000
AXPZ20 KNHC 180927
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL 
1005 UTC MON MAR 18 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 
0730 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 09N84W TO 08N88W TO 
03N93W. THE ITCZ AXIS WAS ANALYZED FROM 03N93W TO 01N120W TO 
03N128W TO 02N140W. ISOLATED MODERATE CONVECTION WAS WITHIN 180 
NM N OF THE AXIS BETWEEN 110W AND 120W AS WELL AS WITHIN 180 NM 
N OF THE AXIS W OF 133W.

...DISCUSSION...                                                 
LINGERING E-NE SWELL FROM AN EARLIER GAP WIND EVENT CONTINUES TO 
SUPPORT SEAS TO 8 FT FROM 04N-10N BETWEEN 105W AND 118W. SEAS 
WILL SUBSIDE TO LESS THAN 8 FT HERE BY THIS AFTERNOON. GAP WINDS 
ARE NOT EXPECTED TO RETURN BEFORE THE END OF THE FORECAST PERIOD 
EARLY ON WED MORNING. 
 
A POSITIVELY TILTED UPPER-LEVEL TROUGH EXTENDS ACROSS MEXICO 
FROM THE EASTERN RIO GRANDE VALLEY THROUGH CABO CORRIENTES TO 
15N115W. THE TROUGH IS EXPECTED TO WEAKEN IN PLACE OVER THE NEXT 
DAY OR SO...BUT THE 70-90 KT UPPER JET ON ITS SE SIDE WILL 
REMAIN. THE REAR RIGHT QUADRANT OF THIS JET IS ENHANCING LIFT N 
OF THE ITCZ BETWEEN 95W-110W. PRECIPITABLE WATER VALUES ARE IN 
THE 1.75-2.00 INCH RANGE IN THIS AREA. SCATTERED SHOWERS...WITH  
ISOLATED THUNDERSTORMS FOUND S OF 08N...ARE NOTED VIA INFRARED 
SATELLITE IMAGERY AND LIGHTNING DATA WITHIN APPROXIMATELY 180 NM 
EITHER SIDE OF A LINE FROM 05N105W THROUGH PUERTO ANGEL AND INTO 
THE SW GULF OF MEXICO.

AN EXPANSIVE DEEP-LAYER LOW LIES N-NE OF THE HAWAIIAN ISLANDS. 
THE SOUTHWESTERLY UPPER JET ON THE SE SIDE OF THE LOW IS 
TRANSPORTING MOISTURE INTO WESTERN WATERS PRIMARILY W OF A LINE 
FROM 32N130W TO 15N140W...WITH SHOWER ACTIVITY BELIEVED TO BE 
FOUND MAINLY N OF 26N. THE COLD FRONT ASSOCIATED WITH THE UPPER 
LOW IS STILL W OF THE AREA FROM 32N142W TO 19N150W. SEVERAL 
SCATTEROMETER PASSES OVER THE PAST 8 HOURS HAVE CLIPPED NW 
WATERS AND SHOWN WINDS AT 20 KT OR HIGHER. SHIP WDC3786 REPORTED 
8 FT SEAS NEAR 27N138W AT 0000 UTC. THE UPPER LOW IS FORECAST TO 
WEAKEN AS IT MOVES NORTHEASTWARD TODAY...WITH ITS REMNANTS 
EXPECTED TO BE PICKED UP BY A NORTHERN STREAM TROUGH ON TUE. THE 
COLD FRONT IS EXPECTED TO BEGIN TO DISSIPATE S OF 32N AS IT 
MOVES INTO NW WATERS TONIGHT...WITH WINDS AND SEAS DROPPING 
BELOW ADVISORY CRITERIA BY 0000 UTC TUE. 

HIGH PRESSURE IN THE EASTERN PACIFIC HAS BEEN FORCED NORTHWARD 
BY THE AFOREMENTIONED DEEP-LAYER LOW. A RIDGE EXTENDS FROM A 
1028 MB HIGH NEAR 42N130W TO 30N129W. THE PRESSURE GRADIENT IS 
WEAK BETWEEN THE SUBTROPICAL HIGH AND THE ITCZ OVER WESTERN 
WATERS. TRADE WINDS HAVE BEEN REDUCED TO A MODERATE TO FRESH NE 
BREEZE OVER MOST OF THE AREA ACCORDING TO THE 0518 UTC AND 0700 
UTC ASCAT PASSES. WEAK HIGH PRESSURE WILL BE SQUEEZED S OF THE 
DEEP-LAYER LOW AS IT MOVES EASTWARD...BUT IT WILL WEAKEN 
CONSIDERABLY. THIS WILL KEEP TRADE WINDS BELOW ADVISORY CRITERIA 
THROUGH AT LEAST WED MORNING.

THE PRESSURE GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND 
TROUGHING OVER THE U.S. DESERT SW IS FORCING FRESH TO STRONG NW 
WINDS OFFSHORE OF SOUTHERN CALIFORNIA N OF THE AREA. WHILE WINDS 
S OF 30N ARE WEAKER...N-NW SWELL IS BEING PROPAGATED INTO NE 
FORECAST WATERS. SHIP 9HJI9 REPORTED 11 FT SEAS NEAR 30N122W AT 
0900 UTC. THE WINDS WILL DIMINISH AS THE SUBTROPICAL HIGH 
WEAKENS AND SEAS SHOULD SUBSIDE TO LESS THAN 8 FT BY THIS 
AFTERNOON.

$$
SCHAUER