a. Synoptic History
The tropical storm
formed about 800 miles to the south of the southern tip of Baja California,
likely from a tropical wave
analyzed to have crossed Central America and northern South America
on 8 May. The associated thunderstorm activity was limited and sporadic
until early on the 13th when it expanded and became more persistent.
A band of deep convection developed on the northwest side of the system that morning.
Dvorak T-numbers from the
Synoptic Analysis Branch (SAB)
and the TPC Tropical Analysis and Forecast Branch
(TAFB) reached 1.5 at 0600 UTC and then 2.0 at 1130 UTC that day. Based on those analyses,
it is estimated that the system became a tropical depression
at 0600 UTC on the 13th (Fig. 1
[19K GIF] and Table 1).
The cyclone moved toward the
west-northwest at about 10 knots during its three-day existence and did not affect land.
There is uncertainty about the maximum intensity reached by this
Operational estimates of 30 knots were based on application of the Dvorak technique.
Those analyses of satellite pictures showed little variation, ranging from 30 knots by the
Air Force Global Weather Central
(AFGWC) and the TAFB, to 35 knots
by the SAB. These maxima were generally centered on the early hours
of 14 May, when a small core of deep convection developed in an
environment with a southerly component of vertical wind shear. Subsequently, the
U.S. Coast Guard
relayed reports to the National Hurricane Center from the vessel Solar Wind
suggesting that the cyclone had maximum winds of tropical storm strength on the 14th.
Deep convection near the circulation
became spotty by late on the 14th and then disappeared completely
on the night of the 15th-16th. The system dissipated on the 16th.
b. Meteorological Statistics
Figures 2 (22K GIF)
(23K GIF) show the tropical storm's estimated central
pressure and maximum one-minute wind speed, respectively, versus
time and the associated satellite and ship intensity data.
Position and intensity estimates from satellite pictures were provided by the
TAFB and SAB.
The Coast Guard
reported that at least two vessels, including the 37-ft trimaran Solar Wind
and the True Blue were affected by the
cyclone. Analysis of satellite pictures early on the 14th
suggests that the Solar Wind was located in the general vicinity of
an isolated thunderstorm cluster seen just north of the circulation center.
The Solar Wind observed a wind speed of 35-42 knots
for an unspecified period near 0400 UTC on the 14th and the anemometer
showed its maximum capability, 60 knots, for an
unknown duration near 0600 UTC. The 0400 UTC report from that ship also included an
observation of 4-6 ft seas, which would be generally consistent
with either localized, transitory winds of the magnitude reported
or lower wind speeds than noted. The True Blue was located about
50 miles to the north of the Solar Wind during this period and
reported winds of 20 knots. The maximum one-minute wind speed for
this storm is now estimated to have been 45 knots
at 0600 UTC on the 14th.
c. Casualty and Damage Statistics
Communications with the Solar Wind were lost after 0600 UTC on the
14th. The Coast Guard
began, but later suspended, a search for the vessel and its two-man crew.
The fate of the crew remains unknown.
d. Forecast and Warning Critique
The tropical cyclone was of tropical storm strength for too short
a period to obtain a meaningful quantitative evaluation of forecast
The observations and analyses of this tropical cyclone serve as
reminders of the large uncertainty often associated with tropical
cyclone intensity estimates. They also call attention to the great
importance and scarcity of reliable surface weather observations in
the vicinity of tropical cyclones. Such limitations diminish the
accuracy and reliability of warnings.