[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 192308
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI AUG 19 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA... GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2245 UTC.

...TROPICAL WAVES...

CENTRAL ATLC WAVE ALONG 35W S OF 21N MOVING W 15 KT.  THIS IS A
RATHER LARGE WAVE WITH A CIRCULATION THAT ENCOMPASSES THE ATLC S
OF 21N BETWEEN THE CAPE VERDES AND 45W.  IT APPEARS THAT THE
MAIN AXIS IS A LITTLE FARTHER W THAN EARLIER... NEAR AN INCREASE
IN LOW/MID CLOUDINESS.  A WEAK SURFACE TROUGH WAS SPAWNED FROM
THE TROPICAL WAVE AND IS NOW ALONG 29W BETWEEN 14N AND 23N WITH
A LOW/MID ROTATION NOTED AT THE N END OF THE TROUGH.  THE GFS
SUGGESTS THE WAVE WILL BECOME LESS DISTINCT WITH TIME WITH
SURFACE AND MID-LEVEL CENTERS THAT ARE NOT WELL-ALIGNED.  THE
FIRST ENHANCED MOISTURE FROM THE WAVE COULD REACH THE E
CARIBBEAN EARLY NEXT WEEK.  FOR NOW THE WAVE REMAINS WITHOUT
SIGNIFICANT CONVECTION PROBABLY IN PART TO VERY DRY AIR IN THE
MID/UPPER LEVELS SEEN ON WATER VAPOR PICTURES.

TROPICAL WAVE IS IN THE LESSER ANTILLES ALONG 61W S OF 17N
MOVING W 10-15 KT.  THE WAVE IS ENHANCING WIDELY SCATTERED
SHOWERS AND FEW TSTMS S OF 14N E OF 65W IN THE CARIBBEAN.  THIS
MOISTURE SHOULD INCREASE THE CHANCE OF RAIN IN THE E CARIBBEAN
WATER THRU TOMORROW.

W CARIBBEAN WAVE IS ALONG 88W S OF 20N MOVING W 15 KT.  VISIBLE
SATELLITE SHOWED DECENT CYCLONIC CURVATURE IN THE LOW-CLOUDS IN
THE GULF OF HONDURAS THIS AFTERNOON IN ADDITION TO TSTMS IN THE
EPAC ALSO CORRESPONDING TO THE WAVE LOCATION.  WIDELY SCATTERED
TSTMS ARE OVER W HONDURAS NW THRU GUATEMALA WITH THE WAVE.  THIS
WAVE SHOULD BRING A HIGH CHANCE OF TSTMS TO YUCATAN WESTWARD
THRU THE ISTHMUS OF TEHAUNTEPEC TOMORROW.

...ITCZ...

ITCZ AXIS IS ALONG 15N17W 9N35W 8N45W 12N58W.  SCATTERED
MODERATE CONVECTION FROM 9N-16N E OF 20W.  WIDELY SCATTERED
MODERATE CONVECTION WITHIN 75 NM OF AXIS FROM 20W-30W.  ISOLATED
MODERATE CONVECTION WITHIN 60 NM OF AXIS FROM 30W-48W AND FROM
52W-56W.

...DISCUSSION...

GULF OF MEXICO...
NOW THAT A MID/UPPER LOW IS INLAND OVER S TEXAS... THE GULF IS
DOMINATED BY A LARGE HIGH OVER THE SE UNITED STATES WITH
ANTICYCLONIC FLOW ALOFT.  MODERATE/STRONG SUBSIDENCE IS LIMITING
MOST TSTMS TO BE ISOLATED IN NATURE EXCEPT OVER LAND.  THIS HIGH
SHOULD BE THE CONTROLLING FORCE FOR THE NEXT SEVERAL DAYS WITH
GENERAL ELY FLOW AND ONLY A FEW MARITIME TSTMS SAVE NEAR THE
COAST.  THE BAY OF CAMPECHE COULD BE SLIGHTLY MORE STORMY AS AN
UPPER LOW FROM THE CARIBBEAN WILL MOVE OVER NW CENTRAL AMERICA
AND INCREASE THE CHANCE OF RAIN FOR YUCATAN... WHICH MEANS LARGE
CLUSTERS OF TSTMS COULD MOVE OVER THE AREA IN THE LATE AFTERNOON
OR EVENING HOURS.  GRADUALLY INCREASING MOISTURE MIGHT UP THE
CHANCE OF RAIN SLIGHTLY OVER THE SRN GULF S OF 24N OVER THE NEXT
DAY OR TWO WITH ANOTHER CONCENTRATION OF TSTMS POSSIBLE OVER N
FLORIDA.

CARIBBEAN SEA...
INVERTED UPPER TROUGH IS FROM NW HONDURAS THRU JAMAICA THEN INTO
THE WINDWARD PASSAGE.  THE FEATURE LOOKS TO BE BREAKING UP WITH
A LOW POSSIBLY FORMING IN THE GULF OF HONDURAS AND NEAR THE
WINDWARD PASSAGE.  A STRONG MID-LEVEL ROTATION IS NOTED NEAR
16N83W MOVING SLOWLY WESTWARD AND COULD BE RESPONSIBLE FOR SOME
SCATTERED TSTMS FROM 13N-18N BETWEEN 81W-84W.  ALTHOUGH IT HAS
NO SURFACE REFLECTION.. THIS PIECE OF ENERGY WILL HAVE TO BE
WATCHED AS IT HEADS INTO THE W CARIBBEAN TOMORROW AND PERHAPS
INTO THE BAY OF CAMPECHE LATER IN THE WEEKEND WITH AN UPPER
ENVIRONMENT THAT ISN'T TOO HOSTILE.  THE BRUNT OF THE MOISTURE
SHOULD BE INLAND BY SUN PERHAPS BRINGING DRIER WEATHER TO NW
CARIBBEAN LATE IN THE WEEKEND.  FARTHER E... ANOTHER INVERTED
TROUGH LIES FROM TRINIDAD TO 17N65W AND COMBINED WITH A TROPICAL
WAVE BROUGHT A FAIRLY WET DAY TO THE WINDWARD ISLANDS.  MODERATE
SUBSIDENCE IS WEST OF THE TROUGH WITH A RATHER LARGE DRY SPOT S
OF 15N TO S AMERICA BETWEEN 70W-80W.  MUCH DRIER AIR ALOFT IS
LIKELY TO OVERSPREAD THE LESSER ANTILLES TOMORROW AND SHOULD
REDUCE THE CHANCE OF WIDESPREAD CONVECTION.  HOWEVER WITH
PLENTIFUL LOW-LEVEL MOISTURE AND DEEP ELY FLOW.. TYPICAL
TRADEWIND SHOWERS ARE PROBABLE.

ATLANTIC OCEAN...
AN UPPER HIGH CENTERED OVER THE SE USA CONTROLS THE WEATHER W OF
75W N OF 25.. GENERALLY DRIER THAN AVERAGE.  HOWEVER AN INVERTED
TROUGH EXTENDS FROM THE WINDWARD PASSAGE TO 29N64W HERALDING AN
INCREASE IN DEEP MOISTURE.  BEHIND THIS MID/UPPER TROUGH LIES
THE REMNANTS OF T.D. TEN...NOW A SURFACE TROUGH FROM NEAR THE
MONA PASSAGE TO 23N69W.  TSTM ACTIVITY IS CONSIDERABLE E OF THE
TROUGH WITH A SCATTERED AREA FROM 20N-23N BETWEEN 63W-67W.
COMPUTER MODELS ARE FORECASTING THE LOW-LEVEL RIDGE TO REMAIN
STRONG ENOUGH TO STEER THE TROUGH ON A GENERAL WNW TRACK TOWARD
THE FLORIDA STRAITS.  A FEW MODELS ALSO HINT AT REDEVELOPMENT
BUT THIS DOES NOT SEEM LIKELY AS LONG AS THE LOW-LEVEL TROUGH
STAYS TO THE W OF MOST OF THE TSTMS.  AN UPPER HIGH IS BEHIND
THE TROUGH... CENTERED NEAR 26N57W.  A FEW TSTMS N FROM 26N-31N
BETWEEN 56W-66W... A BIT OF MOISTURE TRAPPED BENEATH THE RIDGE
NEAR AN OLD SURFACE TROUGH.  FARTHER E... AN UPPER LOW IS NEAR
27N43W AND IS DRIFTING WESTWARD WITH TROUGH AXIS SSW TO 20N45W.
THE GFS SUGGEST THE FEATURE WILL MOVE SLOWLY W OR NW DURING THE
NEXT DAY OR TWO WITH ONLY A SMALL INTRUSION INTO THE DEEP
TROPICS S OF 20N.  VERY DRY AIR ALOFT CONTINUES E OF THE LOW N
OF 15N BETWEEN 30W-40W.  OTHERWISE IN THE AREA...  AN UPPER HIGH
IS NEAR 19N20W WITH RIDGE AXIS WSW TO 15N40W 12N50W.  S OF THE
RIDGE AXIS... FAIRLY MOIST AIR IS PRESENT ALOFT WITH STRONG
SUBSIDENCE DRYING N OF THE AXIS.  SCATTERED TSTMS ARE PRESENT N
OF 9N TO 17N E OF 20W FROM THE NEXT WAVE OVER W AFRICA.
COMPUTER MODELS ARE A LITTLE MORE SPLIT THAN YESTERDAY ON
WHETHER THIS WAVE WILL DEVELOP IN THE E ATLC...W ATLC.. OR EVEN
AT ALL.  AT THE SURFACE... SURFACE RIDGE LIES FROM 33N45W INTO A
1022 MB HIGH NEAR 29N59W.  THE LARGE BROAD TROPICAL WAVE IN THE
CENTRAL ATLC SEEMS TO HAVE INCREASED THE TRADES SLIGHTLY N OF
20N BUT WEAKENED THEM CONSIDERABLY S OF 20N E OF 45W.  THE
TRADES SHOULD WEAKEN NEAR THE LESSER ANTILLES DURING THE WEEKEND
AS THE WAVE NEARS THE AREA.

$$
BLAKE


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