000
AXPZ20 KNHC 132217
TWDEP 

TROPICAL WEATHER DISCUSSION      
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN MAY 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 09N77W TO 08N93W TO LOW PRES AT 
09.5N104.5W 1009 MB TO LOW PRES AT 07.5N118W 1010 MB TO 06N120W 
THEN TRANSITIONS TO ITCZ CONTINUING ON TO 02N140W. SCATTERED TO  
NUMEROUS MODERATE TO STRONG CONVECTION S OF TROUGH TO 03N E OF 
95W. SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120 NM N OF 
TROUGH FROM 89W TO 94W. SCATTERED MODERATE TO STRONG CONVECTION 
WITHIN 120 NM N OF ITCZ FROM 126W TO 134W. SCATTERED MODERATE TO 
STRONG WITHIN 90 NM OF LOW PRES CENTER AT 09.5N104.5W EXCEPT 310 
NM NE QUADRANT. 

...DISCUSSION...
ALOFT...WELL-DEFINED DEEP LAYER CYCLONE AT 36N128W MOVING NE 
AWAY FROM FORECAST AREA AND IS DRAGGING A MIDDLE TO UPPER LEVEL 
TROUGH SW TO 22N140W.  VERY DRY SUBSIDING AIR MASS W OF TROUGH 
AXIS. SHARP HIGH AMPLITUDE RIDGE IS SQUEEZED ALONG 117W N OF 
AREA...BETWEEN CYCLONE AND DEVELOPING CYCLONE OVER DESERT SW OF 
THE U.S. SOUTH OF THESE FEATURES A BROAD RIDGE IS CENTERED ALONG 
120W. WEAK MIDDLE LEVEL CYCLONIC TURNING NOTED IN WATER VAPOR 
IMAGERY SHIFTING W OFF W COAST OF MEXICO AND S OF THE BAJA 
PENINSULA. CONVERGENCE AND SUBSIDENCE WITHIN THIS TROUGHING 
PRODUCING VERY DRY STABLE CONDITIONS AND HELPS TO EXPLAIN NEARLY 
CLOUD FREE SKIES ACROSS MUCH OF THE AREA E OF 123W N OF THE 
MONSOON TROUGH. VERY SHALLOW MOISTURE IN THE MARINE LAYER 
PRODUCING STRATOCUMULUS W OF THE BAJA PENINSULA UNDERNEATH THIS 
SUBSIDENCE. A SECOND TROPICAL RIDGE HAS SHIFTED EWD PAST 24-48 
HOURS...NOW CENTERED ON UPPER ANTICYCLONE NEAR 15N91W EXTENDING 
N-NE ACROSS GULF OF MEXICO. SCATTERED DEEP CONVECTION CONTINUES 
TO PULSE AND FLARE ON BOTH SIDES OF THE MONSOON TROUGH AND 
UNDERNEATH THIS UPPER RIDGE...WITH LIGHT ANTICYCLONIC SHEAR 
ALLOWING FOR DEEP CONVECTIVE GROWTH. 

...AT LOWER LEVELS...TWO LOW PRES CENTERS EMBEDDED IN THE 
MONSOON TROUGH DESCRIBED ABOVE HAVE BEEN INDUCING SCATTERED TO 
MODERATE DEEP CONVECTION ENHANCED BY WARM SST AND FAVORABLE 
UPPER LEVEL SUPPORT TODAY...BUT CONVECTION ASSOCIATED WITH THE 
WESTERN-MOST LOW ALONG 118W HAS DIMINISHED SIGNIFICANTLY IN THE 
PAST FEW HOURS. SOME OF THE GLOBAL MODELS HAVE BEEN QUITE 
BULLISH IN INTENSIFYING THE EASTERN-MOST LOW ALONG 104.5W IN 
RECENT DAYS...BUT HAVE SINCE MODERATED THEIR INTENSIFICATION. 
THIS LOW DOES HOWEVER APPEAR BETTER ORGANIZED THAN 24 HOURS AGO 
AND HAS A MODERATE POTENTIAL TO INTENSIFY INTO A TROPICAL 
CYCLONE IN THE NEXT 48 HOURS. DRY LOW AND MID LEVEL AIR LIES TO 
THE NW OF THIS SYSTEM AND COMBINED WITH A MODEST INCREASE IN 
WIND SHEAR MAY BE THE DETERMINING FACTOR IN IT NOT BECOMING 
BETTER ORGANIZED. 

...ELSEWHERE AT THE LOWER LEVELS...
1021 MB HIGH PRES CENTER NEAR 29N127W HAS SHIFTED SUFFICIENTLY E 
PAST 24 HOURS TO INDUCE MODEST PRES GRADIENT ALONG THE W COAST 
OF BAJA CALIFORNIA...BRINGING A FRESH NW BREEZE ALONG CALIFORNIA 
W COAST EXTENDING S ALONG BAJA PENINSULA N OF 28N. THIS AREA OF 
FRESH WINDS WILL EXPAND S TO 24N BY 48 HOURS.

WEAK TROUGH OVER BAY OF CAMPECHE HAS FORCED N WINDS ACROSS 
CHIVELA PASS AND THROUGH THE GULF OF TEHUANTEPEC YIELDING NARROW 
PLUME OF 20-25 KT WINDS. WINDS ARE EXPECTED TO REACH 20 TO 30 KT 
TONIGHT AND MON BEFORE DIMINISHING LATE TUE. 

FRESH E WINDS OVER GULF OF PAPAGAYO EXPECTED TO DIMINISH MON AS 
WEAK LOW PRES S OF GULF DRIFTS W.

LARGE CONVECTIVE OUTBREAK THIS AFTERNOON OVER THE FAR EPAC OFF W 
COAST OF COLOMBIA MAY VERY WELL HAVE BEEN INITIATED BY VERY WEAK 
EARLY SEASON TROPICAL WAVE. EASTERLY PERTURBATIONS THUS FAR THIS 
YEAR HAVE REMAINED LOW LATITUDE...BUT LIKELY THAT A FEW HAVE 
ALREADY TRAVERSED W ACROSS SOUTHERN FRIDGES OF THE BASIN.

$$

STRIPLING