000
AXPZ20 KNHC 200909
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN MAY 20 2012

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 
0730 UTC.

...SPECIAL FEATURES...

1006 MB LOW PRES NEAR 11N98W IS CURRENTLY EMBEDDED IN THE 
MONSOON TROUGH. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION IS SKEWED BETWEEN 120 NM AND 330 NM IN THE SW 
SEMICIRCLE OF THE LOW EXCEPT TO 510 NM IN THE SW QUADRANT. BOTH 
THE 0424 UTC ASCAT AND 0550 UTC OSCAT PASSES SAW 20 KT WINDS S 
OF THE LOW AND THE 0300 UTC JASON1 PASS NOTED SEAS TO 8 FT. 
NUMERICAL MODEL GUIDANCE SUGGESTS SOME SLOW DEVELOPMENT OF THIS 
SYSTEM OVER THE NEXT SEVERAL DAYS. THERE IS A MODERATE CHANCE OF 
THIS LOW DEVELOPING INTO A TROPICAL CYCLONE IN THE NEXT 48 HOURS.

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

THE MONSOON TROUGH AXIS WAS ANALYZED FROM 14N92W TO LOW PRES 
NEAR 11N98W 1006 MB TO 06N126W. THE ITCZ AXIS WAS ANALYZED FROM 
06N126W TO 04N140W. ASIDE FROM THE CONVECTION NOTED WITH THE LOW 
PRES SYSTEM DESCRIBED IN THE SPECIAL FEATURES SECTION... 
SCATTERED MODERATE CONVECTION LIES WITHIN 150 NM EITHER SIDE OF 
THE MONSOON TROUGH AXIS ALONG THE COAST OF SOUTHERN MEXICO AND 
GUATEMALA. 

...DISCUSSION...

A RIDGE ALOFT CENTERED FROM EASTERN HONDURAS TO ACAPULCO MEXICO 
THEN SOUTHWESTWARD TO 10N120W IS CREATING BROAD UPPER DIFFLUENCE 
OVER THE COAST NEAR THE MONSOON TROUGH AND IN THE VICINITY OF 
THE SURFACE LOW MENTIONED IN THE SPECIAL FEATURES SECTION. 
PRECIPITABLE WATER VALUES ARE IN THE 2.0-2.5 INCH RANGE S OF 
THE RIDGE AXIS. THE VERTICAL LIFT OF THIS MOISTURE IS ENHANCING 
THE AFOREMENTIONED CONVECTION...AND THE AREA OF POOLED MOSITURE 
ALSO ENCOMPASSES A REGION OF SCATTERED MODERATE WITH ISOLATED 
STRONG CONVECTION FROM 02N TO 12N BETWEEN 82W AND 93W. THIS 
CONVECTION IS BEING ENHANCED BY THE UPPER LEVEL DIFFLUENCE 
GENERATED BY THE REAR RIGHT QUADRANT OF A 35 KT NORTHEASTERLY 
UPPER JET CENTERED FROM 06N90W SOUTH OF THE EQUATOR TO 04S102W.

A FRESH TO STRONG BREEZE THROUGH ISTHMUS OF TEHUANTEPEC WILL BE 
FORCED BY THE PRES GRADIENT BETWEEN RIDGING IN THE WESTERN GULF 
OF MEXICO AND STATIONARY TROUGHING OVER THE E COAST OF THE 
YUCATAN PENINSULA BEGINNING LATER THIS MORNING. HIGH PRES OVER 
THE U.S. GULF COAST STATES WILL RETROGRADE WESTWARD TODAY AND 
WEAKEN AS IT SINKS SOUTHWARD INTO THE NW GULF TOMORROW. THE PRES 
GRADIENT WILL REMAIN STRONG BETWEEN THIS RIDGING AND THE 
LOWERING PRESSURES TO THE SOUTH ASSOCIATED WITH THE LOW PRES 
SYSTEM DISCUSSED IN THE SPECIAL FEATURES SECTION. THIS WILL 
ALLOW WINDS TO REMAIN FRESH TO STRONG HERE THROUGH AT LEAST 
EARLY TUE.

THE RELATIVELY WEAK 1022 MB SUBTROPICAL HIGH NEAR 33N130W 
EXTENDS A RIDGE ACROSS THE FAR NW CORNER OF THE FORECAST AREA TO 
JUST N OF THE HAWAIIAN ISLANDS. A COLD FRONT ENCROACHING ON THE 
HIGH FROM THE NW WILL FORCE IT SOUTHWESTWARD TO 30N140W TODAY 
WHERE IT WILL GRADUALLY STRENGTHEN THROUGH EARLY TUE. THE PRES 
GRADIENT IS STRONG ENOUGH ON THE E SIDE OF THE HIGH TO 
GENERATE A MODERATE TO FRESH N BREEZE WELL OFF THE BAJA 
PENINSULA OVER NE WATERS THAT WILL PERSIST THROUGH EARLY MON. AS 
THE HIGH BUILDS MON...THE PRES GRADIENT BETWEEN IT AND THE ITCZ 
WILL STRENGTHEN AND THE AREA OF FRESH WINDS WILL EXPAND 
SOUTHWESTWARD FROM NE WATERS TO ENCOMPASS THE USUAL TRADE WINDS 
REGION OVER W CENTRAL WATERS.

THE REMNANTS OF FORMER TROPICAL CYCLONE ALETTA CURRENTLY LIE 
NEAR 13N112W. THE CENTER OF THIS 1010 MB LOW PRES SYSTEM IS 
BEGINNING TO BECOME ELONGATED AS SUGGESTED BY THE 0428 UTC ASCAT 
PASS. THIS PASS CAPTURED A SMALL AREA OF 20 KT WINDS IN THE W 
QUADRANT OF THE LOW. THE LOW AND THESE WINDS ARE EXPECTED TO 
DIMINISH LATER THIS MORNING. THESE IS NO SIGNIFICANT CONVECTION 
ASSOCIATED WITH THE REMNANTS OF ALETTA.

$$
SCHAUER