914
AXNT20 KNHC 201205
TWDAT
TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU SEP 20 2018
TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA, CENTRAL AMERICA
GULF OF MEXICO, CARIBBEAN SEA, NORTHERN 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1145 UTC.
..TROPICAL WAVES
A FAR EASTERN ATLANTIC TROPICAL WAVE HAS ITS AXIS ALONG 21W/23W
FROM 05N25N TO 14N24W TO 20N23W, MOVING WESTWARD AT 10 TO 15 KT.
THIS WAVE IS SUPPORTED BY A 700 MB INVERTED-TROUGH FROM 14N TO
20N. OM 20N SOUTHWARD. THIS WAVE IS ASSOCIATED WITH A DISTINCT 700
MB TROUGH FROM 13N TO 20N. IN ADDITION, MID-LEVEL SATELLITE
WINDS SHOW WINDS VEERING IN DIRECTION FROM NE TO SE ACROSS THE
WAVE AXIS. THE TOTAL PRECIPITABLE WATER (TPW) SATELLITE ANIMATION
SHOWS A WELL-DEPICTED PLUME OF MOISTURE TRAILING THE WAVE TO THE
COAST OF AFRICA.
A FAR EASTERN ATLANTIC SURFACE TROUGH IS ANALYZED FROM 10N31W TO
19N30W, MOVING WESTWARD AT ABOUT 10 KT. THE TROUGH CONTINUES
TO BE REFLECTED AT 700 MB AS A RATHER DISTINCT INVERTED TROUGH.
700 MB TROUGH. NO DEEP CONVECTION IS SEEN WITH THE TROUGH, ONLY
ISOLATED SHOWERS AND THUNDERSTORMS WITHIN 60 NM EITHER SIDE OF THE
A 1010 MB LOW, FORMERLY A TROPICAL WAVE, IS ANALYZED NEAR 10N48W,
MOVING WESTWARD AT 10 TO 15 KT. THE OVERALL CLOUD PATTERN OF THIS
LOW APPEARS MORE SYMMETRIC THAN 18 TO 24 HOURS AGO. SATELLITE
IMAGERY SHOWS SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120
NM OF THE LOW IN THE NORTHERN SEMICIRCLE. SCATTERED MODERATE
CONVECTION IS WITHIN 90 NM OF THE LOW IN THE SOUTHERN SEMICIRCLE.
LATEST NHC TROPICAL WEATHER OUTLOOK CALLS FOR SOME DEVELOPMENT
OF THIS SYSTEM TODAY BEFORE BEFORE UPPER-LEVEL WINDS BECOME
HIGHLY UNFAVORABLE FOR TROPICAL CYCLONE FORMATION STARTING TONIGHT
AND CONTINUING THROUGH THE WEEKEND.
AN EASTERN CARIBBEAN SEA TROPICAL WAVE HAS ITS AXIS ALONG 69W
SOUTH OF 20N TO INLAND VENEZUELA AT 09N. IT IS MOVING WESTWARD AT
10 TO 15 KT. SATELLITE IMAGERY SHOWS A RATHER LARGE AREA OF
SCATTERED SHOWERS SHOWERS AND THUNDERSTORMS EAST OF THE WAVE NORTH
OF 15N AND BETWEEN THE WAVE AND 65W. THE TPW ANIMATION CONCURS
WITH THIS SHOWER AND THUNDERSTORM ACTIVITY IN DEPICTING LOW-LEVEL
OVER THE EASTERN CARIBBEAN SEA. SATELLITE IMAGERY INDICATES SOME
SAHARAN DUST IN THE WAKE OF THE WAVE OVER THE FAR EASTERN
CARIBBEAN SEA AND TROPICAL ATLANTIC BETWEEN THE LESSER ANTILLES
AND 55W. THE DUST IS FORECAST TO CONTINUE TO SPREAD WESTWARD,
ACROSS THE EASTERN CARIBBEAN SEA ISLANDS, BRINGING HAZY SKIES AND
STABLE CONDITIONS THROUGH EARLY SAT.
..MONSOON TROUGH/ITCZ
THE MONSOON TROUGH AXIS EXTENDS OFF THE COASTAL SECTIONS OF
SENEGAL NEAR 13N17W TO 12N21W. THE ITCZ AXIS EXTENDS FROM 10N24W
TO 08N33W TO 06N44W. SCATTERED MODERATE CONVECTION IS NOTED FROM
04N TO 10N BETWEEN 11N AND 20W, AND WITHIN 180 NM SOUTH OF THE
ITCZ BETWEEN 28W AND 31W. SCATTERED MODERATE CONVECTION IS TO THE
NORTHWEST OF THE ITCZ WITHIN 60 NM OF LINE FROM 09N51W TO 09N60W.
..DISCUSSION
GULF OF MEXICO...
UPPER LEVEL-CYCLONIC WINDS COVER FLORIDA AND THE NE CORNER OF THE
GULF OF MEXICO.
AN UPPER-LEVEL TROUGH IS IN MEXICO AND SOUTH TEXAS. MIDDLE LEVEL
AND UPPER- LEVEL CLOUDS ARE OFF THE COAST FROM NE MEXICO TO SOUTH
TEXAS.
A SURFACE TROUGH, THE REMNANT OF ISAAC, IS IN THE EASTERN PART OF
THE YUCATAN PENINSULA. EARLIER SCATTERED TO NUMEROUS STRONG
CONVECTION THAT WAS OVER THE WESTERN SECTIONS OF THE YUCATAN
PENINSULA, HAVE WEAKENED AND DISSIPATED, AND MOVED OFFSHORE.
ISOLATED MODERATE TO LOCALLY STRONG RAINSHOWERS ARE IN THE ISTHMUS
OF TEHUANTEPEC OF SOUTHERN MEXICO AND NEIGHBORING WATERS, FROM
21N SOUTHWARD BETWEEN LAND AND 94W.
HIGH PRESSURE WILL BUILD ACROSS THE EASTERN UNITED STATES
THROUGH TONIGHT. THIS WILL ALLOW GENTLE TO MODERATE E TO SE
BREEZES AND 2 TO 4 FT SEAS ACROSS THE GULF OF MEXICO THROUGH
SUNDAY. A SURFACE TROUGH, THAT IS IN THE NW CARIBBEAN SEA AND THE
YUCATAN CHANNEL, WILL SHIFT WESTWARD ACROSS THE SOUTH CENTRAL GULF
OF MEXICO AND THE YUCATAN PENINSULA THROUGH TONIGHT, AND ACROSS
THE SOUTHWEST GULF OF MEXICO ON THURSDAY AND FRIDAY, BEFORE
DISSIPATING SAT.
CARIBBEAN SEA...
AN UPPER-LEVEL TROUGH PASSES THROUGH THE ATLANTIC OCEAN, THROUGH
THE WINDWARD PASSAGE, INTO THE SW CORNER OF THE CARIBBEAN SEA NEAR
THE COASTS OF COSTA RICA AND PANAMA. ISOLATED SHOWERS AND
THUNDERSTORMS ARE SEEN FROM NORTH OF 16N AND WEST OF 79W,
AN EASTERN CARIBBEAN SEA TROPICAL WAVE, ALONG 69W, WILL MOVE
WESTWARD, ACROSS THE CENTRAL CARIBBEAN SEA THROUGH
FRI. THE WAVE WILL PASS TO THE WEST OF THE AREA THROUGH LATE
SATURDAY INTO SUNDAY. STRONG GUSTS ARE POSSIBLE NEAR RAINSHOWERS,
THAT ARE ASSOCIATED WITH THIS TROPICAL WAVE NEAR THE LESSER
ANTILLES AND EASTERN CARIBBEAN SEA THROUGH THIS EVENING. HIGH
PRESSURE BUILDING FROM THE CENTRAL ATLANTIC OCEAN INTO THE CENTRAL
BAHAMAS WILL SUPPORT MODERATE TO FRESH TRADE WINDS AND BUILDING
SEAS ACROSS THE ENTIRE BASIN FROM LATE ON WEDNESDAY THROUGH
FRIDAY.
ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH IS ABOUT 800 NM TO 850 NM TO THE ESE OF THE
COAST OF THE U.S.A. AN ASSOCIATED CYCLONIC CIRCULATION CENTER IS
ABOUT 130 NM TO THE ENE OF BERMUDA. 24-HOUR RAINFALL TOTALS THAT
ARE LISTED FOR THE PERIOD THAT ENDED AT 20/0000 UTC, ACCORDING TO
THE PAN AMERICAN TEMPERATURE AND PRECIPITATION TABLES,
MIATPTPAN/SXCA01 KNHC...ARE 2.20 IN BERMUDA. THE TROUGH EVENTUALLY
PASSES THROUGH THE WINDWARD PASSAGE, INTO THE SW CORNER OF THE
CARIBBEAN SEA NEAR THE COASTS OF COSTA RICA AND PANAMA. ISOLATED
TO WIDELY SCATTERED MODERATE AND LOCALLY STRONG RAINSHOWERS COVER
THE ATLANTIC OCEAN FROM 20N NORTHWARD BETWEEN 50W AND 65W.
A SECOND UPPER LEVEL TROUGH IS MOVING FROM THE U.S.A. MIDDLE
ATLANTIC STATES SOUTHEASTWARD. A COLD FRONT IS ABOUT 400 NM TO THE
EAST OF THE U.S.A. THE COLD FRONT PASSES THROUGH 32N72W TO
29N80W. ISOLATED MODERATE RAINSHOWERS COVER THE WATERS THAT ARE
FROM 29N NORTHWARD FROM 65W WESTWARD.
THE REMNANT LOW PRESSURE CENTER OF JOYCE IS A 1013 MB LOW PRESSURE
CENTER THAT IS NEAR 30N30W. RAINSHOWERS ARE POSSIBLE FROM 25N TO
32N BETWEEN 27W AND 38W, IN A SWIRL OF LOW LEVEL AND MIDDLE LEVEL
CLOUDS.
AN UPPER LEVEL TROUGH EXTENDS FROM A CYCLONIC CIRCULATION CENTER
THAT IS NEAR 33N23W, TO A SECOND CYCLONIC CIRCULATION CENTER THAT
IS NEAR 27N37W, TO A THIRD CYCLONIC CIRCULATION CENTER THAT IS
NEAR 15N52W, TO 12N59W. RAINSHOWERS ARE POSSIBLE FROM 20N BETWEEN
20W AND 50W.
A SURFACE TROUGH, REACHING FROM BERMUDA TO 27N74W, WILL SHIFT NW
AND DISSIPATE TONIGHT AS THE CENTRAL ATLANTIC OCEAN RIDGE BUILDS
INTO THE SOUTHERN BAHAMAS. LOW PRESSURE MOVING OFF THE CAROLINAS
TONIGHT WILL DRAG A WEAKENING FRONTAL BOUNDARY ACROSS THE WATERS
NORTH OF 27N ON THURSDAY AND FRIDAY. THE LOW WILL SINK TO NEAR
31N67W ON FRIDAY EVENING. IT WILL DRIFT W, AND SLOWLY WEAKEN ON
SATURDAY AND SUNDAY. NE SWELL WILL MOVE INTO THE OPEN WATERS EAST
OF THE BAHAMAS FROM FRIDAY THROUGH THE EARLY PARTS OF THE NEXT
WEEK.
FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE
MT/AGUIRRE
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