Tropical Weather Discussion

axpz20 knhc 222208

Tropical weather discussion  
NWS National Hurricane Center Miami FL
2205 UTC Mon Oct 22 2018  

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 
2100 UTC.      

...Special features... 

Dangerous Hurricane Willa is centered near 19.7n 107.2w at 2100 
UTC moving N at 7 kt. Estimated minimum central pressure is 929 
mb. Maximum sustained wind speed is 140 kt with gusts to 170 kt. 
Willa has ingested some dry air into its core today which has 
disrupted the intensification, and produced a reorganization of 
the eyewall. Numerous strong convection continues within 90 nm 
across the N and 120 nm across the S semicircles, with scattered 
moderate to strong convection in bands elsewhere within 150 nm 
of the center except 240 nm across the se quadrant. These rain 
bands on the eastern side of Willa will bring very heavy 
rainfall along the Pacific coast of Mainland Mexico from 
michoacan to southern sinaloa during the next 48 hours. Willa is 
expected to continue northward this evening, then begin to 
gradually veer NE and across las Tres Marias before sunrise 
early Tue, then accelerate and move inland to the south of 
Mazatlan in southern sinaloa early Tue evening. Large swells 
generated by Willa will continue to reach the Mainland Mexican 
coast between 100w and 108w through tonight, and into the 
southern third of the Gulf of California. These swells will 
produce very large and powerful surf and cause life-threatening 
rip current conditions. Please refer to local forecasts from the 
meteorological service of Mexico for specific information on 
heavy rainfall and flash flood potential from Willa. Refer to 
the latest NHC forecast/advisory under AWIPS/WMO headers 
miatcmep4/wtpz24 knhc for additional details. 

Tropical Storm Vicente centered near 15.4n 101.5w at 2100 UTC 
moving WNW at 10 kt. Estimated minimum central pressure is 1005 
mb. Maximum sustained wind speed is 35 kt with gusts to 45 kt. 
Scattered moderate to strong convection is occurring in bands 
within 120 nm N and 150 nm across the S semicircles. Vicente 
will continue on a general WNW track through the southern 
Mexican offshore waters into this evening then turn more NW and 
gradually weaken to a tropical depression through Tue afternoon 
as it approaches the Mexican coast near Manzanillo. Rainfall 
produced from Vicente as it moves ashore late Tue will move over 
areas already dumped on by heavy rain from Willa and may further 
compound flooding conditions. Refer to the latest NHC forecast/ 
advisory under AWIPS/WMO headers miatcmep3/wtpz23 knhc for 
additional details.  

...Tropical wave...

A tropical wave is analyzed N of 06n along 90w-91w. Scattered 
moderate to strong convection continues along the monsoon trough 
associated with the wave.

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

The monsoon trough extends W off the Caribbean coast of Colombia 
westward across Costa Rica near 09.5n84w to 08.5n94w to 12n97w, 
where it breaks, then resumes SW of Hurricane Willa near 14n111w 
to surface low near 11.5n116.5w to 09.5n124w, where it 
transitions to ITCZ and continues on to beyond 10.5n140w. Widely 
scattered moderate isolated strong convection is observed within 
60 nm N and 180 nm S of the trough and ITCZ west of 111w.


Offshore waters within 250 nm of Mexico... 

See the special features paragraph for details on tropical 
cyclones Vicente and Willa.  

W of the Baja California peninsula...gentle to locally moderate 
NW to N flow is expected through this evening when the pressure 
gradient will tighten, supporting moderate to locally fresh 
northerly flow W of the Baja California peninsula on Tue into 
early Wed as Willa moves NE across las Tres Marias and inland 
across southern sinaloa. Large southerly swell from Hurricane 
Willa will propagate N through the waters W of baja beginning 
this evening, and reaching as far N as 28n early Wed, before 
beginning to subside. 

Gulf of california: light, mostly northerly flow is expected 
across the northern two-thirds of the Gulf through this 
afternoon when large southerly swell from Willa will propagate 
into the southern Gulf waters, and then persist through late Tue 
night. Fresh to locally strong northerly winds are also expected 
across the Gulf waters S of 24.5n late this afternoon into Wed 
as Willa passes just S of the Gulf entrance. 

Gulf of Tehuantepec...fresh to locally strong northerly flow is 
expected through late this morning.  

Offshore waters within 250 nm of Central America, Colombia, and 
within 750 nm of Ecuador...

Gulf of papagayo...pulses of fresh N to NE flow are forecast 
through Tue morning.  

Light northerly winds and 4 to 7 ft seas are forecast elsewhere 
N of the monsoon trough, while moderate to locally fresh 
southwesterly monsoonal flow, with 5 to 8 ft seas forecast 
through this afternoon, then mostly moderate SW flow and 4 to 7 
ft seas are forecast through the middle of the week.

Remainder of the area...   

Refer to the special features paragraph above for details on 
tropical cyclone Willa.

A 1008 mb low near 11.5n116.5w will drift W for the next several 
days with fresh southerly flow, and 6 to 8 ft seas forecast 
within 300 nm se of the low. This low has a low chance of 
becoming a tropical cyclone during the 5 days. 

A surface high will meander near 28n136w with moderate to 
locally fresh anticyclonic flow forecast across the tropical 
waters N of the monsoon trough and ITCZ, and W of 122w through 
the middle of the week. An area of 7 to 9 ft seas is observed 
across the tropical waters from 12n to 17n W of 128w. These 
conditions will gradually shrink in areal coverage and shift W 
through Wed morning.



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