[Tropical] Tropical Weather Discussion

EMWIN Server emwin at nashvilleweather.net
Tue Jun 26 18:39:41 CDT 2007


AXNT20 KNHC 262335
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE JUN 26 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 34.5W S OF 16N MOVING W 12 KT.
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS NOTED
WITHIN 150 NM W AND WITHIN 180 NM E OF THE WAVE AXIS.

A TROPICAL WAVE IS ALONG 69.5W S OF 23N MOVING W AT 12 KT. UPPER
DIFFLUENCE...BETWEEN AN UPPER TROUGH NEAR THE BAHAMAS AND AN
UPPER RIDGE OVER THE NE CARIBBEAN...ENHANCED AFTERNOON
CONVECTION OVER HISPANIOLA...WESTERN PUERTO RICO AND NEAR
23N69W. THESE CONVECTIVE FLARE UPS MASK THE TRUE WAVE AXIS
POSITION. SUBSIDENCE OVER THE CENTRAL CARIBBEAN IS SUPPRESSING
CONCENTRATED CONVECTION AND ONLY TRADE WIND CUMULUS IS NOTED. AN
ELY SURGE IN THE LOW LEVEL FLOW ACCOMPANIES THIS WAVE AS WELL AS
A LARGE AREA OF SAHARAN DUST...WHICH HAS ITS WESTERN EDGE ALONG
72.5W AT THE MOMENT...AND EXTENDS E ACROSS THE WINDWARDS WITH
MOST ISLANDS REPORTING OBSTRUCTIONS TO VISIBILITY...DUR E TO
EITHER DUST OR HAZE.

A TROPICAL WAVE EXTENDS FROM COSTA RICA TO THE N COAST OF CUBA
AT 23N...ESTIMATED TO BE MOVING W AT 12 KT. SEABREEZE CONVECTION
OVER W CUBA APPEARS TO HAVE BEEN ENHANCED BY THE WAVE WITH A
CELLS PROPAGATING W INTO THE YUCATAN CHANNEL...IN THE
DISSIPATING STAGE AT THE MOMENT. A LARGE CLUSTER OF STRONG
CONVECTION IS NOTED OVER CHIRIQUI PANAMA EXTENDING W THROUGH
EASTERN COSTA RICA...AND EXTENDING N INTO THE CARIBBEAN TO NEAR
11N81W. CONCENTRATED CONVECTION...BUT ONLY TOWERING CUMULUS...
ARE OVER THE CARIBBEAN NEAR 19.5N81.5W...VERIFIED BY A LACK OF
LIGHTNING HITS.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 10N14W 8N23W 8N34W 6N54W AND IS
FOR THE MOST PART LOCATED SLIGHTLY N OF ITS ASSOCIATED CLOUDS
AND CONVECTION. OTHER THAN CONVECTION ASSOCIATED WITH THE WAVE
NEAR 35W...ONLY ISOLATED MODERATE CONVECTION IS NOTED WITHIN 180
NM S OF THE ITCZ AXIS BETWEEN 13W AND 32W AND THEN W OF THE
TROPICAL WAVE BETWEEN 38W AND 44W.

...DISCUSSION...
THE GULF OF MEXICO...
AN UPPER ANTICYCLONE HAS MOVED W ACROSS CENTRAL OLD MEXICO INTO
THE E PAC TO A POSITION NEAR 19N104W...BUT ITS ENVELOPE OF
ANTICYCLONIC FLOW STILL EXTENDS E ACROSS CENTRAL MEXICO AND OVER
THE GULF OF MEXICO TO THE W OF 91W. UPPER DEBRIS MOISTURE...THAT
ORIGINATED FROM CONVECTION OVER INTERIOR OLD MEXICO AND OVER NE
TEXAS AND THE MISSISSIPPI DELTA OF THE UNITED STATES...CONTINUES
TO SPREAD S IN THE ANTICYCLONIC FLOW TO ALONG 18N OVER BETWEEN
87W AND 95W WHERE THE MOISTURE EVAPORATES. AN UPPER TROUGH LIES
ACROSS THE CENTRAL GULF...FROM 31N85W S THROUGH A WEAK UPPER
CYCLONE AT 22N88W AND CONTINUING S OVER THE YUCATAN PENINSULA TO
BASE NEAR 17N89W. THE UPPER TROUGH HAS INDUCED A LOW LEVEL
TROUGH FROM 21N87W TO 28N84W WHICH IS MOVING W WITH TIME.
SCATTERED MODERATE CONVECTION...WITH TSTMS ACTIVITY CONCENTRATED
NEAR 25N85W BASED ON LIGHTNING DATA...ACCOMPANIES THE TROUGH.
THE NORTHERN EXTENSION OF A TROPICAL WAVE IS CURRENT MOVING
THROUGH W CUBA...AND WILL MOVE THROUGH THE YUCATAN CHANNEL
TONIGHT AND WILL LIKELY BE ACCOMPANIED BY CONVECTION ENHANCED E
OF THE UPPER TROUGH. OTHERWISE RIDGING FROM THE ATLC DOMINATES
THE LOW LEVELS.

THE CARIBBEAN SEA...
AN UPPER TROUGH EXTENDS S THROUGH THE NW BAHAMAS TO AN UPPER
CYCLONE NEAR THE YUCATAN PENINSULA AND CONTINUES S TO NEAR
BELIZE. AN UPPER ANTICYCLONE IS OVER NW VENEZUELA. THUS...THE
UPPER FLOW IS SOUTHWESTERLY OVER MOST OF THE CARIBBEAN. DEBRIS
MOISTURE...FROM CONVECTION ASSOCIATED WITH A TROPICAL WAVES OVER
THE W CARIBBEAN THE CENTRAL CARIBBEAN...AND AFTERNOON SEABREEZE
CONVECTION OVER CUBA AND HISPANIOLA...IS ADVECTED ENE INTO THE
SUBTROPICAL SW ATLC. A BAND OF DRY UPPER AIR IS INDICATED ACROSS
THE CENTRAL CARIBBEAN AND IS SUPPRESSING CONVECTION. THE LOW
LEVEL FLOW IS ELY AND QUITE BRISK...STREAMING BANDS OF TRADE
WIND CUMULUS AND BRIEF LIGHT SHOWERS...ACROSS THE AREA TO THE S
AND E OF JAMAICA. WIDESPREAD DUST IS ALSO SPREADING W ACROSS THE
AREA...CURRENTLY E OF 74W. ALTHOUGH BARBADOS IS STILL
EXPERIENCING REDUCED VISIBILITY...THE LAST HIGH RESOLUTION
VISIBLE IMAGERY OF THE DAY INDICATES THE THE EASTERN EDGE OF THE
DUST IS ALONG 58W...SO VISIBILITY CONDITIONS SHOULD IMPROVE IN
THE WINDWARDS ON WED.

THE ATLANTIC OCEAN...
AN UPPER CYCLONE HAS NEARLY CUT OFF...FROM ITS PARENT MID ATLC
UPPER TROUGH...OVER THE BAHAMAS NEAR 26N78W. AN ASSOCIATED
SURFACE LOW THAT SPUN OVER THE ATLC WATERS E OF N FLORIDA FOR
SEVERAL DAYS HAS WEAKENED INTO A SURFACE TROUGH...AND IS STILL
EVIDENT OVER THE NW BAHAMAS. BOTH SYSTEMS ARE SLOWLY SHIFTING
WESTWARD WITH TIME. INITIALLY...DRY UPPER AIR AND RESULTANT
SUBSIDENCE...WILL SUPPRESS CONVECTION OVER FLORIDA...BUT AS THE
UPPER DIFFLUENCE LOCATED OF THE UPPER LOW...MOVES OVER THE NW
BAHAMAS AND FLORIDA...CONDITIONS WILL BECOME FAVORABLE FOR AN
INCREASE IN CONVECTION...ESPECIALLY DURING AFTERNOON PEAK
HEATING. A TROPICAL WAVE OVER THE ATLC E OF THE EXTREME SE
BAHAMAS NEAR HISPANIOLA IS ALSO MOVING WESTWARD. THE NORTHERN
EXTENSION OF THIS WAVE WILL MOVE THROUGH THE BAHAMAS AND THE
STRAITS OF FLORIDA THROUGH THE REMAINDER OF THE WEEK...AND
LIKELY ALSO INCREASE THE CHANCE FOR RAIN E OF ITS AXIS.

AN UPPER RIDGE EXTENDS N FROM THE E CARIBBEAN INTO THE SW ATLC
BETWEEN 73W AND 58W AND ADVECTS UPPER DEBRIS CIRRIFORM CLOUDS NE
OVER THE SUBTROPICAL ATLC UNDER THE RIDGE. ANOTHER UPPER TROUGH
EXTENDS ACROSS THE CENTRAL ATLC INTO THE AREA FROM 31N47W TO AN
UPPER CYCLONE NEAR 19N51W WITH THE TROUGH CONTINUING S TO BASE
AT 10N56W. DRY UPPER AIR ACCOMPANIES THIS TROUGH WITHIN 150 NM
EITHER SIDE OF LINE 31N47W 23N51W AND ELSEWHERE FROM 23N TO 7N
BETWEEN 54W AND 63W. ANOTHER UPPER TROUGH IS NOTED OVER THE FAR
E ATLC ALONG 31N14W TO 23N30W. AN UPPER RIDGE EXTENDS W OFF THE
AFRICAN COAST ALONG 17N10W TO 17N20W. SCATTERED TO LOCALLY
BROKEN LOW CLOUDS ARE NOTED N OF THE ITCZ E OF 50W.

$$
NELSON



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