Tropical Weather Discussion
Issued by NWS

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000
AXNT20 KNHC 211758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU MAY 21 2015

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURE...

THE GALE WARNING METEO FRANCE ISSUED EARLIER THIS MORNING FOR
ZONE AGADIR ALONG THE COAST OF MOROCCO REMAINS IN EFFECT.
BEAFORT 7-8 OR 32 TO 46 KT WINDS ARE FORECAST FOR THIS ZONE AS
VERY TIGHT PRES GRADIENT WITH ISOBARIC SPACING OF ONLY 100-120
NM BETWEEN STRONG HIGH PRES OF 1036 MB WELL N OF THE DISCUSSION
AREA AT 43W17W...AND LOW PRES TO ITS E AND SE OVER NORTHERN
AFRICA REMAIN IN PLACE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE TROPICAL
ATLANTIC NEAR 10N14W TO 6N21W WHERE IT TRANSITIONS TO THE ITCZ
ITCZ AND CONTINUES TO 2N40W TO 05N30W AND TO THE COAST OF S
AMERICA NEAR 01N50W. SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION IS S OF THE MONSOON TROUGH FROM 2N-10N BETWEEN 9W-
20W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION
ARE SEEN WITHIN 120 NM NW OF THE MONSOON TROUGH BETWEEN 16W-19W.
SCATTERED MODERATE CONVECTION IS WITHIN 180 NM S OF THE MONSOON
TROUGH BETWEEN 16W-18W...AND WITHIN 60 NM OF THE ITCZ BETWEEN
22W-28W.

...DISCUSSION...

GULF OF MEXICO...
THE TAIL END OF AN UPPER TROUGH LOCATED OVER THE EASTERN U.S.
EXTENDS SW TO THE NE GULF...AND SW TO NEAR 26N88W. BROAD UPPER
RIDGING HAS MOVED EASTWARD TO THE WESTERN PART OF THE GULF.
UPPER NORTHWESTERLY FLOW BETWEEN BOTH OF THESE FEATURES IS
PRESENT E OF 93W. THE DAILY NOCTURNAL TROUGH THAT FORMS NEAR THE
NW YUCATAN PENINSULA HAS MIGRATED WESTWARD TO ALONG 93W S OF
22N. SATELLITE IMAGERY SHOWS A RELATIVELY CLOUD FREE GULF...WITH
ONLY MINIMAL SCATTERED LOW CLOUDS THROUGHOUT N OF 22N. THE
EXCEPTION IS ACROSS EASTERN TEXAS...AND COASTAL WATERS. BOTH
DOPPLER RADAR AND SATELLITE IMAGERY SHOW SCATTERED STRONG
CONVECTION IN MCS TYPE FASHION PUSHING SSE ACROSS SOUTHERN TEXAS
AND THE COASTAL WATERS THERE...WHILE SCATTERED SHOWERS AND
ISOLATED TSTMS ARE DEVELOPING ELSEWHERE OVER EASTERN TEXAS AND
ITS COASTAL WATERS. THIS IS PRIMARILY DUE TO THE FOCUS OF A
SURFACE COLD FRONT ACROSS EASTERN TEXAS COMPILED WITH MOIST AND
UNSTABLE AIR MASS IN PLACE AND POSSIBLE UPPER LEVEL DISTURBANCES
RIDING SE ACROSS THE UPPER RIDGING.

AS OF 15 UTC...A 1018 MB HIGH CENTER AT 27N87W IS KEEPING AN
ANTICYCLONIC FLOW CONSISTING OF 5-10 KT WINDS E OF ABOUT
90W...SE FLOW OF 10-15 KT IS TO THE W OF 90W...EXCEPT FOR WINDS
E-SE IN DIRECTION S OF 22N W OF 90W. THE 1017 MB HIGH IS FORECAST
TO DISSIPATE IN ABOUT 24 HRS...WHILE THE AFOREMENTIONED COLD
FRONT SHOULD EXTEND FROM NEAR FROM NEAR W CENTRAL FLORIDA NW TO
SE LOUISIANA WHERE IT BECOMES STATIONARY WSW FROM THERE TO
INLAND VICINITY CENTRAL TEXAS. SIMILAR UNSETTLED WEATHER SHOULD
CONTINUE IN ASSOCIATION WITH THE EARLIER MENTIONED FRONT...WITH
SIMILAR WEATHER EXPECTED TO DEVELOP ALONG AND INLAND THE N
CENTRAL GULF FRI INTO SAT FURTHER AIDED BY AN UPPER LEVEL
DISTURBANCE PASSING ACROSS THOSE AREAS. OTHERWISE...THE UPPER
RIDGE IS FORECAST TO COVER JUST ABOUT THE ENTIRE GULF BY SAT.

CARIBBEAN SEA...

A 1009 MB LOW IS CENTERED OVER NW COLOMBIA NEAR 10N75W. THE
SURFACE ANALYSIS HAS A RATHER WEAK PRES GRADIENT THROUGHOUT
...WITH THE EXCEPTION OF THE S CENTRAL AND SW PORTIONS WHERE THE
STRONGER THERE SUPPORTS NE-E WINDS OF 15-25 KT TRADE WINDS WITH
THE HIGHEST OF THESE ALONG THE NORTHERN COAST OF COLOMBIA AND
WEAKEST WINDS ALONG THE S COAST OF CUBA. WATER VAPOR IMAGERY
INDICATES BROAD UPPER RIDGING PERSISTING ACROSS THE CARIBBEAN E
OF CENTRAL AMERICA...WHILE W OF THERE AN UPPER TROUGH EXTENDS
FROM THE WESTERN TIP OF CUBA SW TO GUATEMALA...AND CONTINUES TO
THE EASTERN PACIFIC. UPPER LEVEL DIVERGENCE SE OF THE UPPER
TROUGH IS AIDING CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION SEEN SW OF A LINE FROM NE NICARGAGUA TO 10N76W.
ELSEWHERE...ONLY ISOLATED SHOWERS AND TSTMS ARE NOTED ELSEWHERE
PRIMARILY E OF 81W...EXCEPT FOR SCATTERED SHOWERS AND ISOLATED
TSTMS ENHANCED BY A SMALL UPPER DISTURBANCE IN THE SW FLOW AHEAD
OF THE UPPER TROUGH NOTED N OF 18N E OF JAMAICA INCLUDING THE
WINDWARD PASSAGE. WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG
STRONG SUBSIDENCE FILTERING EASTWARD ACROSS THE NW CARIBBEAN
ALLOWING FOR GENERALLY CLOUD FREE SKIES THERE. ONLY SMALL LINES
OF LOW CLOUDS WITH POSSIBLE ISOLATED SHOWERS ARE SEEN MOVING
WESTWARD OVER THAT PART OF THE SEA. EXPECT THE SCATTERED SHOWERS
AND ISOLATED TSTMS N OF 18N TO GRADUALLY SLIDE EASTWARD OVER THE
NEXT 24-48 HRS. ELSWHERE...LITTLE CHANGE IS FORECAST OVER THE
NEXT 24-48 HRS.

...HISPANIOLA...

SCATTERED SHOWERS AND ISOLATED TSTMS AS DESCRIBED UNDER THE
CARIBBEAN SECTION ARE APPROACHING HAITI FROM THE WINDWARD
PASSAGE. SATELLITE IMAGERY SHOWS SCATTERED SHOWERS AND TSTMS
DEVELOPING OVER THE INTERIOR PORTIONS OF THE ISLAND WHERE
OROGRAPHIC LIFTING AS AFTERNOON DAYTIME HEATING GETS UNDER WAY.
IN ADDITION...PLENTY OF AVAILABLE MOISTURE AND INSTABILITY
THERE IS FURTHER FUELED BY ENERGY FROM THE APPROACHING UPPER
TROUGH DESCRIBED ABOVE. THIS SCENARIO WILL LINGER INTO THE NEXT
24-36 HRS. ACTIVITY MAY DECREASE IN COVERAGE SUN AS UPPER AIR
BECOMES MORE STABLE.

ATLANTIC OCEAN...

AN UPPER LEVEL LOW IS CENTERED OVER THE W ATLANTIC NEAR 30N67W.
ANOTHER UPPER LEVEL LOW IS CENTERED OVER THE CENTRAL ATLANTIC N
OF OF THE AREA NEAR 35N44W...AND IS LIFTING NE. AN ASSOCIATED
SURFACE TROUGH EXTENDS FROM THE SURFACE LOW AT 36N50W 1013 S TO
31N48W. A 1019 MB HIGH IS OVER THE W ATLANTIC NEAR 28N59W WITH A
RIDGE SW TO THE CENTRAL BAHAMAS. A SURFACE TROUGH...REMNANTS OF
AN OLD FRONTAL BOUNDARY...EXTENDS FROM NEAR 31N46W SW TO 24N55W
TO JUST NE OF PUERTO RICO AS OF 12 UTC THIS MORNING. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE WITHIN 60 NM OF THE TROUGH E OF
61W...AND ISOLATED SHOWERS ARE WITHIN 90 NM OF THE TROUGH W OF
61W. A 1036 MB HIGH IS WELL NE OF THE AREA NEAR 43N17W WITH
ASSOCIATED RIDGING STRETCHING FROM IT SW TO 22N45W. HIGH PRES IS
PRESENT ACROSS THE EASTERN ATLANTIC N OF 18N E OF 43W. A THIRD
UPPER LEVEL LOW IS CENTERED OVER THE E ATLANTIC NEAR 26N23W. THE
UPPER LOW NEAR 30N67W IS FORECAST TO MOVE ESE OVER THE NEXT 48
HRS WHILE WEAKENING TO A TROUGH AS THE UPPER RIDGING OVER THE
GULF OF MEXICO SLIDES EASTWARD TO THE WESTERN ATLANTIC AND
BAHAMAS.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
AGUIRRE



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