Hernan made landfall on the coast of Mexico, between Manzanillo and Puerto Vallarta,
as a category one hurricane on the
Saffir/Simpson Hurricane Scale.
a. Synoptic History
A tropical wave
that emerged from the coast of western Africa in mid-September moved westward
across the Atlantic basin during the latter half of the month. Convection associated
with the system temporarily increased near the Lesser Antilles on 22 September,
and again on 25-27 September, as the wave moved across the western Caribbean Sea
and Central America. Deep convection associated with the wave became a little more
consolidated near the Gulf of Tehuantepec on the 28th. By 1800 UTC on the 29th, when
the wave axis was near 97W, the cloud pattern was sufficiently well-organized that
Dvorak classifications on the system were being given by the
Tropical Analysis and Forecast Branch (TAFB). Satellite data
indicate that Tropical Depression
Eleven-E developed from this disturbance a little over 250 n mi
south-southeast of Acapulco around 0600 UTC 30 September, as shown in
Table 1, the post-analysis
"best track". Gradual development continued,
and the cyclone became
Tropical Storm Hernan about 12 hours later.
Initially, the cyclone was moving westward, but the motion soon became
west-northwestward and then northwestward. Early on October 1, Hernan shifted
northward, and then north-northeastward. The storm was still in the developing stage
and not yet well-organized; thus, part of this displacement was probably related to a
reformation of the center.
Later on the 1st, Hernan, then better-organized, turned back
toward the north-northwest and, on the 2nd, toward the northwest. By 0600 on the
2nd, when the center was nearing the coast and located about 60 n mi south of Lazaro
Cardenas, Hernan strengthened into a hurricane. Reflectivity presentations from the
Mexican weather service radar located at Cuyutlan (central coast of the State of
Colima), at around 1000 UTC on the 2nd, revealed a well-defined, closed eyewall. The
maximum intensity of Hernan, 75 knots,
is estimated to have occurred around that time.
From 1200 UTC on the 2nd through 0000 UTC on the 3rd, the hurricane moved
parallel, but very near, to the coastline. Early on the 3rd, the forward motion slowed
to a crawl and the center moved in a small counter-clockwise loop, just offshore.
Hernan then responded to a mid- to upper-tropospheric trough over the southwestern
United States and moved northward, making landfall near Barra de Navidad, at 1000
UTC 3 October. Since the center had been moving very near to the mountainous
landmass of Mexico for about 24 hours prior to landfall, the hurricane had weakened
somewhat before the center finally crossed the coast. Hernan weakened to a tropical
storm just after landfall. The cyclone moved mostly northward over land, passing just
east of Puerto Vallarta while weakening below storm strength by 0000 UTC on the 4th.
Although the center briefly moved back out over the waters north of Puerto Vallarta,
the system had become so disorganized that it dissipated around 0000 UTC 5 October.
Figure 1 (25K GIF) depicts
the best track of Hernan.
b. Meteorological Statistics
Figures 2 (24K GIF)
and 3 (27K GIF)
are the curves of minimum central sea-level pressure and maximum
one-minute average "surface" (10 meters above ground level) wind speed, respectively,
as functions of time. Also plotted are the observations on which the curves are based,
consisting of Dvorak-technique estimates (from the TAFB, the
Synoptic Analysis Branch, and the U.S.
Air Force Global Weather Center)
using satellite imagery.
There were three ship reports of tropical storm force winds associated with Hernan.
The first, at 0600 UTC 1 October, a vessel with unknown call sign, location 15.2°N
100.2°W, wind 090/35 knots, pressure 1008.3 mb. The second, at 1200 UTC 1
October, call sign KLHZ, location 14.7°N 97.1°W, wind
150/35 knots, pressure 1007.8 mb. The third, at 1800 UTC 1 October,
call sign MQWA5, location 15.4°N 100.7°W, wind 160/40 knots,
pressure 999.1 mb.
No actual measurements of strong winds from land have been received. Local press
reports indicate that waves along the coasts of the states of Colima and Jalisco reached
c. Casualty and Damage Statistics
Hernan struck a relatively sparsely-populated area of Mexico. Local press reported
at least 100 injuries with 1,000 homes damaged. There was flooding in the coastal
town of Melaque, Jalisco. Washouts were reported on Mexico Route 200, the coastal
road between Puerto Vallarta and Manzanillo, and on Mexico Route 80, which runs
between Melaque and Guadalajara. Telephone service and electricity were disrupted
in various locations.
d. Forecast and Warning Critique
Table 2 is a listing of track forecast error statistics for
Hernan. Although, the sample size is very small, one can see that the official and model forecasts
were generally larger than the NHC's long-term averages for the eastern Pacific. This is
typically the case for landfalling storms in that basin. Hernan was correctly forecast
to become a hurricane. However, in most cases, the intensity of this
was somewhat underforecast in the NHC advisories.
A tropical storm warning
was issued for Mexico from Acapulco to Manzanillo at 1800 UTC 1 October. A
was put into effect from Zihuatanejo to Manzanillo at 0300 UTC 2 October. This was changed to a
hurricane warning at
0900 UTC 2 October. A tropical storm warning was issued north of Manzanillo to San
Blas at 1500 UTC 2 October, and the hurricane warning was extended north of
Manzanillo to Cabo Corrientes at 2100 UTC 2 October. Hurricane warnings were
extended north of Cabo Corrientes to San Blas and tropical storm warnings were
extended north of San Blas to Mazatlan at 0300 UTC 3 October. There was a
relatively short lead time, roughly six hours, between the issuance of hurricane
warnings and the arrival of the eyewall
(not the center) on the coast on 2 October. Hernan's center ultimately crossed
the coast (on 3 October) about 13 hours after the issuance of hurricane warnings
for the landfall area.