000
AXPZ20 KNHC 281603
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON SEP 28 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1515 UTC.

...TROPICAL WAVE...
TROPICAL WAVE WAS ANALYZED ALONG 85W MOVING W 10-15 KT. NO 
SIGNIFICANT CONVECTION ASSOCIATED WITH THE WAVE.

...ITCZ...
AXIS WAS ALONG 08N86W TO 13N104W TO 13N115W TO 15N128W TO 
14N138W. SCATTERED TO ISOLATED MODERATE WAS WITHIN A FEW DEGREES 
TO THIS AREA...AND COULD BE ATTRIBUTED TO THE S AMERICAN 
MONSOONAL CIRCULATION AS MUCH AS A TROPICAL WAVE. 

...DISCUSSION...

W OF 100W...
LARGE SW-NE ELONGATED UPPER LEVEL CYCLONIC CIRCULATION IS 
CENTERED NEAR 28N138W WITH ASSOCIATED BROAD CYCLONIC FLOW N OF 
18-20N BETWEEN 120W AND 150W. THE TYPICAL BROKEN STRATOCUMULUS 
FIELD ACROSS THE COOL WATERS OF THE PACIFIC...CURRENTLY N OF 20N 
AND W OF 134W...IS BEING ENHANCED UNDERNEATH THE SE QUADRANT OF 
THIS UPPER LOW...YIELDING SCATTERED AREAS OF MULTILAYERED CLOUDS 
AND STRATIFORM PRECIP...POSSIBLY WITH VERY ISOLATED ELEVATED 
CONVECTION...N OF 24N AND BETWEEN 130N AND 139W. AN ASSOCIATED 
55-65 KT SUBTROPICAL JET LIES ON THE SE SIDE OF THIS CYCLONIC 
CIRCULATION...EXTENDING THROUGH 21N129W TO 29N114W. THE CYCLONIC 
CIRCULATION WILL DIG SLOWLY SE THROUGH THIS EVENING AND THEN 
MORE SIGNIFICANTLY SSW OVER THE NEXT FEW DAYS AS A BROAD OMEGA 
BLOCKING PATTERN BECOME ESTABLISHED ACROSS THE MID LATITUDES OF 
N AMERICA. THIS PATTERN ALOFT WILL ALSO PREVENT THE SUBTROPICAL 
HIGH FROM REBUILDING SUBSTANTIALLY OVER NW WATERS AND SHOULD 
GENERALLY KEEP TRADE WINDS LIGHT. 

DOWNSTREAM...A RATHER FLAT UPPER LEVEL RIDGE IS LOCATED SE OF 
THE CYCLONIC CIRCULATION AND EXTENDED FROM THE GULF OF MEXICO 
WWD ACROSS CENTRAL OLD MEXICO AND THEN SW UNDERNEATH THE BROAD 
UPPER RIDGE TO ANOTHER UPPER ANTICYCLONE CENTERED NEAR 13N150W. 
GENERALLY DRY AND SUBSIDENT CONDITIONS COULD BE FOUND ACROSS THE 
BASE OF THE UPPER TROUGH...AND ACROSS THE NW AND NRN FLANKS OF 
THE RIDGE...JUST SE OF THE SUBTROPICAL JET. A TUTT LOW WAS 
EVIDENT ALONG 94W MOVING W ACROSS SRN MEXICO AND THE BAY OF 
CAMPECHE AND IGNITING SCATTERED DEEP CONVECTIVE CELLS ACROSS THE 
EPAC IN ITS SE QUADRANT. 

A LOW TO MID LEVEL TROUGH THAT HAS BEEN TRACKED FROM ACROSS THE 
FAR W CARIB...CENTRAL AMERICA...AND THEN S CENTRAL MEXICO AND 
THE ADJACENT PACIFIC HAS AIDED IN THE INITIATION OF A LARGE 
CLUSTER OF NOCTURNAL CONVECTION ACROSS THE W COAST OF MEXICO 
THAT HAS LINGERED THROUGH THIS MORNING UNDERNEATH EXCELLENT 
UPPER DIVERGENCE ASSOCIATED WITH AN UPPER HIGH 21N105W...PART OF 
THE ABOVE UPPER RIDGE. BROAD AND WEAK CYCLONIC TURNING ALSO 
ASSOCIATED WITH THIS LOW TO MID LEVEL TROUGH WAS ALSO INITIATING 
SCATTERED TO LOCALLY NUMEROUS MODERATE CONVECTION JUST OFFSHORE 
OF THE MEXICAN COAST S OF 12N BETWEEN 99W AND 109W. GLOBAL 
MODELS HAS BEEN SUGGESTING IN RECENT DAYS THAT THIS AREA OF 
CYCLONIC TURNING AND ACTIVE CONVECTION MAY YIELD AN ORGANIZED 
LOW IN THE NEXT SEVERAL DAYS AS THIS FEATURE MOVES OFF TO THE 
WNW. SOME OF THE ENERGY ASSOCIATED WITH THIS LOW TO MID LEVEL 
TROUGH IS ASSUMED TO HAVE ORIGINATED OVER AFRICA AND WAS A 
PORTION OF A LONG AGO FRACTURED TROPICAL WAVE. 

AT THE SURFACE...A HIGH PRES RIDGE EXTENDED FROM A 1041 MB LOW 
NEAR 45N157W SE TO OFFSHORE OF BAJA CALIFORNIA NEAR 20N11W. THE 
REMNANT LOW OF NORA...1009 MB...WAS CENTERED NEAR 
17.5N130W...MOVING SLOWLY WSW...AND IS EXPECTED TO DISSIPATE 
TONIGHT OR EARLY MONDAY. THERE IS NO SIGNIFICANT CONVECTION 
ASSOCIATED WITH THIS LOW. 

THE ITCZ CONTINUED TO BE QUITE ACTIVE ACROSS SEVERAL ZONES IN 
THE AREA...UNDER GOOD DIFFLUENCE ALOFT. SEVERAL WAVES AND 
PERTURBATIONS WAS ANALYZED ALONG THE ITCZ...A TROPICAL WAVE 
ALONG 85W...ANOTHER WAVE ALONG 105/106W...THE REMNANT LOW OF 
NORA ALONG 130W...AND ANOTHER ALONG 139W.  

$$
STRIPLING