axpz20 knhc 210951
Tropical weather discussion
NWS National Hurricane Center Miami FL
1005 UTC Tue may 21 2013
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
Based on 0600 UTC surface analysis and satellite imagery through
...Intertropical convergence zone/monsoon trough...
The monsoon trough axis extends W and then NW from the
Colombia/Panama border at 08n78w across the extreme southern
tip of Panama to 10n87w to 10n107w...then turns WSW to 08n116w
...Then NW to 12n126w where it loses identity. Scatterometer
winds indicate an ITCZ forms SW of the remnants of Alvin at
12n127w and continues SW to beyond 09n140w. Scattered moderate
isolated strong convection is observed to the E of 120w within
150 nm of monsoon trough axis...and also within 75 nm of ITCZ
axis between 131w and 137w.
A tropical wave currently in the eastern Caribbean will reach
the SW Caribbean on Wed night. Model guidance is suggesting a
surface low will form along the monsoon trough axis near 11n81w
as the tropical wave moves into the monsoon trough. A second
low pressure is also expected to develop along the monsoon
trough axis in the Pacific waters near 10n86w Wed night into
Thu...with the low meandering in that area into the weekend.
Model guidance suggests the northerly drainage flow will
increase to 20 kt in the Gulf of Tehuantepec on Fri night and
gradually increase to 20-25 kt on Sat night through sunrise
A surface ridge extends from NW to se from 32n135w to 20n110w.
NW winds are currently at 10-15 kt along the entire W shore of
the Baja California peninsula with seas of 4-5 ft. Northerly
winds at 15-20 kt continue across the N-central Pacific waters
to the N of 30n between 120w-130w with seas maxing at 8 ft in
the associated N swell that continues to mix with long period
cross-equatorial SW swell. A reinforcing N surge at 20 to 25 kt
will arrive along 32n later today with only 20 kt winds
spreading S across the Pacific waters to the N of 20n between
115w-140w on Thu night...with seas building 8 to 13 ft in long
period N swell on Wed into Thu near 30n120w. Seas of 6-8 ft are
expected to reach along the Baja Peninsula to the N of 28n as
early as sunrise on Thu...and may reach as far S as 25n near
Bahia Santa Maria late Thu night mostly in refractive swell.
Wind/seas will begin to diminish/subside on Fri with winds 15 kt
and seas 5-7 ft across the subtropical waters on Sat.
The remnants of Alvin have weakened to SW-NE orientated trough
that extends from 10n130w to 15n126w. NE to E winds at 20-25 kt
and seas 7-10 ft are noted within 300 nm NW of the trough. Expect
the SW-NE orientated trough to drift W and extend from 09n133w
to 14n128w tonight...and from 09n136w to 11n133w to 13n128w on
Wed night...all the while interrupting the ITCZ. The NE trades
to the W of the trough will diminish to 15-20 kt tonight...with
the associated seas subsiding to less than 8 ft on Wed.
Aloft...a tropical moisture plume...originating from the
convective debris moisture from former tropical cyclone Alvin...
and other convection along the monsoon trough between 116w-
121w...concentrates into a 180 nm wide plume from 12n119w to
23n106w...then the plume continues NE across central Mexico and
across the W Gulf of Mexico where it evaporates with only a
small amount of the moisture indicated over se Texas this
morning. A second tropical plume originates from ITCZ convection
between 136w-148w and streams NNE within 300 nm of a line from
12n140w to 32n130w...with plume then widening as it spills NE
and later E across Southern California.