Hurricane and Tropical Cyclones


Tropical Weather Discussion

axpz20 knhc 280338

Tropical weather discussion                                    
NWS National Hurricane Center Miami FL                         
0405 UTC Tue Apr 28 2015

Tropical weather discussion for the eastern Pacific Ocean from  
the Equator to 32n...east of 140w. The following information is 
based on satellite observations...radar...and 
meteorological analysis.

Based on 0000 UTC surface analysis and satellite imagery through 
0215 UTC. 

...Special features...

Gulf of Tehuantepec Gale Warning...model guidance is in good 
agreement regarding weak low pres developing se of Tehuantepec 
likely induced by mid/upper level dynamics approaching the area. 
Along with high pres building over NE Mexico in the wake of a 
Gulf of Mexico cold front...this will tighten the pres gradient 
and support gale conditions through the Gulf of Tehuantepec by 
Wed afternoon continuing into early Thu morning. Seas will build 
to up to 12 to 13 ft during the gale force winds by late Wed 

...Intertropical convergence zone/monsoon trough...              

The monsoon trough axis extends from 10n100w to low pres     
near 08n117w then continues as the ITCZ from the low to 06n140w. 
Widely scattered moderate convection is from 07n to 09n between 
91w and 100w. Scattered moderate and isolated strong convection 
is within an area bounded by a line from 16n108w to 05n100w to 
04n116w to 16n108w. Scattered moderate convection is within 180 
nm in the N and se quadrants of the low...and also within 150 nm 
N of the axis between 122w and 127w.


E of 120w...

Troughing aloft and an associated upper low moving across New 
Mexico into W Texas is supporting relatively low pres over NW 
Mexico including Baja California norte. This pres pattern has 
relaxed since yesterday when gale force winds were occurring 
however some residual northerly swell persists with seas to 8 ft 
reaching as far south as 24n off baja. Various wave model 
guidance remains in good agreement showing these seas   
subsiding to less than 8 ft overnight.

Farther south...the tropical epac is starting to transition to 
its late Spring/Summer pattern...with significant mid latitude 
influences. What was a coherent ITCZ is breaking down into a 
large area of east to west oriented troughing along roughly 
10n...although with fairly weak and inconsistent southerly flow. 
A mid/upper level short wave trough is evident on water vapor 
imagery approaching from the NW...providing support to a large 
area of moderate to strong convection around a 1008 mb surface 
low centered near 08n117w. Guidance indicates this low pres will 
weaken and dissipate through 48 to 72 hours as it drifts W...and 
as the supporting upper dynamics shift east. 

Seas are generally 4 to 6 ft over the tropical epac with little 
change expected until later in the week when long period SW 
swell with wave heights of 8 to 10 ft moves across the Equator 
in the waters W of the galapagos.

W of 120w...

A split flow pattern is noted aloft ahead of sharp upper 
troughing approaching from the NW. The trough will shift 
eastward to the north of 25n...weakening the deep layer ridging 
ahead of it to include a weakening 1020 mb high pres area 
centered near 31n134w. This in turn will allow persistent fresh 
trade wind flow farther south to diminish by Tue afternoon. 
However the subtropical ridge builds eastward from the central 
Pacific tonight behind the trough. Persistent trade wind flow 
along with components of NW swell are contributing to 8 to 10 ft 
seas noted in earlier altimeter imagery...covering an area from 
08n to 16n W of 124w. These seas will subside in heights and 
coverage through 48 hours as the trade wind flow diminishes. 
Wave guidance indicates long period NW swell will move into the 
NW corner of the area by Tue morning propagating to the se 
through Wed with seas of 8 to 11 ft.


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