000
AXPZ20 KNHC 202113 CCA
TWDEP 

TROPICAL WEATHER DISCUSSION...CORRECTED  
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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.

CORRECTED TC PROBABILITY OF SPECIAL FEATURE

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...SPECIAL FEATURE...
1006 MB LOW PRES CENTER NEAR 09N99W REMAINS EMBEDDED IN THE 
MONSOON TROUGH. SATELLITE IMAGERY SHOWING ORGANIZED LOW LEVEL 
CLOUD LINES COILING INTO APPARENT MID LEVEL CYCLONIC CIRCULATION.
SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 120 NM OF THE 
ESTIMATED CENTER. NUMERICAL MODEL GUIDANCE SUGGESTS THE LOW WILL 
REMAIN NEARLY STATIONARY WHILE THIS SYSTEM STEADILY DEVELOPS OVER
THE NEXT SEVERAL DAYS AS ENVIRONMENTAL CONDITIONS IMPROVE. THERE 
IS A HIGH...60 PERCENT...CHANCE OF THIS LOW DEVELOPING INTO A 
TROPICAL CYCLONE WITHIN THE NEXT 24-48 HOURS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM 09N84W TO 11N93W TO A LOW PRES 
NEAR 09N99W 1006 MB TO 07N120W. THE ITCZ AXIS EXTENDS FROM 
07N120W TO BEYOND 04N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS WITHIN 150 NM EITHER SIDE OF TROUGH AXIS E OF 95W.

...DISCUSSION...
AN ACTIVE MONSOON TROUGH PERSISTS E OF 103W. A BROAD UPPER LEVEL 
ANTICYCLONE CENTERED OVER GUATEMALA EXTENDS A UPPER RIDGE OVER 
THE SURFACE TROUGH FROM 65W TO 112W. DIVERGENT FLOW ALOFT AND 
LIGHT ANTICYCLONIC WIND SHEAR S OF THE RIDGE IS MAINTAINING A 
VERY FAVORABLE ENVIRONMENT FOR DEEP CONVECTION. ABUNDANT TROPICAL
MOISTURE. IS POOLED S OF THE MONSOON TROUGH E OF 105W. SCATTERED 
MODERATE TO STRONG CONVECTION CONTINUES TO PULSE IN CLUSTERS 
ACROSS THIS VERY UNSTABLE REGION...FURTHER ENHANCING DIVERGENCE 
ALOFT...AND AIDING IN THE MAINTENANCE OF THE UPPER LEVEL RIDGE.

FRESH TO STRONG N-NE WINDS ARE FUNNELING THROUGH AND DOWNSTREAM 
OF ISTHMUS OF TEHUANTEPEC FROM THE PRES GRADIENT BETWEEN RIDGING 
IN THE WESTERN GULF OF MEXICO AND A TROUGH OVER THE E COAST OF 
THE YUCATAN PENINSULA. HIGH PRES OVER THE NORTHERN GULF OF 
MEXICO WILL RETROGRADE WEST THEN WEAKEN AS IT SINKS SOUTHWARD 
MON. THE PRES GRADIENT WILL REMAIN STRONG BETWEEN THIS RIDGE AND 
THE DEEPENING LOW PRES SYSTEM CURRENTLY NEAR 09N99W. THIS WILL 
ALLOW E-NE WINDS TO REMAIN FRESH TO STRONG DOWNSTREAM FROM THE 
GULF OF TEHUANTEPEC TO AROUND 102W THROUGH EARLY TUE.

A RELATIVELY WEAK 1022 MB SUBTROPICAL HIGH NEAR 30N136W EXTENDS 
A WEAK RIDGE ACROSS THE NORTHERN PORTION OF THE FORECAST AREA. A 
COLD FRONT APPROACHING FROM THE NW WILL FORCE THE HIGH SW TO 
NEAR 30N140W WHERE IT WILL GRADUALLY STRENGTHEN THROUGH EARLY 
TUE. THE ASSOCIATED PRES GRADIENT ON THE E SIDE OF THE HIGH WILL 
SUPPORT MODERATE TO FRESH N-NW WINDS W OF THE BAJA PENINSULA 
OVER NE WATERS TONIGHT. THE PRES GRADIENT WILL TIGHTEN TUE AND 
EXPAND THE AREA OF FRESH WINDS SOUTHWESTWARD AND BUILD SEAS TO 
AROUND 8 FT IN WESTERN PORTION OF THE DISCUSSION AREA. 

REMNANT LOW OF TROPICAL DEPRESSION ALETTA IS NEAR 12N112W SINKING
SLOWLY S AND TRANSITIONING INTO AN ELONGATED TROUGH THAT EXTENDS 
WESTWARD TO AROUND 119W...WITH ONLY A SWIRL OF LOW LEVEL CLOUDS.

$$
MUNDELL