000
AXPZ20 KNHC 181725 AAA
TWDEP 

TROPICAL WEATHER DISCUSSION...UPDATED 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1725 UTC WED MAY 18 2016

UPDATED ITCZ/MONSOON TROUGH SECTION 

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 1200 UTC surface analysis and satellite imagery through
1700 UTC.     
  
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              

The monsoon trough axis extends from 10N84W to 07N93W to 08N105W
where earlier scatterometer winds indicated that it transitions
to the ITCZ axis to 10N113W to 07N125W to 09N135W. A trough is
along a position from 13N138W to w of the area near 07N142W.
Scattered moderate to strong convection exists from 05N-08N
between 83W-87W. Scattered moderate convection is within 180 nm
s of the axis between 94W-103W. 

...DISCUSSION...                                             

Strong high pres of 1035 mb is over the eastern North Pacific is
well to the northwest of the area near 41N150W, with a ridge
axis extending southeastward through 32N135W to 27N130W to near
14N108W. The pressure gradient between the ridge and the
ITCZ/monsoon trough to the southwest is supporting mainly
moderate to fresh trade winds. Winds are enhanced northwest of a
surface trough that extend from 13N138W to w of the area near
07N142W. ASCAT data from late last night indicated fresh to
strong northeast winds within 150 nm northwest of the trough
from 11N-13N. The subtropical high will shift northeastward over
the next 24 hours. The ridge axis will shift west and weaken as
deep-layer troughing builds over the southwestern United States
and over the northeast waters. This will cause the area of fresh
trade winds to diminish in coverage. The fresh to strong
northeast winds northwest of the trough will move to w of 140W
this evening. Deep convection noted earlier near the trough has
dissipated under very dry air aloft.  

Northwesterly to northerly swell that originated off the
California coast is producing seas to 8 ft to the north of 29N
between 123W-130W this morning. The aforementioned deep-layered
troughing building over the northeastern portion of the forecast
area will send a weak frontal boundary across the NE waters Thu
night...and force the subtropical ridge westward with the
northerly winds to the north of the area and the swell moving
into waters north of 28N expected to follow suit. Combined seas
to 9 ft are expected over northwestern forecast waters Wednesday
night through at least Friday morning.

Upper level diffluent flow occurring on the southeast periphery
of an upper level anticyclone centered to the southeast of the
Gulf of Tehuantepec is supporting clusters of scattered moderate
to strong convection over the far eastern portion of the area
from 06.5N-08N east of 83W. Conditions are forecast to remain
favorable for sustained convection in this area through Thursday
before available low-level moisture decreases...and winds aloft
becoming less favorable for vertical lift.

$$ 
Aguirre