000
AXPZ20 KNHC 300923
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1005 UTC THU MAY 30 2013

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...SPECIAL FEATURE...

BARBARA CONTINUES TO QUICKLY WEAKEN WHILE MOVING FURTHER INLAND 
OVER THE ISTHMUS OF TEHUANTEPEC. HEAVY RAIN CONTINUES ACROSS 
PORTIONS OF SOUTHEASTERN MEXICO IN ASSOCIATION WITH THIS 
TROPICAL CYCLONE. ARRIAGA IN THE STATE OF CHIAPAS RECENTLY 
REPORTED A RAINFALL TOTAL OF 16.02 INCHES...407 MM...IN THE LAST 
18 HOURS WHILE AN AUTOMATIC STATION NEAR TONALA REPORTED MAXIMUM 
SUSTAINED WINDS OF 70 KT...130 KM/H. BARBARA WAS DOWNGRADED TO A 
TROPICAL DEPRESSION AT 0900 UTC. AT THIS TIME...IT IS CENTERED 
NEAR 17.8N 93.9W MOVING N AT 7 KT. ON THE FORECAST TRACK...THE 
CENTER OF BARBARA IS EXPECTED TO EMERGE OVER THE EXTREME 
SOUTHWESTERN GULF OF MEXICO LATER TODAY. MINIMUM CENTRAL 
PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WINDS ARE 30 KT GUSTS 40 
KT. BARBARA IS FORECAST TO WEAKEN TO A REMNANT LOW LATER TODAY.  
SEE THE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP2/WTPZ22 KNHC...OR THE LATEST PUBLIC ADVISORY UNDER 
AWIPS/WMO HEADERS MIATCPEP2/WTPZ32 KNHC...FOR MORE DETAILS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

MONSOON TROUGH EXTENDS FROM 09N84W TO 08N91W THEN RESUMES AT 
13N112W TO 08N123W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING 
ON TO BEYOND 06N140W. CLUSTERS OF SCATTERED MODERATE TO STRONG 
CONVECTION ARE N OF 09N E OF 88W. SCATTERED MODERATE ISOLATED 
STRONG CONVECTION IS NOTED WITHIN 150 NM S OF TROUGH BETWEEN 85W 
AND 90W.
 
...DISCUSSION...

ALOFT...AN ANTICYCLONE CENTERED JUST W OF AREA NEAR 14N142W 
EXTENDS A RIDGE OVER THE WEST PART OF THE FORECAST REGION... 
PARTICULARLY W OF 128W. A CUT-OFF LOW HAS DEVELOPED E OF THE 
RIDGE AND NOW IS LOCATED NEAR 18N122W. THIS LOW WILL DRIFT WWD 
OVER THE NEXT 24 HOURS. ANOTHER ANTICYCLONE IS CENTERED NEAR 
15N107W WHILE MAINLY NE WIND FLOW ALOFT DOMINATES THE REMAINDER 
OF THE AREA. MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY AIR 
MASS COVERS MOST OF THE AREA N OF 10N W OF 120W AND N OF 18N E 
OF 120W...INCLUDING BAJA CALIFORNIA AND NW MEXICO. SWLY FLOW 
DOMINATES THE FAR NW CORNER WITH A FAIR AMOUNT OF MID/TO UPPER 
LEVEL MOISTURE.
 
MONSOONAL FLOW DOMINATES THE TROPICS E OF 120W...AND IS EXPECTED 
TO PRODUCE VERY MOIST AND UNSTABLE CONDITIONS DURING THE NEXT 
FEW DAYS. A SECOND LOW PRES CENTER REMAINS EMBEDDED WITHIN THE 
MONSOON TROUGH NEAR 13N112W. CONVECTION HAS BEEN FLARING ON AND 
OFF DURING THE PAST DAY OR SO WITH THIS FEATURE...AND CURRENTLY 
ONLY SCATTERED MODERATE CONVECTION IS NOTED WITHIN 60 NM OF 
CENTER. WHILE ENVIRONMENTAL CONDITIONS DO NOT FAVOR SIGNIFICANT 
STRENGTHENING...THERE IS STILL SOME POTENTIAL FOR THIS SYSTEM TO 
BECOME A TROPICAL DEPRESSION TODAY AS IT MOVES NORTHEASTWARD AT 
ABOUT 10 MPH. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A 
TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THE STRONGEST WINDS 
ASSOCIATED WITH THIS SYSTEM ARE TO THE E AND SE OF THE LOW 
CENTER BASED ON THE 0506 UTC HIGH RESOLUTION ASCAT PASS THAT 
SHOWS 20-30 KT WINDS WITHIN 150 NM E SEMICIRCLE...WHILE STRONG 
MONSOONAL SW WINDS OF 20-25 KT PREVAILS TO THE SE. NLY WINDS OF 
20 KT ARE NOTED IN THE NW QUADRANT. 

AT THE SURFACE...A 1026 MB HIGH PRES LOCATED NEAR 32N140W 
EXTENDS A RIDGE SEWD ACROSS THE FORECAST WATERS TO NEAR 20N120W. 
THIS FEATURE IS FORECAST TO MOVE NE AND WILL MERGE WITH ANOTHER 
HIGH CENTER NEAR 38N133W OVER THE NEXT 24 HOURS. THE NEW HIGH IS 
FORECAST TO STRENGTHEN BY SAT BRINGING FRESH TO STRONG WINDS TO 
THE N WATERS MAINLY N OF 27N BETWEEN 121W AND 132W WITH BUILDING 
SEAS OF 8 TO 11 FT. CURRENTLY...A TIGHT PRES GRADIENT BETWEEN 
THE RIDGE AND LOWER PRES OVER NW MEXICO CONTINUES TO RESULT IN 
NW TO N WINDS OF 20-25 KT OVER THE NE PART OF THE FORECAST 
REGION N OF ABOUT 28N BETWEEN 118W AND 122W WITH SEAS THERE IN 
THE 8-10 FT RANGE. 

LONG PERIOD CROSS EQUATORIAL SW SWELLS AT 14-16 SECONDS DOMINATE 
MOST OF THE FORECAST WATERS E OF 115W. THESE SWELLS ARE MERGING 
WITH NW TO N SWELLS THAT COVER THE REMAINDER OF THE FORECAST 
WATERS. ADDITIONAL PULSES OF SW SWELL SHOULD REACH THE SOUTH 
CENTRAL WATERS LATER TODAY.
 
$$ 
GR