a. Synoptic History
The origin of Tropical Storm
Dalila* can be traced to a
tropical wave that moved westward
from Africa to the tropical Atlantic Ocean on 11 July. The wave soon developed two areas of
thunderstorm activity. One of these moved northwestward and showed signs of becoming a
tropical depression before degenerating
over the eastern Atlantic. The other, farther south, moved westward across the Atlantic Ocean
and then the Caribbean Sea and Central America from the 11th through the 21st.
Thunderstorms associated with the wave became more concentrated several hundred miles to
the southwest of the Gulf of Tehuantepec on the 23rd. Based on satellite pictures and surface
analyses it is estimated that this system became a tropical depression at 1200 UTC the next day
(Table 1 and Fig. 1
[40K GIF]). The cyclone was then in an environment of weak
steering currents and, over the course of the following three days, moved slowly first toward
the north-northeast and then toward the northwest. The low-level circulation was not
strongly convergent, with satellite pictures and surface data indicating a fairly broad area of
west-southwesterly winds to the south and southeast of the depression. Easterly shear displaced
the deepest convection up to 60 n mi to the west of the low-level cloud
center. Only slight strengthening occurred and although the
cyclone became a tropical storm on the 25th, it still had only 35 knot
winds late on the 27th.
A deep-layer anticyclone then developed to the north of the storm. Dalila accelerated to 12
knots, initially heading toward the west-northwest and then the northwest. The shear decreased
and the storm reached its peak intensity of 55 knots on the 28th.
Dalila weakened upon moving over cooler water southwest of the Baja California peninsula.
It stopped generating deep convection late on the 31st and dissipated on 2 August.
b. Meteorological Statistics
Figures 2 (24K GIF) and
3 (25K GIF) show "best track"
curves of estimated minimum central pressure and maximum one-minute
wind speed versus time, respectively, and the data upon which they were based. The
Air Force Global Weather Center (AFGWC),
the NHC Tropical Analysis and Forecast Branch (TAFB; TSAF in figures), and
Synoptic Analysis Branch (SAB)
supplied the Dvorak technique classifications.
There were no surface reports of tropical storm force winds related to Dalila.
A measure of the uncertainty of Dalila's early intensity estimates is given by comparing the
0000 UTC 27 July satellite classifications from the AFGWC--which stated that the system had
dissipated--and the analyses of the TAFB and SAB--which had Dalila as a tropical storm.
c. Casualty and Damage Statistics
There were no casualties or damages reported in association with Dalila.
d. Forecast and Warning Critique
The magnitudes of official track forecast errors were, on average, comparable to the past
averages and smaller than most of the objective guidance errors for this storm. Intensity forecast
errors were also similar in size to past averages.
Watches and warnings were neither issued nor necessary.
* The name "Dalilia" (Spanish for Delilah) was used in 1981 and
1988 and changed, perhaps inadvertently, to Dalila in operational documents prior to the 1995