000
AXPZ20 KNHC 170241
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
0405 UTC SUN MAY 17 2015

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0100 UTC.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              

THE MONSOON TROUGH AXIS WAS ANALYZED FROM 09N93W TO 07N99W TO 
09N111W TO TO 08N118W TO 09N125W TO 07N132W. THE ITCZ AXIS WAS 
ANALYZED FROM 07N132W TO 08N137W TO 08N140W. SCATTERED MODERATE 
WITH ISOLATED STRONG CONVECTION WAS WITHIN 180 NM-390 NM S OF 
THE AXIS BETWEEN 99W AND 106W. ISOLATED MODERATE TO STRONG 
CONVECTION WAS WITHIN 360 NM S OF THE AXIS BETWEEN 111W-121W. 
SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 
270 NM N OF THE AXIS W OF 135W.
 
...DISCUSSION...

THE SUBTROPICAL RIDGE EXTENDS THROUGH N WATERS FROM 29N140W TO 
27N115W. A COLD FRONT LIES TO THE N OF THIS RIDGE AXIS. THE COLD 
FRONT HAS REACHED THE FORECAST AREA NEAR 32N140W THIS EVENING... 
WILL DIP INTO NW WATERS OVERNIGHT AND WILL STRETCH FROM 32N130W 
TO 29N133W TO 28N140W BY SUN AFTERNOON. THE FRONT IS FORECAST TO 
BE DISSIPATING FROM WEAK 1020 MB LOW PRES NEAR 31N126W TO 
25N131W SUN AFTERNOON. WINDS NEAR THE FRONT ARE EXPECTED TO 
REMAIN BELOW A FRESH BREEZE AND SEAS TO 8 FT SHOULD BE CONFINED 
N OF 30N BEHIND THE FRONT. 1030 MB HIGH PRESSURE CURRENTLY LIES 
BEHIND THE FRONT NEAR 38N150W. THE HIGH IS FORECAST TO WEAKEN AS 
IT SHIFTS SE WITH THE FRONT. THIS SHOULD KEEP THE PRESSURE 
GRADIENT RELATIVELY CONSTANT AND MAINTAIN THE AREA OF FRESH 
TRADES FOUND W OF 120W.

MEAN TROUGHING ALOFT OVER NW MEXICO AND THE SW UNITED STATES 
WILL CONTINUE THROUGH THE PERIOD. AN UPPER LOW OVER NW WYOMING 
WILL CARRY ITS TROUGH AXIS E OUT OF NW MEXICO TONIGHT. THE 
ASSOCIATED COLD FRONT AT THE SURFACE HAS WEAKENED RAPIDLY OVER 
THE FORECAST AREA AND ONLY A SMALL PORTION REMAINS FROM JUST S 
OF JUAREZ MEXICO TO THE SIERRA MADRE NEAR 30N110W. SEAS OFFSHORE 
HAVE SUBSIDED BELOW 8 FT. THE NEXT SHORTWAVE UPPER TROUGH IS 
DROPPING INTO THE BACKSIDE OF THE MEAN TROUGH AND WILL HELP CUT 
OFF AN UPPER LOW OFF THE CENTRAL CALIFORNIA COAST BY SUN NIGHT 
BEFORE MOVING INTO CALIFORNIA...BUT THE COLD FRONT AT THE 
SURFACE EXPECTED TO DISSIPATE WELL OFFSHORE BY SUN AFTERNOON AS 
DESCRIBED IN THE PREVIOUS PARAGRAPH. 

A VAST ANTICYCLONE ALOFT CENTERED NEAR 11N115W EXTENDS ITS 
PRIMARY RIDGE AXIS W TO 11N140W AND ANOTHER RIDGE AXIS TO THE 
EQUATOR NEAR 117W. CONVECTION UNDER THIS ANTICYCLONE IS 
DESCRIBED IN THE SECTION ABOVE. THE BULK OF THE DEEP CONVECTION 
IN THE PORTION OF THE AREA W OF 110W CAN BE FOUND UNDER THE 
UPPER LEVEL DIVERGENCE ASSOCIATED WITH THESE RIDGE AXES WHICH IS 
ENHANCING LIFT IN THE ATMOSPHERE IN AREAS OF PLENTIFUL LOW- AND 
MID-LEVEL MOISTURE. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION IN THE SE PORTION OF THE AREA IS OVER COSTA RICA AND 
WITHIN 60 NM OF ITS COAST. THIS AREA LIES IN THE REAR RIGHT 
QUADRANT OF A SOUTHWESTERLY JET THAT EXTENDS INTO THE CARIBBEAN. 
THE JET AXIS IS FORECAST TO SHIFT N OVER THE NEXT TWO DAYS...AND 
THE FORECAST CALLS FOR THE CHANCE OF PRECIPITATION TO INCREASE 
OVER NICARAGUA AS A RESULT.
 
GAP WINDS...                                                     
GULF OF PAPAGAYO...THE PRESSURE GRADIENT BETWEEN RIDGING OVER 
THE NW CARIBBEAN AND TROUGHING TO THE SW WILL SUPPORT A FRESH TO 
STRONG BREEZE IN THE GULF OF PAPAGAYO TO 89W BY THE EARLY 
MORNING HOURS SUN WITH THE ASSISTANCE OF NOCTURNAL DRAINAGE 
FLOW. THESE WINDS WILL DIMINISH AFTER SUNRISE AND RETURN AGAIN 
EARLY MON MORNING ONLY TO DIMINISH AGAIN AFTER SUNRISE MON. 
 
$$
SCHAUER