000
AXPZ20 KNHC 181618
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN AUG 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.
                                    
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...       
MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 08.5N75W TO 09N83W TO 
11N91W TO 10N100W TO LOW PRES AT 16N113.5W 1009 MB TO 11.5N119W 
TO 12N127W TO 12.5N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION NOTED WITHIN 300 NM S OF TROUGH BETWEEN 80W AND 91W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 120 
NM N AND 210 NM S OF TROUGH BETWEEN 100W AND 109W. SCATTERED 
MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM NW OF TROUGH 
BETWEEN 115W AND 120W...AND WITHIN 120 NM N OF TROUGH W OF 122W. 
SCATTERED MODERATE TO STRONG CONVECTION OCCURRING WITHIN 150 NM 
OF MEXICAN COASTLINE BETWEEN 96W AND 108W.

...DISCUSSION...                                              
BROAD UPPER LEVEL ANTICYCLONE CENTERED NEAR 21.5N133W AND 
DRIFTING W CONTINUES TO DOMINATE MOST OF NW PORTION OF AREA. 
DIFFLUENT FLOW ALOFT ACROSS SW PERIPHERY OF ASSOCIATED RIDGE 
AIDING IN SUSTAINING ACTIVE CONVECTION NEAR MONSOON TROUGH W OF 
132W. ELONGATING MIDDLE/UPPER CYCLONE NEAR 22N117W WITH 
TROUGHING EXTENDING SSW TO 18N120W BEING STRETCHED NNE TO SSW... 
WITH MAJORITY OF ENTRAINED MOISTURE AND ENERGY BEING PULLED NWD 
IN RESPONSE TO DIGGING DEEP LAYERED CYCLONE ALONG COAST OF 
CENTRAL CALIFORNIA. THIS MID LATITUDE TROUGH IS FORECAST TO DIG 
SSW AND S OF 20N ALONG 125W BY LATE TUE...ALLOWING SHARP HIGH 
AMPLITUDE RIDGE CURRENTLY ACROSS W AND NW MEXICO TO SHIFT W TO 
JUST OFFSHORE OF S HALF OF BAJA CALIFORNIA. PRESENTLY...UPPER 
DIVERGENCE BETWEEN THIS RIDGE AND DEEP LAYERED TROUGH ACROSS 
CENTRAL U.S. EXTENDING SSW TO CENTRAL MEXICO AIDING IN 
SUSTAINING VERY ACTIVE NOCTURNAL CONVECTION THAT HAS PUSHED SW 
OFF THE W COAST OF MEXICO...AS DESCRIBED ABOVE. PROGRESSIVE 
EASTERLY FLOW ALOFT OTHERWISE PREVAILS ACROSS THE AREA S OF 15N. 

...AT THE LOWER LEVELS...
SURFACE HIGH PRES CENTER NW OF AREA AT 37N141W EXTENDS BROAD 
RIDGE SE TO NEAR 21N116W...WHERE THE ELONGATED ELONGATING 
MIDDLE/UPPER CYCLONE HAS CARVED A WEAKNESS INTO THE LOWER 
LEVELS. A BROAD 1009 MB SURFACE LOW WAS CENTERED NEAR 16N113.5W 
AND EMBEDDED WITHIN THE MONSOON TROUGH. LOW LEVEL CONVERGENCE 
ALONG THE W SIDE OF THE MONSOON TROUGH THERE WAS PRODUCING 
CONVECTION DESCRIBED ABOVE. A MODEST PRES GRADIENT BETWEEN THE 
SURFACE HIGH AND TROUGHING ACROSS THE BAJA CALIFORNIA PENINSULA 
WAS PRODUCING MODERATE NNW WINDS AROUND 15 KT THIS MORNING OFF 
THE BAJA COASTLINE...WHERE SEAS WERE RUNNING 4 TO 5 FT. S OF THE 
NE PACIFIC RIDGE...A MODEST PRES GRADIENT WAS YIELDING NE TO ENE 
TRADES AROUND 20 KT W OF 134W...FROM 16N TO THE TROUGH AXIS 
ALONG 11N...AND WAS FORCING SCATTERED CONVECTION THERE. 

E OF 110W...A SERIES OF EASTERLY WAVES APPEAR TO BE PROPAGATING 
WWD THROUGH THE TROPICS...ONE ALONG ABOUT 110W...A SECOND ALONG 
102W...AND POSSIBLY A THIRD ALONG 91W. ABUNDANT TROPICAL 
MOISTURE IN THE VICINITY OF THESE WAVES IS PROVIDING AN UNSTABLE 
ENVIRONMENT FOR ACTIVE CONVECTION ACROSS THIS REGION. COMPUTER 
MODEL GUIDANCE SUGGESTS THAT THESE WAVES WILL CONTINUE WWD AND 
CREATE A FAVORABLE REGION ALONG THE MONSOON TROUGH BETWEEN 100W 
AND 115W DURING THE NEXT SEVERAL DAYS...THAT COULD YIELD ONE OR 
MORE SURFACE LOWS...WHICH COULD POTENTIALLY DEVELOP INTO 
TROPICAL CYCLONES. BASED ON THIS SCENARIO...THIS REGION HAS A 
HIGH CHANCE FOR TROPICAL DEVELOPMENT IN THE NEXT 5 DAYS. 
 
$$ 
STRIPLING