000
AXPZ20 KNHC 171616
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT AUG 17 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 09N74W TO 11N87W TO 
DEVELOPING LOW PRES NEAR 09.5N98W 1008 MB TO 17N108W TO LOW PRES 
NEAR 15N113.5W 1011 MB TO 12N117W TO LOW PRES NEAR 13.5N124.5W 
1011 MB TO 11N130W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING 
ON TO BEYOND 07N140W. SCATTERED MODERATE TO STRONG CONVECTION 
NOTED WITHIN 120 NM EITHER SIDE OF TROUGH 87W. SCATTERED 
MODERATE TO STRONG CONVECTION NOTED WITHIN 120 NM S OF AXIS 
BETWEEN 101W AND 108W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION NOTED WITHIN 180 NM N OF AXIS W OF 126W. SCATTERED 
MODERATE TO STRONG CONVECTION NOTED FROM 08N TO 14N BETWEEN 92W 
AND 101W. 

...DISCUSSION...
BROAD UPPER ANTICYCLONE IS CENTERED NEAR 23N125W AND IS SHIFTING 
W...WITH ASSOCIATED RIDGE EXTENDING NE TO 26N119W AND W-SW TO 
20N141W. MIDDLE TO UPPER TROUGH LIES TO THE NW OF RIDGE WITH 
DEEP LAYERED UPPER CYCLONE ALONG 126W AND OFFSHORE OF CALIFORNIA 
SHIFTING SLOWLY E-NE...WITH TROUGH TRAILING SW TO ELONGATING MID 
LEVEL CYCLONE NEAR 23N145W. TO THE E OF RIDGE IS A WWD MOVING 
MIDDLE/UPPER CYCLONE NEAR 21N114W AND IS ABUTTING AGAINST THE E 
SIDE OF RIDGE. THIS LOW IS FORECAST TO WEAKEN AND LIFT NWD OVER 
THE NEXT FEW DAYS IN RESPONSE TO UPPER LOW OFF CALIFORNIA. 
OTHERWISE...PROGRESSIVE ELY FLOW ALOFT PREVAILS S OF 17N ACROSS 
THE AREA BETWEEN 90W AND 130W...AND IS VENTING CONVECTION ALONG 
THE MONSOON TROUGH FAVORABLY. 

AT THE SURFACE...A 1026 MB HIGH IS CENTERED NEAR 36N145W AND 
EXTENDS A BROAD BUT WEAK RIDGE SE TO NEAR 20N113W. A WEAK PRES 
GRADIENT BETWEEN THIS HIGH AND THE LOWER PRES ALONG THE W SLOPES 
OF THE SIERRA MADRES OCCIDENTALES IS YIELDING NNW AROUND 15 KT 
OFF THE W COAST OF BAJA CALIFORNIA EXTENDING WWD TO 117W...PER 
OVERNIGHT SCATTEROMETER PASSES...WHERE SEAS ARE RUNNING 4-5 FT.

A PAIR OF LOW PRES CENTERED MENTIONED ABOVE ARE EMBEDDED WITHIN 
THE W HALF OF THE MONSOON TROUGH AND YIELDING SMALL AREAS OF 
MODERATE CONVECTION AS THEY SHIFT SLOWLY W. A RATHER LARGE 
CLUSTER OF CONVECTION CONTINUES THIS MORNING ALONG BOTH SIDES OF 
THE MONSOON TROUGH BETWEEN 92W AND 104W. OVERNIGHT SCATTEROMETER 
PASSES SHOWED AN ELONGATED CYCLONIC CIRCULATION ABOUT THE TROUGH 
THERE...WITH NOCTURNAL CONVECTION SHIFTING SW OFF OF MEXICO AND 
CENTRAL AMERICA LINGERING NO OF THE TROUGH THIS MORNING...AND 
SCATTERED CONVECTION S OF THE TROUGH TRIGGERED BY CONVERGENCE S 
OF THE TROUGH. A LARGE POOL OF ABUNDANT TROPICAL MOISTURE EXISTS 
WITHIN THIS BROAD CIRCULATION...MAINTAINING A VERY UNSTABLE 
ENVIRONMENT. SOME WAVE ENERGY FROM THE S END OF THE WAVE THAT 
HAS INITIATED THE DISTURBED WEATHER IN THE W GULF OF MEXICO HAS 
LIKELY CONTRIBUTED TO THIS AREA OF CONVECTION. MODEL GUIDANCE 
SUGGESTS THIS WEATHER WILL GENERALLY SHIFT W TO W-NW OVER THE 
NEXT FEW DAYS...WITH THE ECMWF BECOMING VERY AGGRESSIVE WITH 
TROPICAL DEVELOPMENT BY WEDNESDAY. FOR THE TIME BEING...THIS 
SOLUTION IS BEING DISCOUNTED FOR A WEAKER AND MORE WWD MOVING 
WAVE.
 
$$ 
STRIPLING