Hurricane Dolly formed from a tropical wave
of large lateral extent that moved from the west coast of Africa to the central
Caribbean Sea during 9-18 August 1996. Although the wave generated
deep convection when it emerged from Africa, there was little
accompanying thunderstorm activity for much of its passage across
the tropical North Atlantic Ocean. Deep convection redeveloped
when the wave reached the eastern Caribbean, but did not persist in
a concentrated pattern until the system was south to southwest of
Jamaica on the 18th-19th. A low- to mid-level cyclonic circulation
was then detected in data obtained during a NOAA research flight
to study the development of tropical cyclones. Satellite analysts indicated
that the system was too weak to classify using the Dvorak technique late
on the 18th, but they calculated Dvorak T-numbers of 1.5 and 2.0 on the afternoon
of the 19th. By mid-afternoon on the 19th, the first center "fix" by
reconnaissance aircraft was made and data from the plane, satellite, and a
ship
that reported 45 knots at 1800 UTC were used to estimate that the tropical
depression stage began with a poorly-defined circulation center near 0600 UTC
on the 19th, and that the depression became Tropical Storm Dolly a little
more than six hours later.
The tropical cyclone developed near or just south of a mid- to
upper-level anticyclone. In that environment, Dolly strengthened
on the 19th and 20th and moved toward the west-northwest at a speed that
decreased from 15 knots to about 8 knots.
Convection became better organized near the circulation center on
the 20th and, just before making landfall on the Yucatan peninsula
to the northeast of Chetumal, Dolly became a hurricane.
It weakened back to a tropical depression and slowed to about 5 knots
during its 24-hour passage over the peninsula, and satellite
pictures showed the center of cloud rotation displaced to the south
of the estimated surface circulation center.
Gradual restrengthening began a few hours after the surface center
arrived over the Bay of Campeche. Dolly regained hurricane status
and was at it strongest, with 70 knot winds and a central pressure
of 989 mb, when it accelerated to 15 knots and made its final
landfall about midway between Tuxpan and Tampico near 1800 UTC on
the 23rd.
Dolly then weakened and, as a tropical depression, crossed central
Mexico. It continued to generate areas of deep convection and,
likely, heavy precipitation even while its surface center dissipated over the
eastern North Pacific Ocean on the 25th.
The only available official observations of at least tropical storm
force winds from a surface land site came from Tampico, Mexico.
There, 10-minute winds of 40 knots with gusts to 60 knots occurred
at 1045 UTC and 1145 UTC on the 23rd. An amateur radio report of
a gust to 59 knots was received from Tampico.
The three largest 24-hour rainfall totals reported to the
meteorological service of Mexico came from Micos (12.94 inches),
Santa Rosa (10.59 inches), and Puerto de Valles (10.00 inches).
The rains, which in some cases were heavier on Mexico's west coast
than its east coast, also occurred in the more widely-known cities
of Acapulco (7.48 inches), Los Mochis (7.06), Tuxpan (5.88 inches),
Chetumal (5.73 inches), Monterrey (4.93 inches), and Cancun (1.35 inches).
According to newspapers reports, Hurricane Dolly was responsible
for fourteen deaths in Mexico--including six in Veracruz (all
drowned), three in Nuevo Leon, and one each in Pueblo Viejo and
Monterrey. Two people were missing in Nuevo Leon.
Those reports also indicated hundreds of residences destroyed and
35,000 people displaced. Severe damage occurred in Tuxpan,
Tamiahua, Pueblo Viejo, Platon, Panuco, Tampico Alto and elsewhere
along the coast of northeast Mexico. A river overflowed its banks
causing damage in Pueblo Viejo. A large area of farm land was lost
to flooding in Quintana Roo on the Yucatan peninsula.
Rain prompted evacuations in the southern part of the state of San
Luis Potosi. About 6500 people were evacuated from low-lying zones
of Tampico.
Widespread communication and power outages were noted as far
west as Mazatlan.