000
AXPZ20 KNHC 282202
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON SEP 28 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.

...TROPICAL WAVE...
TROPICAL WAVE WAS ANALYZED ALONG 86W MOVING W 10-15 KT. NO 
SIGNIFICANT CONVECTION ASSOCIATED WITH THE WAVE ACROSS THE EPAC. 
A WIND SURGE MOVING ACROSS THE EXTREME SW CARIBBEAN WAS 
INITIATING SCATTERED MODERATE CONVECTION THERE SPREADING W INTO 
NICARAGUA. 

...ITCZ...
AXIS WAS ALONG 08N78W TO 09N86W TO 14N105W TO 14N119W TO 12N125W 
TO 14N140W. SCATTERED MODERATE WITHIN 180 NM EITHER SIDE OF AXIS 
BETWEEN 86W AND 95W AND WITHIN 120 NM N OF AXIS BETWEEN 120W AND 
123W. 

...DISCUSSION...

A LARGE SW-NE ELONGATED UPPER LEVEL CYCLONIC CIRCULATION IS 
CENTERED NEAR 28N137W WITH ASSOCIATED BROAD CYCLONIC FLOW N OF 
16-18N BETWEEN 125W 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 25N AND BETWEEN 130N AND 138W. AN ASSOCIATED 
45-65 KT SUBTROPICAL JET LIES ON THE SE SIDE OF THIS CYCLONIC 
CIRCULATION...EXTENDING THROUGH 20N129W TO 30N108W. THE CYCLONIC 
CIRCULATION WILL DIG SLOWLY SE THROUGH THIS EVENING...AS IT IS 
REINFORCED BY A LARGE UPPER TROUGH TO ITS N...WITH IMPARTED 
ENERGY PRODUCING A MORE SIGNIFICANT SSW MOTION AND ELONGATION OF 
THIS TROUGH OVER THE NEXT FEW DAYS. THIS WILL HELP TO EFFECT A 
BROAD OMEGA BLOCKING PATTERN ACROSS THE MID LATITUDES OF N 
AMERICA OVER THE NEXT FEW DAYS...SPANNING FROM 70W TO 140W.  
THIS PATTERN ALOFT WILL ALSO PREVENT THE SUBTROPICAL HIGH FROM 
REBUILDING SUBSTANTIALLY OVER THE NW WATERS AND SHOULD GENERALLY 
KEEP TRADE WINDS W OF 115W LIGHT. 

DOWNSTREAM...A RATHER FLAT UPPER LEVEL RIDGE IS LOCATED S AND SE 
OF THE CYCLONIC CIRCULATION...AND EXTENDED FROM CENTRAL MEXICO 
E INTO THE GULF OF MEXICO...AND SW UNDERNEATH THE BROAD UPPER 
RIDGE TO ANOTHER UPPER ANTICYCLONE CENTERED NEAR 12N152W. 
INDUCED CYCLONIC SHEAR BETWEEN THESE TWO UPPER HIGHS AND A 
CONVERGENT ASYMPTOTE WAS NOTED S OF 18N ALONG 123/124W.  
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 IN WATER VAPOR IMAGERY ALONG 96W MARCHING 
W ACROSS SE MEXICO AND THE ADJACENT TROPICAL EPAC...AND 
CONTINUED TO PRODUCE SCATTERED DEEP CONVECTIVE CELLS ACROSS THE 
EPAC IN ITS SE QUADRANT....WITH ISOLATED CONVECTION ALONG THE 
NRN SEMICIRCLE. GLOBAL MODELS DEPICT A LOW TO MID LEVEL VORT 
CENTER JUST TO THE E AND SE OF THIS TUTT LOW...MOVING W THROUGH 
THE ITCZ. 

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 THE PAST SEVERAL DAYS HAS CONTRIBUTED TO 
THE FORMATION OF BROAD CYCLONIC TURNING FROM 10N TO COASTAL 
MEXICO BETWEEN 99W AND 112W. SCATTERED TO LOCALLY NUMEROUS 
MODERATE CONVECTION EXTENDED FROM COASTAL MEXICAN COAST S OF 10N 
BETWEEN 99W AND 112W. SATELLITE IMAGERY AND A RECENT ASCAT PASS 
SUGGEST THAT A SURFACE LOW MAY BE DEVELOPING NEAR 15N106W. 
RECENT SCATTEROMETER PASSES HAVE ALSO SHOWN AN ELONGATED AREA OF 
E TO SE WINDS OF 20-25 KT N OF THE ITCZ AND N THROUGH E OF THIS 
LOW TO THE MEXICAN COAST...WHERE STEEP SEAS CONTINUE TO GROW 
CREATING ROUGH MARINE CONDITIONS. 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 1043 MB LOW 
NEAR 43N155W SE TO OFFSHORE OF BAJA CALIFORNIA NEAR 21N116W. 
THE ITCZ CONTINUED TO BE QUITE ACTIVE ACROSS SEVERAL ZONES IN 
THE AREA...UNDER GOOD DIFFLUENCE ALOFT. SEVERAL WAVES...LOWS AND 
PERTURBATIONS WERE EVIDENT IN VISIBLE SATELLITE IMAGERY THIS 
AFTERNOON. FIRST THE BROAD LOW AND CONVECTION OFF OF 
MEXICO...ANOTHER LARGE CYCLONIC CIRCULATION CENTERED NEAR 
13N119W...THE REMNANTS OF NORA...A 1011 MB LOW NEAR 17N131W...A 
TINY MESOCYCLONE TO THE SE NEAR 13.5N128.5W...AND ANOTHER LOW 
ALONG A WAVE AT 14N139W. 

REGIONAL SEAS ARE BEING DOMINATED BY MODERATE PERIOD SRN HEMI SE 
SWELL...AND LONGER PERIOD NW AND SSW SWELL. THE FRESH TO STRONG 
E TO SE FLOW ALONG THE MEXICAN COAST WAS GENERATING SEAS OF 7 TO 
10 FT IN THIS CONFUSED MIX. SEAS IN EXCESS OF 8 FT WILL 
GRADUALLY PROPAGATE NWD ACROSS THE EQUATOR TO 12N BY MID WEEK AS 
SEVERAL NEW PULSES OF LARGE SE AND SW SWELL MOVE INTO THE 
AREA.   

$$
STRIPLING