000
AXPZ20 KNHC 182221
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
2205 UTC FRI SEP 18 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.               

...SPECIAL FEATURES...

THE ELONGATED AREA OF LOW PRES EXTENDS FROM A FEW HUNDRED MILES 
S OFF THE SOUTHERN TIP OF CALIFORNIA...SOUTHWESTWARD INTO THE 
TROPICS...WITH A PAIR OF LOW PRESSURE CENTERS EMBEDDED NEAR EACH 
END...LOCATED NEAR 16.5N111.5W AND 16N119.5W. SATELLITE IMAGERY 
IS SHOWING PERSISTENT ACTIVE CONVECTION IN ASSOCIATION WITH THIS 
MONSOONAL LIKE CIRCULATION...WITH SCATTERED MODERATE TO STRONG 
CONVECTION WITHIN 270 NM ACROSS THE W SEMICIRCLE OF THE EASTERN-
MOST LOW...AND SCATTERED STRONG CONVECTION WITHIN 120 NM ACROSS 
THE NW SEMICIRCLE OF THE WESTERN-MOST LOW. AFTERNOON 
SCATTEROMETER DATA SHOWED WINDS GENERALLY 15-20 KT SURROUNDING 
THIS ELONGATED CIRCULATION. 

GLOBAL MODELS CONTINUE TO INDICATE THAT THIS ELONGATED AREA OF 
LOW PRES WILL ROTATE COUNTER CLOCKWISE...AND BECOME MORE NE TO 
SW ALIGNED TONIGHT THROUGH FRIDAY...AND CONTINUE TO ADVECT 
ABUNDANT TROPICAL MOISTURE TOWARDS CENTRAL AND SOUTHERN BAJA 
CALIFORNIA AS WELL AS THE ADJACENT GULF AND MEXICAN STATES TO 
THE E. THE MOISTURE SHOULD THEN SPREAD FARTHER NW-N ACROSS 
NORTHERN BAJA CALIFORNIA SAT AND SAT NIGHT AS THE ELONGATED LOW 
PRES AREA BEGINS TO SHIFT N-NW. INCREASING RAIN CHANCES SHOULD 
BE EXPECTED ACROSS THESE AREAS...EXTENDING INLAND ACROSS 
MAINLAND MEXICO TO THE W SLOPES OF THE SIERRA MADRES 
OCCIDENTALES...WITH THE POTENTIAL FOR HEAVY RAINS...FLASH 
FLOODING AND LANDSLIDES THROUGH THE WEEKEND. THERE IS SOME 
POTENTIAL FOR THE EASTERN MOST LOW TO IMPROVE IN ORGANIZATION 
DURING THE NEXT 48 HOURS...AND THIS SYSTEM HAS A MEDIUM CHANCE 
FOR DEVELOPMENT INTO A TROPICAL CYCLONE AS IT MOVES NW TO N-NW.

...TROPICAL WAVES... 

A TROPICAL WAVE IS INVOF 84W-85W AND EXTENDS ACROSS CENTRAL 
AMERICA AND INTO THE NW CARIBBEAN...MOVING W 10-15 KT. SCATTERED 
SHOWERS AND TSTMS ARE NOTED BEHIND THE WAVE AXIS EXTENDING FROM 
CARIBBEAN COASTAL AREAS OF HONDURAS AND NICARAGUA SE INTO THE SW 
CARIBBEAN...WHILE ACTIVITY AHEAD OF THE WAVE IS MORE ISOLATED 
ACROSS PACIFIC COASTAL AREAS OF HONDURAS AND NICARAGUA.
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            

THE MONSOON TROUGH AXIS EXTENDS FROM COASTAL COLOMBIA NEAR 
11N74W TO 08N82W TO 10N93W TO LOW PRES NEAR 06N101W...WHERE IT 
HAS FRACTURED...THEN RESUMES FROM 22N110W TO LOW PRES NEAR 
16.5N111.5W TO LOW PRES NEAR 16N119.5W TO 12N132W TO BEYOND 
11N140W. SCATTERED STRONG CONVECTION NOTED FROM 04N TO 10N E OF 
81W. ISOLATED TO SCATTERED MODERATE TO STRONG CONVECTION NOTED 
WITHIN 150 NM N AND 240 NM S OF TROUGH BETWEEN 122W AND 138W.
 
...DISCUSSION...

WELL TO THE NW OF THE ELONGATED AREA OF LOW PRES...A 1023 MB 
HIGH PRES CENTER IS ANALYZED N OF THE HAWAIIAN ISLANDS NEAR 
35N150W WITH A RIDGE EXTENDING E THEN SE TO NEAR 21N114W. THE 
PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES IN THE TROPICS IS 
RESULTING IN FRESH TO STRONG NE TRADE WINDS WITHIN 180 NM NW OF 
A LINE FROM 18N140W TO 20N130W...WHERE SEAS ARE IN THE RANGE OF 
7-9 FT. THIS AREA OF FRESH TO STRONG NE TRADE WINDS IS FORECAST 
TO SHRINK IN COVERAGE AS IT SHIFTS W THROUGH SUN. ELSEWHERE... 
MODERATE TO FRESH NE TRADES ARE FOUND FROM ABOUT 16N TO 22N W OF 
124W...PER AFTERNOON SCATTEROMETER DATA...WHERE SEAS ARE IN THE 
5-7 FT RANGE. THE RIDGE WILL SHIFT SLIGHTLY EWD DURING THE NEXT 
48 HOURS...WHILE THE ELONGATED LOW PRES REALIGNS NE TO 
SW...WHICH WILL ACT TO DIMINISH THESE TRADES SLIGHTLY.
 
TO THE E OF THE RIDGE...NWLY WINDS OF 10-15 KT WERE DEPICTED BY 
AFTERNOON SCATTEROMETER DATA...WHERE SEAS ARE GENERALLY 
GENERALLY 4-5 FT IN MIXED SW AND NW SWELL. THE EASTERN PORTION 
OF THE RIDGE WILL WEAKEN SLIGHTLY OVER THE NEXT FEW DAYS...AS 
THE N PORTION OF THE ELONGATED LOW PRES AREA LIFTS N OF 
20N...PRODUCING WEAKENING WINDS ALONG THE WATERS W OF BAJA 
CALIFORNIA. HOWEVER...INCREASING WINDS ACROSS THE OFFSHORE 
WATERS OF CALIFORNIA WILL GENERATE A NEW PULSE OF NNW SWELL THAT 
WILL MOVE INTO NE PORTIONS OF THE DISCUSSION AREA OVER THE 
WEEKEND AND RAISE SEA HEIGHTS TO 6-8 FT...MAINLY W OF 118W. 
OTHERWISE...SEAS WILL CONTINUE TO BE DOMINATED BY PULSES OF 
MODERATE SW SOUTHERN HEMISPHERIC SWELL.
  
$$
STRIPLING