000
AXPZ20 KNHC 270233 RRA
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI JUL 27 2012

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 
0215 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 21N113W TO 14N115W MOVING W-NW AT 
10-15 KT. THE WAVE REMAINS EMBEDDED WITHIN AN AREA OF DEEP LAYER 
MOISTURE AS DEPICTED ON THE MIMIC-TPW ANIMATION. A SMALL CLUSTER 
OF MODERATE CONVECTION IS NOTED NEAR THE NORTHERN END OF THE 
WAVE AXIS. COMPUTER MODEL GUIDANCE CONTINUES TO SUGGEST NO 
TROPICAL CYCLONE DEVELOPMENT WITH THIS FEATURE.

TROPICAL WAVE EXTENDS FROM 15N129W TO 08N134W. THE WAVE SHOWS UP 
WELL AS A MOISTURE SURGE ON THE TOTAL PRECIPITABLE WATER 
PRODUCT. MULTIPLE VORTICES ARE SPINNING ALONG THE WAVE AXIS 
BASED ON VISIBLE SATELLITE IMAGERY. THE ASSOCIATED SHOWER 
ACTIVITY REMAINS DISORGANIZED WITH ONLY ISOLATED MODERATE 
CONVECTION NEAR THE WAVE AXIS. UPPER-LEVEL WINDS ARE BECOMING 
LESS CONDUCIVE FOR DEVELOPMENT...AND THIS SYSTEM HAS NOW A LOW 
CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. 
THE WAVE WILL CONTINUE TO MOVE WESTWARD AND IS EXPECTED TO CROSS 
OVER INTO THE CENTRAL PACIFIC OCEAN ON SAT.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH IS ALONG 08N78W TO 09N90W. THE INTERTROPICAL 
CONVERGENCE ZONE AXIS EXTENDS FROM 09N90W TO 08N112W TO 11N128W 
THEN RESUMES W OF TROPICAL WAVE AT 08N136W TO BEYOND 07N140W. 
SCATTERED MODERATE TO ISOLATED STRONG S OF THE ITCZ AXIS TO 07N 
BETWEEN 95W AND 102W. SIMILAR CONVECTION IS NOTED WITHIN 210 NM 
S OF THE AXIS BETWEEN 110W AND 118W...AND BETWEEN 119W AND 125W. 

...DISCUSSION...
WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL ANTICYCLONIC 
CIRCULATION CENTERED NEAR 15N126W THAT EXTENDS A RIDGE AXIS 
NORTH-NORTHWESTWARD TO BEYOND 32N140W. TO THE EAST OF THIS RIDGE 
AXIS...THERE IS A SHORTWAVE TROUGH EXTENDING ALONG 125W N OF 
20N. MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY AIR MASS 
DOMINATES MUCH OF THE NORTHERN FORECAST WATERS MAINLY N OF 18N W 
OF 115W. ANOTHER ANTICYCLONIC CIRCULATION IS CENTERED OVER NW 
MEXICO NEAR 29N108W WITH A RIDGE ALONG THE PACIFIC COAST OF 
MEXICO TO NEAR 16N98W. UPPER DIFFLUENCE ASSOCIATED WITH THIS 
SYSTEM IS HELPING TO INDUCE SCATTERED TO NUMEROUS SHOWERS AND 
TSTMS OVER PARTS OF NORTHERN AND CENTRAL MEXICO. AN INVERTED 
TROUGH OVER THE SE PORTION OF THE GULF OF MEXICO EXTENDS INTO 
THE EPAC THROUGH THE GULF OF TEHUANTEPEC. THE REMAINDER OF THE 
DISCUSSION AREA E OF 120W IS UNDER THE INFLUENCE OF PRIMARILY 
EASTERLY WINDS ALOFT.  

A SURFACE RIDGE EXTENDS FROM A 1031 MB HIGH PRESSURE CENTERED 
NEAR 38N147W TO 23N115W. THE PRESSURE GRADIENT BETWEEN THE 
SURFACE RIDGE AND LOWER PRESSURE IN THE VICINITY OF THE ITCZ IS 
MAINTAINING FRESH TRADE WINDS FROM 11N TO 17N W OF 128W. THE 
1852 UTC ASCAT PASS PROVIDED OBSERVATIONS OF THESE WINDS. THE 
AREA OF FRESH TRADES WILL SHIFT WESTWARD WITH THE TROPICAL WAVE 
ALONG 15N129W TO 08N134W

GAP WINDS OF 20-25 KT ARE EXPECTED TO PERSIST OVER THE GULF OF 
PAPAGAYO AS FRESH TO STRONG TRADE WINDS CONTINUE TO BLOW ACROSS 
THE SW CARIBBEAN. THE WINDS WILL PEAK DURING THE LATE NIGHT AND 
EARLY MORNING HOURS...PARTICULARLY ON SAT...WITH THE ASSISTANCE 
OF THE NOCTURNAL DRAINAGE FLOW. 

$$
GR