Tropical Weather Discussion
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000
AXNT20 KNHC 220006
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURE...

GALE WARNING BY METEO FRANCE FOR THE ZONE OF 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 60-100 NM BETWEEN STRONG HIGH PRES
OF 1035 MB WELL N OF THE DISCUSSION AREA AT 43W17W...AND LOW
PRES TO ITS E AND SE OVER NORTHERN AFRICA.

...TROPICAL WAVES...

A TROPICAL WAVE CAME OFF THE AFRICAN COAST EARLIER TODAY
EMBEDDED IN ABUNDANT LOW LEVEL MOISTURE AS INDICATED BY THE SSMI
TPW IMAGERY. SATELLITE DERIVED WINDS INDICATE A DIFFLUENT
ENVIRONMENT ALOFT WITHIN THE WAVE ENVIRONMENT...WHICH IS
SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 300 NM EITHER
SIDE OF THE WAVE AXIS LOCATED FROM 02N TO 10N NEAR 18W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE TROPICAL
ATLANTIC NEAR 10N14W TO 08N16W. IT THEN RESUMES W OF A TROPICAL
WAVE FROM 07N19W TO 06N26W WHERE THE ITCZ BEGINS AND CONTINUES
TO 04N38W TO THE NORTHERN COAST OF BRAZIL NEAR 02N51W. SCATTERED
TO ISOLATED MODERATE CONVECTION IS WITHIN 60 NM EITHER SIDE OF
THE ITCZ BETWEEN 26W AND 40W.

...DISCUSSION...

GULF OF MEXICO...

A MIDDLE TO UPPER TROUGH LOCATED OVER THE EASTERN U.S. EXTENDS S
TO A BASE OVER THE SE GULF. THIS TROUGH IS SUPPORTING A COLD
FRONT THAT EXTENDS FROM GEORGIA NEAR 30N84W...ACROSS THE FLORIDA
PANHANDLE...SOUTHERN ALABAMA AND MISSISSIPPI TO 29N92W SW TO
27N97W. LOW-LEVEL MOISTURE CONVERGENCE ALONG THE N-NW BASIN
ALONG WITH DIFFLUENCE GENERATED BY A MIDDLE LEVEL RIDGE OVER THE
WESTERN GULF SUPPORT SCATTERED MODERATE CONVECTION AND TSTMS N
OF 22N W OF 93W...SE LOUISIANA...SOUTHERN MISSISSIPPI AND
ALABAMA. WITH NO SUPPORT ALOFT...A 1017 MB HIGH CENTER CONTINUES
TO WEAKEN TONIGHT. ELSEWHERE...SATELLITE IMAGERY SHOWS A
RELATIVELY CLOUD FREE GULF. ANTICYCLONIC FLOW CONSISTING OF 5-10
KT WINDS DOMINATES ACROSS THE BASIN. 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...

THE CENTRAL AND PORTIONS OF THE EASTERN CARIBBEAN CONTINUE TO
MOISTEN DUE TO MIDDLE TO UPPER LEVEL SOUTHWESTERLY TO WESTERLY
FLOW ADVECTION OF TROPICAL MOISTURE FROM THE PACIFIC OCEAN AND
NORTHERN SOUTH AMERICA...AND ADVECTION OF ATLANTIC LOW LEVEL
TROPICAL MOISTURE BY THE TRADES. DEEP LAYER MOISTURE COMBINED
WITH A DIVERGENT ENVIRONMENT SUPPORT SCATTERED MODERATE
CONVECTION AND TSTMS OVER NICARAGUA...COSTA
RICA...PANAMA...HISPANIOLA AND ADJACENT WATERS. SIMILAR
CONVECTION IS OBSERVED OVER CENTRAL AND EASTERN CUBA BEING
ENHANCED BY A MIDDLE TO UPPER LEVEL TROUGH ACROSS THE NW
CARIBBEAN. HOWEVER...OVER THE NW BASIN DRY AND STABLE AIR IS
INDICATED BY BOTH WATER VAPOR AND SSMI TOTAL PRECIPITABLE WATER
IMAGERY...WHICH IS SUPPORTING FAIR WEATHER. A LOCALIZED TIGHT
PRES GRADIENT CONTINUES IN THE S CENTRAL CARIBBEAN BETWEEN LOW
PRES OVER NW COLOMBIA AND ATLC RIDGING N-NE OF THE AREA. THIS IS
SUPPORTING A MODERATE TO FRESH BREEZE NEAR THE NW COAST OF
COLOMBIA WITH SEAS LESS THAN 8 FT. THESE WINDS WILL CONTINUE TO
PULSE NEAR THE COAST OF COLOMBIA THE NEXT TWO DAYS BEFORE
DIMINISHING AS THE PRES GRADIENT CONTINUES TO RELAX. OTHERWISE
GENTLE TRADES AND 4-6 FT SEAS PREVAIL S OF 17N...WITH GENTLE
TRADES AND 2-4 FT SEAS N OF 17N. EXPECT SCATTERED SHOWERS AND
ISOLATED TSTMS N OF 18N TO GRADUALLY SLIDE EASTWARD OVER THE
NEXT 24-48 HRS. ELSEWHERE...LITTLE CHANGE IS FORECAST THE NEXT
TWO DAYS.

...HISPANIOLA...

DEEP LAYER MOISTURE OVER THE REGION ALONG WITH A MIDDLE LEVEL
DIVERGENT ENVIRONMENT CONTINUE TO SUPPORT SCATTERED MODERATE
CONVECTION AND TSTMS ACROSS THE ISLAND EXTENDING TO COASTAL
WATERS. THIS SCENARIO WILL LINGER INTO THE NEXT 24-36 HRS.
ACTIVITY MAY DECREASE IN COVERAGE SUN AS UPPER AIR BECOMES MORE
STABLE.

ATLANTIC OCEAN...

A SURFACE TROUGH...REMNANTS OF AN OLD FRONTAL BOUNDARY...EXTENDS
FROM NEAR 31N47W SW TO 26N50W TO 21N59W WITH ISOLATED SHOWERS
WITHIN 160 NM AHEAD OF ITS AXIS. WEST OF THE TROUGH...A 1020 MB
HIGH IS ANCHORED NEAR 28N54W...WHICH IS FORECAST TO WEAKEN
TONIGHT. SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS
EXTENDS WITHIN 75 NM OFF THE NORTHERN COASTS OF EASTERN CUBA AND
HISPANIOLA AS WELL AS N OF THE MONA PASSAGE. A 1035 MB HIGH IS
WELL NE OF THE AREA NEAR 43N17W WITH ASSOCIATED RIDGING
STRETCHING FROM IT SW TO 20N43W. HIGH PRES IS PRESENT ACROSS THE
EASTERN ATLANTIC N OF 17N E OF 47W. A COLD FRONT EXTENDING
ACROSS THE SE CONUS IS FORECAST TO MOVE INTO SW N ATLC WATERS BY
FRIDAY MORNING...DISSIPATING SUNDAY MORNING.

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

$$
NR



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