000
AXPZ20 KNHC 200235
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
0405 UTC SAT JUL 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0215 UTC.

...TROPICAL WAVES...                                            
A TROPICAL WAVE EXTENDS FROM 19N111W TO 13N114W MOVING W ABOUT 
10 KT. CONVECTION IS NOW LIMITED IN ASSOCIATION WITH THE WAVE. 
ONLY ISOLATED TO SCATTERED SHOWERS AND LIKELY ISOLATED TSTMS ARE 
NOTED NEAR THE WAVE AXIS. THIS FEATURE STILL SHOWS UP WELL AS A 
HIGH AMPLITUDE MOISTURE SURGE IN TOTAL PRECIPITABLE WATER 
IMAGERY. GLOBAL MODELS CONTINUE TO SUGGEST THAT THE WAVE WILL 
GRADUALLY LOSE ITS SURFACE IDENTITY AS IT TRACKS WESTWARD 
THROUGH THE NEXT COUPLE OF DAYS. IN FACT...CONVECTION HAS 
GREATLY DIMINISHED COMPARED TO YESTERDAY.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...        
MONSOON TROUGH EXTENDS FROM 09N84W TO 10N95W TO 07N105W TO 
12N120W TO 10N130W. ITCZ AXIS EXTENDS FROM 10N130W TO 08N140W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 210 
NM N OF TROUGH BETWEEN 92W AND 96W. SCATTERED MODERATE 
CONVECTION IS FROM 12N TO 16N BETWEEN 118W AND 129W...FROM 07N 
TO 10N BETWEEN 134W AND 136W AND FROM 10N TO 14N W OF 134W. 

...DISCUSSION...                                          
ALOFT...AN ANTICYCLONE LOCATED WEST OF AREA NEAR 15N145W EXTENDS 
A RIDGE EWD ACROSS THE WEST-CENTRAL WATERS TO NEAR 15N130W. AN 
UPPER LEVEL TROUGH STRETCHES FROM 28N132W TO 21N130W TO 17N130W. 
SW WIND FLOW ALOFT DOMINATES THE NW CORNER OF THE AREA AHEAD OF 
A BROAD UPPER TROUGH LOCATED NW OF THE DISCUSSION REGION WITH 
AXIS CURRENTLY NEAR 150W. SATELLITE WATER VAPOR IMAGERY SHOWS 
MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY AND VERY STABLE 
AIR MASS ACROSS MUCH OF THE AREA N OF 17N W OF 126W. SOME HIGH 
CLOUDS ARE MOVING ACROSS THE NW CORNER OF THE REGION UNDER THE 
SW WIND FLOW. AN ANTICYCLONE CENTERED ALONG THE COAST OF MEXICO 
NEAR 23N106W EXTENDS A RIDGE OVER MUCH OF NORTH-CENTRAL MEXICO 
WITH THE EXCEPTION OF THE NW PART WHERE A WELL DEFINED DEEP 
LAYER LOW SITUATED NEAR 29N111W CONTINUES TO GENERATE SOME 
SHOWER AND TSTM ACTIVITY THERE. ANOTHER RIDGE EXTENDING FROM THE 
FOUR CORNER REGION IN U.S. COVERS THE NE PART OF THE FORECAST 
AREA BETWEEN THE AFOREMENTIONED UPPER LOW OVER NW MEXICO AND THE 
TROUGH TO THE WEST. ELY WINDS ALOFT ARE NOTED ACROSS MUCH OF THE 
AREA N OF 05N AND E OF ABOUT 110W. THESE WINDS ARE TRANSPORTING 
DEBRIS CLOUDINESS FROM CONVECTION ALONG AND NEAR THE MONSOON 
TROUGH. 

AT THE SURFACE...A RIDGE DOMINATES THE FORECAST WATERS N OF 15N 
W OF 116W ANCHORED BY A 1027 MB HIGH LOCATED NEAR 35N137W. NW 
WINDS OF 10-15 KT ARE JUST WEST OF BAJA CALIFORNIA BETWEEN THIS 
RIDGE AND LOWER PRES OVER WESTERN MEXICO. A SMALL AREA OF 20 KT 
NE WINDS AND SEAS TO 8 FT IS STILL NOTED N OF 13N AND W OF LINE 
FROM 18N140W TO 13N136W. THE STRONGEST WINDS OF 20-25 KT ARE NOW 
JUST W OF AREA. 

A TIGHT PRES GRADIENT BETWEEN THE COAST OF NORTHERN CALIFORNIA 
AND 127W WILL INCREASE WINDS TO NEAR GALE FORCE. SEAS ASSOCIATED 
WITH THESE STRONG WINDS ARE EXPECTED TO PROPAGATE SOUTH AS 
NORTHERLY SWELLS REACHING THE FAR NORTH WATERS BY EARLY SAT. 
THIS SWELL EVENT WILL PERSIST THROUGH SUN AFFECTING MAINLY THE 
WATERS N OF 28N BETWEEN 122W AND 130W WITH SEAS TO NEAR 9 FT. 

$$ 
GR