000
AXPZ20 KNHC 180930
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED JUL 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0800 UTC.

...SPECIAL FEATURES... 
TROPICAL DEPRESSION FABIO IS CENTERED NEAR 24.9N 120.6W AT 
18/0900 UTC OR ABOUT 400 NM SW OF PUNTA BAJA MEXICO AND ABOUT 
505 NM S-SW OF SAN DIEGO CALIFORNIA MOVING N AT 9 KT. ESTIMATED 
MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND 
SPEED IS 30 KT WITH GUSTS TO 40 KT. SCATTERED MODERATE 
CONVECTION LIES BETWEEN 120 NM AND 330 NM IN THE N QUADRANT. 
FABIO IS BEING STEERED NORTHWARD ON THE LEADING EDGE OF A DEEP 
LAYERED TROUGH THAT EXTENDS NORTHWARD TO NORTHERN CALIFORNIA. 
FABIO IS FORECAST TO WEAKEN TO A REMNANT LOW BY THIS AFTERNOON 
AS IT ENCOUNTERS COOLER WATERS...A DRIER AIR MASS...AND 
INCREASING VERTICAL WIND SHEAR. SEE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 07N77W TO 08N99W TO 
13N106W TO 1007 MB LOW PRES NEAR 09N114W TO 07N118W TO 08N125W. 
THE ITCZ AXIS WAS ANALYZED FROM 08N125W TO 10N129W TO 10N140W. 
SCATTERED MODERATE TO STRONG CONVECTION LIES WITHIN 120 NM S OF 
THE AXIS BETWEEN 99W AND 103W. SCATTERED MODERATE CONVECTION IS 
WITHIN 210 NM NE SEMICIRCLE AND 150 NM SW SEMICIRCLE OF THE LOW 
PRES SYSTEM...EXCEPT SCATTERED MODERATE TO STRONG CONVECTION 
FROM 75NM TO 180 NM N QUADRANT. SCATTERED MODERATE CONVECTION IS 
WITHIN 180 NM N OF AXIS BETWEEN 118W AND 124W.

...DISCUSSION...
A 1036 MB SUBTROPICAL HIGH IS CENTERED WELL NW OF THE FORECAST 
AREA NEAR 43N151W WITH A RIDGE AXIS EXTENDING NORTH OF FABIO TO 
29N116W. A DEEP LAYER TROUGH IS CENTERED OVER COASTAL NORTHERN 
CALIFORNIA AND EXTENDS AN UPPER LEVEL TROUGH AXIS S-SW FROM AN 
UPPER LOW NEAR 42N123W TO 25N130W. THE SURFACE PRESSURE GRADIENT 
HAS RELAXED SUFFICIENTLY OVER NW PORTIONS TO KEEP WINDS A 
MODERATE BREEZE OR WEAKER. OTHERWISE...FABIO REMAINS THE ONLY 
FEATURE WITH WINDS ABOVE 20 KT AND SEAS GREATER THAN 8 FT. BY 
EARLY THU...SOUTHERN HEMISPHERIC SOUTHWESTERLY SWELL BUILDS SEAS 
TO 8 FT GENERALLY S OF 03N BETWEEN 108W AND 122W.

A BROAD ANTICYCLONIC CIRCULATION ALOFT SPANS MUCH OF THE REGION 
FROM 02N TO 22N BETWEEN 100W AND 130W. DIFFLUENCE ON THE 
SOUTHERN PERIPHERY OF THE ANTICYCLONE AND IS ENHANCING 
CONVECTION ALONG THE MONSOON TROUGH. A BROAD 1007 MB LOW IS 
ALONG THE MONSOON TROUGH AXIS NEAR 09N114W AND IS EXPECTED TO 
DRIFT SLOWLY WESTWARD OVER THE FEW DAYS. THE MODERATE TO STRONG 
CONVECTION ASSOCIATED WITH THIS LOW IS DESCRIBED IN THE SECTION 
ABOVE. THERE IS CURRENTLY ONLY A LOW RISK OF THIS SYSTEM 
BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HOURS. THE UPPER 
LEVEL ANTICYCLONE WILL SHRINK 10 DEGREES ON ITS EASTERN EDGE 
TODAY INTO EARLY THURSDAY AS AN INVERTED UPPER LEVEL TROUGH 
CURRENTLY E OF 100W MOVES WESTWARD. THE ANTICYCLONE SHOULD 
WEAKEN FURTHER BY EARLY FRI. 

GAP WINDS...NE TO E WINDS HAVE BEEN PULSING TO AS HIGH AS A 
STRONG BREEZE DURING THE MORNING HOURS DOWNWIND OF THE GULF OF 
TEHAUNTEPEC THE LAST FEW DAYS. WIND ARE EXPECTED TO BECOME MORE 
CONSISTENTLY FRESH TO STRONG BY EARLY THU AFTER A TROPICAL WAVE  
MOVES THROUGH MUCH OF CENTRAL AMERICA AND W OF THE GULF. 

$$
SCHAUER