Tropical Weather Discussion
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000
AXNT20 KNHC 211756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT MAR 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
1630 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 6N11W TO
NEAR 4N21W. THE ITCZ EXTENDS FROM 0NS23W TO THE COAST OF SOUTH
AMERICA NEAR 3S40W. SCATTERED MODERATE TO STRONG CONVECTION IS
OCCURRING WITHIN 150 NM S OF THE AXIS E OF 20W...AND FROM 0N-6S
BETWEEN 30W AND 46W.

...DISCUSSION...

GULF OF MEXICO...
BROAD AND PERSISTENT UPPER RIDGE DOMINATES THE BASIN...CENTERED
ON AN ANTICYCLONE OVER THE GULF OF HONDURAS AND EXTENDING N
ALONG 88W INTO THE OHIO VALLEY. A SOUTHERN STREAM MID TO UPPER
CYCLONE WAS SHIFTING EAST NORTHEASTWARD ACROSS NRN MEXICO AND
NEW MEXICO...AND IS FORECAST TO WEAKEN AS IT MOVES INTO THE
LOWER MISSISSIPPI THROUGH MONDAY AND FLATTEN THE RIDGE
CONSIDERABLY. TROPICAL MOISTURE FROM THE EPAC IS BEING DRAWN
FROM THE TROPICS N ACROSS MEXICO AND THEN NE ACROSS THE NW HALF
OF THE BASIN IN THE FORM OF HIGH CLOUDS. AT THE SURFACE...AND
WEAK FRONTAL BOUNDARY MEANDERS ALONG THE N GULF COASTS AND
COASTAL WATERS THIS MORNING...FROM NEAR CORPUS CHRISTI HUGGING
THE COAST TO THE MOUTH OF THE MISSISSIPPI RIVER THEN E-SE TO
THE FLORIDA BIG BEND. A WEAK 1019 MB HIGH WAS CENTERED S OF THIS
BOUNDARY OVER THE NE GULF OF MEXICO NEAR 27N86.5W. AREAS OF
DENSE FOG AND LOW STRATUS COULD BE SEEN IN SATELLITE IMAGERY
EARLIER THIS MORNING N OF THE FRONT SHIFTING SLOWLY S ACROSS THE
COASTAL WATERS FROM SE LOUISIANA TO THE BIG BEND AREA...AND ALSO
ACROSS N FLORIDA. VSBYS HAVE BEGUN TO IMPROVE LATE THIS MORNING
AS FOG AND STRATUS BEGIN TO BURN OFF. A COASTAL TROUGH WAS
EVIDENT ACROSS SW PORTIONS OF THE BASIN ALONG THE MEXICAN COAST
FROM NEAR LA PESCA TO COATZACOALCOS. LIGHT TO MODERATE SOUTHERLY
RETURN FLOW PREVAILED ACROSS NW PORTIONS...AND WAS OVERRUNNING
THE FRONT TO PROVIDE MOISTURE FOR WIDESPREAD CONVECTION ACROSS
MOST OF THE TEXAS COASTAL ZONES AND INTO SW LOUISIANA. THE FRONT
IS EXPECTED TO MEANDER ACROSS THE N AND NW COASTAL WATERS
TODAY...AND REMAIN WEAK ACROSS NE PORTIONS...THEN SHIFT SE
ACROSS W PORTIONS TONIGHT AND SUNDAY...REACHING FROM SE
LOUISIANA TO TAMPICO MEXICO BY SUNDAY AFTERNOON. ACTIVE
CONVECTION IS EXPECTED ALONG THE BOUNDARY TONIGHT AND SUNDAY.

CARIBBEAN SEA...
VERY STABLE ATMOSPHERIC CONDITIONS PERSIST ACROSS THE BASIN
TODAY AS A TUTT AXIS CONTINUES FROM THE CENTRAL ATLC W-SW TO
CENTRAL AMERICA ALONG 10N. THE ATLANTIC RIDGE REMAINS FAR
REMOVED FROM THE BASIN...WHICH IS ALLOWING FOR ONLY LIGHT TO
MODERATE TRADEWINDS ACROSS MOST OF THE BASIN...WHILE TYPICALLY
STRONG TRADES ACROSS S CENTRAL PORTIONS OFFSHORE OF COLOMBIA
WERE ONLY 20 KT THIS MORNING...PER RECENT SCATTEROMETER DATA.
SCATTEROMETER DATA ALSO SHOWED ELY WINDS 15-20 KT ACROSS THE
OUTER WATERS OF THE GULF OF HONDURAS. SMALL CLUSTERS OF BROKEN
MULTI LAYERED CLOUDS AND EMBEDDED MODERATE SHOWERS WERE NOTED
JUST SW OF HISPANIOLA...BETWEEN JAMAICA AND CUBA...AND ACROSS SE
PORTIONS. EXPECT LITTLE CHANGE IN THESE OVERALL CONDITIONS
DURING THE NEXT 24-36 HOURS.

...HISPANIOLA...
THE SANTO DOMINGO UPPER AIR SOUNDING FROM THIS MORNING VERIFIES
SATELLITE IMAGERY...WHERE VERY STABLE MID TO UPPER CONDITIONS
PREVAIL DUE TO SUBSIDENCE ACROSS THE REGION. LIGHT TO MODERATE
TRADES WERE OCCURRING SURROUNDING THE ISLAND...WITH A WEAK WAVE
AGAIN DEVELOPING TO THE LEE OF THE ISLAND OVERNIGHT...YIELDING
THE CLOUDS AND SHOWERS EXTENDING FROM THE BARAHONA PENINSULA W
AND SW TO 16N74.5W. SCATTERED TO BROKEN CUMULUS COULD BE SEEN
DEVELOPING ACROSS THE INTERIOR OF THE ISLAND SINCE 1500
UTC...AND SHOULD DEVELOP SCATTERED SHALLOW CONVECTION DURING THE
AFTERNOON HOURS...THEN CLEAR UP OVERNIGHT. EXPECT SIMILAR
CONDITIONS OVER THE NEXT 24 HOURS AND THIS DIURNAL CYCLE
REPEATS.

ATLANTIC OCEAN...
TUTT AXIS PREVAILS THROUGH THE MIDDLE LEVELS EXTENDING FROM
BROAD  UPPER CYCLONE EXTENDING FROM FRANCE AND PORTUGAL SW TO E
OF THE LESSER ANTILLES THEN WWD ALONG ABOUT 13N INTO THE
CARIBBEAN. A SOUTHERN REGION SHORT WAVE WAS AMPLIFYING ALONG 56-
57W...WITH TROUGH TRAILING OFF THE SW AND REINFORCING SUBSIDENCE
ACROSS THE E AND SE CARIBBEAN. THIS TROUGH SUPPORTS A STATIONARY
FRONT MEANDERS FROM 31N46W TO 23N60W THEN FORMS A WARM FRONT NW
TO NEAR 31N67W. THIS WARM FRONT INTERSECTS A WEAK COLD FRONT
MOVING SLOWLY SE INTO NW PORTIONS NEAR 31N68W TO 29N74W THEN
STATIONARY TO JUST N OF JACKSONVILLE. A PRE FRONTAL TROUGH WAS S
OF THE FRONT TO THE NW BAHAMAS. AREAS OF DENSE FOG HUGGED
FLORIDA E COASTAL ZONES AND COASTAL WATERS THIS MORNING FROM
JACKSONVILLE TO LAKE WORTH BUT HAS SINCE BURNED OFF. ELSEWHERE
THE ATLC RIDGE EXTENDED FROM THE NE ATLC SW INTO CENTRAL
PORTIONS AND WAS PROMOTING MODERATE TRADEWINDS ACROSS THE BASIN
E OF 55W...AS WELL AS N OF THE STALLED FRONT BETWEEN 50W AND
70W. LOOK FOR THE FRONT ACROSS NW PORTIONS TO MOVE E TODAY AND
REACH FROM NEAR BERMUDA TO 29N68W TO OFFSHORE OF JACKSONVILLE BY
THIS EVENING...THEN SINK SLOWLY SE ACROSS CENTRAL PORTIONS
TONIGHT. MEANWHILE...WEAK LOW PRES IS FORECAST TO DEVELOP ACROSS
THE N FLORIDA AND GEORGIA COASTAL WATERS TONIGHT AND SUN AND
REMAIN NEARLY STATIONARY AND WILL CONTINUE TO CONTRIBUTE TO
WEAKENED TRADEWIND FLOW ACROSS MOST OF THE AREA W OF 55W. A WARM
FRONT MAY EVOLVE WITH THE LOW...AND SUFFICIENT PRESSURE GRADIENT
IS EXPECTED N OF THE FRONT TO PRODUCE NE TO E WINDS 20-25 KT
ACROSS EXTREME NW PORTIONS...WHERE CONVECTION WILL BECOME
ACTIVE.

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

$$
STRIPLING


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