220
AXNT20 KNHC 210005
TWDAT
TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2330 UTC.
..TROPICAL WAVES
AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 24W/25W FROM 20N
SOUTHWARD, MOVING WEST AT 10 TO 15 KT. THE TOTAL PRECIPITABLE
WATER (TPW) SATELLITE ANIMATION SHOWS A WELL-DEPICTED PLUME OF
MOISTURE TRAILING THE WAVE BETWEEN 22W AND THE COAST OF AFRICA.
ISOLATED MODERATE RAINSHOWERS ARE FROM 10N TO 20N BETWEEN 20W AND
30W.
A CARIBBEAN SEA TROPICAL WAVE IS ALONG 71W/72W, MOVING ACROSS
HISPANIOLA. TPW IMAGERY SHOWS ENHANCED MOISTURE ASSOCIATED WITH
THIS TROPICAL WAVE. SCATTERED MODERATE TO STRONG RAINSHOWERS ARE
WITHIN 150 NM TO THE SOUTH OF HISPANIOLA BETWEEN 69W AND 73W.
SCATTERED MODERATE TO ISOLATED STRONG RAINSHOWERS ARE WITHIN 60 NM
TO THE NORTH OF HISPANIOLA BETWEEN 70W AND 73W.
THIS ACTIVITY IS CURRENTLY AFFECTING THE SOUTHERN COAST OF THE
DOMINICAN REPUBLIC. SATELLITE IMAGERY INDICATES SOME SAHARAN DUST
EAST OF THE WAVE FROM 12N-24N BETWEEN 57W-67W. PUERTO RICO AND THE
VIRGIN ISLANDS ARE REPORTING HAZY CONDITIONS. STRONG WIND GUSTS
ARE POSSIBLE NEAR SHOWERS AND STORMS ASSOCIATED WITH THIS WAVE
THROUGH FRIDAY AS IT MOVES WESTWARD THROUGH THE CENTRAL CARIBBEAN.
THE WAVE IS EXPECTED TO INCREASE THE LIKELIHOOD OF SHOWERS AND
THUNDERSTORMS OVER THE REMAINDER OF HISPANIOLA TODAY, AND ACROSS
EASTERN CUBA AND JAMAICA ON FRIDAY.
..MONSOON TROUGH/ITCZ
THE MONSOON TROUGH PASSES THROUGH THE COASTAL SECTIONS OF GUINEA
NEAR 09N13W TO 05N18W AND 05N24W. THE ITCZ CONTINUES FROM 05N24W
TO 09N45W, AND THEN FROM 09N50W TO 06N56W. SCATTERED TO NUMEROUS
STRONG RAINSHOWERS ARE ALONG THE COAST OF AFRICA FROM 05N TO 11N
BETWEEN 13W AND 19W. ISOLATED MODERATE RAINSHOWERS ARE ELSEWHERE
FROM 13N SOUTHWARD BETWEEN AFRICA AND 60W.
..DISCUSSION
GULF OF MEXICO...
WATER VAPOR IMAGERY AND MODEL ANALYSES INDICATE THE PRESENCE OF
AN UPPER-LEVEL CYCLONIC SHEAR AXIS STRETCHING FROM THE FLORIDA
STRAITS TO SOUTHEAST LOUISIANA. AT THE SURFACE, A TROUGH EXTENDS
FROM NEAR FT. MYERS, FL SOUTHWESTWARD TO NEAR 24N86W. ANOTHER
TROUGH EXTENDS THROUGH THE CENTRAL BAY OF CAMPECHE FROM 24N91W TO
THE COAST OF MEXICO NEAR 18N93W. ISOLATED SHOWERS AND THUNDERSTORMS
ARE NOTED OVER THE BAY OF CAMPECHE. THIS TROUGH AND ASSOCIATED
MOISTURE WILL MOVE WESTWARD, REACHING MAINLAND MEXICO BY LATE FRI.
A SMALL 1019 MB SURFACE HIGH IS CENTERED OVER NORTHERN FLORIDA
NEAR 30N83W.
HIGH PRESSURE BUILDING OVER THE EASTERN UNITED STATES WILL
PRODUCE MAINLY GENTLE TO MODERATE E TO SE BREEZES AND 1 TO 4 FT
SEAS ACROSS THE GULF THROUGH SUN. A TROUGH MOVING WEST ACROSS THE
SOUTHWEST GULF WILL REACH THE MEXICO COAST BY SAT. LOCALLY FRESH
WINDS ARE POSSIBLE WITH THIS TROUGH.
CARIBBEAN SEA...
A 1008 MB LOW ALONG THE MONSOON TROUGH IS LOCATED IN THE
SOUTHWEST CARIBBEAN NEAR 11N82W. THESE FEATURES ARE PRODUCING
NUMEROUS MODERATE TO STRONG CONVECTION OVER THE SOUTHWEST
CARIBBEAN FROM 10N-13N BETWEEN 77W-86W. THIS ACTIVITY IS AFFECTING
PARTS OF NORTHERN COSTA RICA AND NICARAGUA, INCLUDING THE CITY OF
BLUEFIELDS, WHERE HEAVY THUNDERSTORMS ARE CURRENTLY BEING
REPORTED. PLENTY OF MOISTURE WILL PERSIST OVER THE SOUTHWEST
CARIBBEAN THROUGH SATURDAY AS THE TROPICAL WAVE, CURRENTLY ALONG
70W, REACHES THE AREA AND MOVES INLAND INTO CENTRAL AMERICA LATE
SAT OR EARLY SUN.
A TROPICAL WAVE ALONG 71W-72W WILL MOVE WEST ACROSS THE CENTRAL
CARIBBEAN THROUGH FRI, AND THEN OVER CENTRAL AMERICA SUN. STRONG
WIND GUSTS ARE POSSIBLE NEAR SHOWERS AND THUNDERSTORMS ASSOCIATED
WITH THIS TROPICAL WAVE ACROSS THE EASTERN CARIBBEAN THROUGH FRI.
MEANWHILE, HIGH PRESSURE BUILDING FROM THE CENTRAL ATLC INTO THE
CENTRAL BAHAMAS WILL SUPPORT MODERATE TO FRESH TRADE WINDS AND
BUILDING SEAS ACROSS THE ENTIRE BASIN NOW THROUGH FRI, BEFORE
WINDS DIMINISH SLIGHTLY SAT AND THEN MORE SIGNIFICANTLY ON SUN.
ATLANTIC OCEAN...
A 1012 MB SURFACE LOW, FORMERLY A TROPICAL WAVE, IS PRODUCING A
CONCENTRATED AREA OF THUNDERSTORMS NEAR 10.5N49W, OR ABOUT 740 NM
EAST OF THE WINDWARD ISLANDS. ALTHOUGH THIS DISTURBANCE SHOWS
SOME SIGNS OF ORGANIZATION ON SATELLITE IMAGERY, THERE IS NO
EVIDENCE OF A SURFACE CIRCULATION AT THIS TIME. A RECENT ASCAT
PASS CONFIRMS THE PRESENCE OF AN OPEN TROUGH. SCATTERED MODERATE
CONVECTION IN A BANDING PATTERN IS NOTED FROM 10N-13N BETWEEN 46W-
50W. SOME ADDITIONAL DEVELOPMENT IS POSSIBLE TODAY BEFORE UPPER-
LEVEL WINDS BECOME HIGHLY UNFAVORABLE FOR TROPICAL CYCLONE
FORMATION STARTING TONIGHT AND CONTINUING THROUGH THE WEEKEND.
THE REMNANT OF JOYCE IS ANALYZED AS A 1014 MB LOW NEAR 30N32W. A
TROUGH EXTENDS FROM THE LOW TO 26N34W. NO SIGNIFICANT CONVECTION
IS NOTED.
A COLD FRONT ENTERS THE FORECAST AREA NEAR 31N69W AND CONTINUES
SOUTHWESTWARD TO 29N73W TO 29N79W. SCATTERED SHOWERS ARE WITHIN
120 NM AHEAD OF THE FRONTAL BOUNDARY BETWEEN 70W-78W. EAST OF THE
FRONT, A SURFACE TROUGH IS ANALYZED FROM 29N62W TO 23N70W.
SCATTERED SHOWERS AND THUNDERSTORMS ARE LOCATED WITHIN 150 NM EAST
OF THE TROUGH. SCATTEROMETER DATA INDICATE WINDS OF 20-25 KT ARE
CURRENTLY OCCURRING NORTH OF 29N BETWEEN 64W-69W. THIS AREA OF
20-25 KT WINDS WILL MOVE EASTWARD OVER THE AREA FOR THE NEXT 12
HOURS BEFORE GRADUALLY WEAKENING. THE AFOREMENTIONED FRONT WILL
SINK SE TO THE WATERS NORTH OF 27N THROUGH FRI BEFORE THE FRONT
DISSIPATES.
LOW PRESSURE MOVING OFF THE CAROLINAS OVERNIGHT HAS DRAGGED A
WEAK EARLY SEASON FRONTAL BOUNDARY FROM 31N66W TO 29N79W. THE
FRONT WILL SINK SE TO WATERS NORTH OF 27N THROUGH FRI BEFORE THE
FRONT DISSIPATES. THE LOW WILL MOVE SE TO NEAR 29N66W BY SAT
MORNING THEN DRIFT W AND SHOULD SLOWLY WEAKEN THROUGH MON. NE
SWELL WILL MOVE INTO THE OPEN WATERS EAST OF THE BAHAMAS FRI
THROUGH EARLY NEXT WEEK.
FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE
HAGEN/GR/AL/MT
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