Tropical Weather Discussion
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000
AXNT20 KNHC 271801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED MAY 27 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.

...TROPICAL WAVES...

A TROPICAL WAVE IS ANALYZED JUST W OF THE ITCZ FROM THE EQUATOR
TO 13N WITH AXIS ALONG 50W/51W...MOVING AT 13 KT. SSMI TPW
IMAGERY SHOW THE WAVE CONTINUES TO BE EMBEDDED WITHIN ABUNDANT
MOISTURE IN THE MIDDLE TO LOWER LEVELS. SATELLITE DERIVED WINDS
AND MODEL GUIDANCE SHOW A DIFFLUENT ENVIRONMENT ALOFT THAT
SUPPORT SCATTERED MODERATE CONVECTION WITHIN 180-240 NM W OF THE
WAVE AXIS FROM 07N TO 10N. STRONG AT HIGH LEVELS OF THE
ATMOSPHERE ARE PREVENTING THE CONVECTION FROM PERSISTING ONCE IT
FORMS. THE WAVE IS FORECAST TO MOVE INLAND S AMERICA IN ABOUT
36-48 HRS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS OFF THE AFRICAN COAST NEAR
07N13W...AND CONTINUES TO 05N20W. THE ITCZ BEGINS AT 05N20W...
AND CONTINUES TO 05N30W AND TO JUST E OF THE TROPICAL WAVE ALONG
50W/51W. SCATTERED MODERATE CONVECTION IS WITHIN 60-120 NM S OF
THE TROUGH BETWEEN 10W-20W. FOR CONVECTION ASSOCIATED WITH THE
TROPICAL WAVE SEE THE SECTION ABOVE.

...DISCUSSION...

GULF OF MEXICO...

A SHARP UPPER TROUGH AXIS EXTENDS FROM WESTERN ALABAMA S TO
25N87W AND TO THE FAR NW CARIBBEAN SEA. AN ASSOCIATED UPPER
LEVEL DISTURBANCE IS MOVING ACROSS SOUTHERN LOUISIANA AS VERY
DEEP MOIST SOUTHERLY FLOW OF 15 KT AROUND THE SOUTHERN PERIPHERY
OF A WESTERN ATLANTIC RIDGE THAT STRETCHES FROM THE WESTERN
ATLANTIC SW TO THE NE GULF REMAINS IN PLACE. EARLIER DEEP
CONVECTION OF SCATTERED MODERATE/ISOLATED STRONG TYPE INTENSITY
THAT FIRED UP OVER EASTERN TEXAS EARLY THIS MORNING HAS PUSHED
SEWD INTO THE FAR N CENTRAL WATERS S AND SW OF LOUISIANA. AS OF
15Z...IT IS ANALYZED AS A FAST MOVING SQUALL LINE THAT EXTENDS
FROM S CENTRAL LOUISIANA SW TO 28N94W. THE CONVECTION EXTENDS
WITHIN ABOUT 30 NM OF THIS LINE. BROAD UPPER RIDGING IS SLIDING
EASTWARD BEHIND THE UPPER TROUGH. WATER VAPOR IMAGERY SHOWS
MODERATE SUBSIDENCE WITH RATHER STABLE ATMOSPHERIC CONDITIONS S
OF 27N AND W OF 90W. SCATTERED TO LOCALLY BROKEN LOW CLOUDS WITH
ISOLATED SHOWERS MOVING QUICKLY WNW IN THE MOIST SE FLOW ARE
SEEN S OF 26N E OF 88W...WHILE SCATTERED SHOWERS AND ISOLATED
TSTMS ARE UNDERNEATH THE UPPER TROUGH AXIS FROM 23N-26N BETWEEN
88W-90W. THE TYPICAL NOCTURNAL TROUGH MOVED OFF THE YUCATAN
PENINSULA THIS MORNING...AND IS OVER THE EASTERN PART OF THE SW
GULF. IT HAS NO CONVECTION WITH IT AS IT IS UNDER THE DRY AND
SUBSIDENT AIR ALOFT. HAZE APPEARS TO BE THINNING OUT OVER THE NW
GULF. THE UPPER TROUGH WILL REACH THE EASTERN GULF THU...THEN
WEAKEN ON FRI AS SURFACE RIDGING CHANGES LITTLE OVER THE NE AND
CENTRAL GULF PORTIONS.

CARIBBEAN SEA...

BROAD UPPER TROUGHING EXTENDS FROM THE CENTRAL ATLANTIC SW TO
THE SW CARIBBEAN. THE UPPER FLOW IS NW BEHIND THE TROUGH.
MODERATE SUBSIDENCE ALOFT WITH STABLE ATMOSPHERIC CONDITIONS AND
GENERALLY FAIR WEATHER CONDITIONS ARE SEEN OVER MUCH OF THE
CARIBBEAN BASIN...WITH THE EXCEPTION OF THE FAR NW PORTION WHERE
THE LOW-LEVEL ELY FLOW IS QUITE MOIST AND UNSTABLE AHEAD OF THE
AFOREMENTIONED GULF OF MEXICO UPPER TROUGH. SCATTERED SHOWERS
AND ISOLATED TSTMS ARE SEEN N OF 18N BETWEEN 79W-85W. A PATCH OF
LOW-LEVEL MOISTURE WITH ISOLATED SHOWERS MOVING WESTWARD IS FROM
16N-19N BETWEEN SW HAITI TO JUST E OF JAMAICA. VERY SHALLOW
MOISTURE OVER THE NE CARIBBEAN SUPPORTS ISOLATED SHOWERS N OF
15N E OF 68W. NWS DOPPLER RADAR FROM SAN JUAN AND SATELLITE
IMAGERY ARE SHOWING SCATTERED SHOWERS AND TSTMS DEVELOPING OVER
THE INTERIOR OF PUERTO RICO WITH DAYTIME HEATING...AND WITH THE
APPROACH OF A WEAK LOW-LEVEL INSTABILITY BOUNDARY APPROACHING
FROM THE N. A STRONG UPPER JET E OF THE UPPER TROUGH IS PRESENT
ACROSS THE FAR SOUTHERN CARIBBEAN. IT IS ADVECTING THIN UPPER
MOISTURE EASTWARD S OF 14N AND E OF NW COLOMBIA.

THE COMBINATION BETWEEN HIGH PRESSURE ACROSS THE ATLANTIC AND
BROAD LOW PRESSURE OVER COLOMBIA AND THE SW CARIBBEAN IS
RESULTING IN A TIGHT PRESSURE GRADIENT IN THE SW CARIBBEAN
PRODUCING NE-E WINDS OF 20-25 KT FROM 11N-14N BETWEEN 72W-77W
WITH SEAS THERE UP TO 9 FT. ELSEWHERE...TRADE WINDS OF 15-20 KT
ARE PRESENT WITH SEAS LESS THAN 8 FT ARE PRESENT. OVERALL...NO
SIGNIFICANT CHANGES ARE EXPECTED OVER THE NEXT COUPLE OF DAYS.

...HISPANIOLA...

STRONG SUBSIDENCE ALOFT IS BRINGING MOSTLY DEEP LAYER DRY AIR
ACROSS JUST ABOUT THE ENTIRE ISLAND...EXCEPT OVER THE EXTREME SW
PORTION WHERE SHALLOW LAYER MOISTURE...AND UPPER LEVEL TROUGHING
IN THE VICINITY SUPPORTS PATCHES OF LOW-LEVEL MOISTURE WITH
ISOLATED SHOWERS OVER THE SW PORTION...AND WSW FROM THERE TO
JUST E OF JAMAICA. SCATTERED TO LOCALLY BROKEN LOW CLOUDS WITH
ISOLATED SHOWERS AND TSTMS ARE JUST BEGINNING TO DEVELOP OVER
THE MAINLY THE HIGHER TERRAIN AREAS. THIS ACTIVITY MAY REACH
MORE OF THE SCATTERED LIMITS LATER IN THE AFTERNOON...AND AGAIN
ON THU AS THE INFLUENCING SYNOPTIC PATTERN CHANGES LITTLE.
PRECIPITABLE WATER GUIDANCE SUGGESTS THAT MOISTURE CONTENT
INCREASES THU AND FRI FOR MUCH OF HISPANIOLA AND VICINITY WATERS.

ATLANTIC OCEAN...

A NEARLY STATIONARY MID/UPPER LEVEL LOW ANCHORED NEAR 26N61W
CONTINUES TO SUPPORT A SURFACE TROUGH WITH AXIS EXTENDING FROM
32N62W TO 28N63W...AND TO 22N59W. SATELLITE IMAGERY DEPICTS
NUMEROUS SHOWERS AND SCATTERED TSTMS FROM 24N-30N BETWEEN 51W-
58W. SCATTERED SHOWERS AND TSTMS ROTATING CYCLONICALLY ARE NOTED
FROM 24N-30N BETWEEN 58W-63W. A TROPICAL WAVE IS W OF THE ITCZ
AS DESCRIBED UNDER TROPICAL WAVES SECTION ABOVE. WATER VAPOR
IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE PREVAILING W OF THE
MID/UPPER LOW AND SURFACE KEEPING MOSTLY TRANQUIL WEATHER
THERE...WITH THE EXCEPTION OF THE WATERS BETWEEN THE BAHAMA
ISLAND CHAIN AND THE GREATER ANTILLES WHERE LOW-LEVEL MOISTURE
LEFT OVER FROM A PREVIOUS INSTABILITY LINE IS ADVECTING WSW
TOWARDS THOSE AREAS. THE SSMI TPW IMAGERY PICKS UP ON THIS LOW
-LEVEL MOISTURE WHICH IS ATTENDANT BY WIDELY SCATTERED SHOWERS.
ELSEWHERE SURFACE HIGH PRESSURE AND FAIR WEATHER PREVAILS. THE
SURFACE TROUGH WILL CONTINUE TO DRIFT WESTWARD DURING THE NEXT
48 HOURS WITH POSSIBLE WEAK LOW PRESSURE ALONG IT. STRONG HIGH
PRESSURE RIDGING IS OBSERVED E OF THE TROUGH ACROSS THE EASTERN
PART OF THE DOMAIN.

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

$$
AGUIRRE



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