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Atlantic Tropical Weather Discussion



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 
WWW.HURRICANES.GOV/MARINE

$$
AGUIRRE


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Page last modified: Wednesday, 27-May-2015 18:02:07 UTC