN THE COMING DAYS.

SUBTROPICAL ATLC...
AT THE SURFACE... A DISSIPATING STATIONARY FRONT POSITIONED FROM
31N50W TO 25N62W IS SPARKING A FEW SHOWERS WITHIN 90 NM OF THE
FRONTAL BOUNDARY.   THE FRONT IS ALONG THE EASTERN PERIPHERY OF
A MEAN TROUGH IN THE W ATLC WITH ONE AXIS ALONG 31N58W TO
HISPANIOLA AND ANOTHER FROM JUST W OF BERMUDA TO THE CENTRAL
BAHAMAS.  FUTURE SHORTWAVES ARE FORECAST TO DEEPEN THE UPPER
TROUGH OVER THE W ATLC... BRINGING A NEW ROUND OF MODIFIED
CONTINENTAL AIR WITH SLIGHTLY COOLER/DRIER AIR LIKELY TO SPREAD
THRU THE CENTRAL BAHAMAS BY THE WEEKEND.   BENIGN WEATHER IS IN
PLACE THROUGHOUT THE CENTRAL ATLC WITH ANTICYCLONIC FLOW ALOFT
FROM A BUILDING HIGH IN THE DEEP TROPICS.  OTHERWISE ZONAL FLOW
HAS OVERSPREAD THE E ATLC WITH AN UPPER LOW NEAR THE AZORES
WEAKENING AND RELATIVELY DRY AIR IN THE MID/UPPER LEVELS PRESENT
E OF 30W.  BROAD CYCLONIC FLOW IS IN THE E ATLC WITH SCATTERED
LOW/MID CLOUDS N OF 26N E OF 40W.  TOWARD THE END OF THE WEEK
THE UPPER AIR PATTERN LOOKS TO BE AMPLIFYING WITH RIDGING IN THE
CENTRAL ATLC AND TWO DEEP TROUGHS IN THE W AND E ATLC.

TROPICAL ATLC...
SIMILAR TO YESTERDAY.. A CUTOFF MID/UPPER LOW IS NEAR 12N55W
WITH LITTLE MOVEMENT.  SLIGHTLY COOLER AIR ALOFT IS ENHANCING
ISOLATED SHOWERS WITHIN 120 NM OF THE LOW CENTER.  THE LOW IS
FORECAST TO DISSIPATE BY THE WEEKEND AS IT NEARS THE LESSER
ANTILLES.  OTHERWISE THE BIG STORY IS A BUILDING MID/UPPER HIGH
IN THE CENTRAL ATLC NEAR 12N38W WITH ANOMALOUS RIDGING NNE INTO
THE SUBTROPICS NEAR 20N35W.  COMPUTER MODELS ARE FORECASTING
MORE OF A SUMMER-LIKE PATTERN WITH THIS RIDGE EXPANDING WESTWARD
TO CAUSE ELY WINDS IN THE UPPER LEVELS OVER THE WINDWARD ISLANDS
BY THE WEEKEND.  THIS COULD BRIEFLY OPEN THE DOOR FOR SOMETHING
ELSE TO FORM E OF THE ISLANDS THOUGH IT IS A RATHER RARE EVENT
IN LATE OCTOBER.  LARGE AREA OF WIDELY SCATTERED SHOWERS IS
BENEATH THE RIDGE FROM 10N-17N BETWEEN 35W-46W.

$$
BLAKE

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