Dalila moved along the Pacific coast of Mexico for several days, but its center remained 100 n mi offshore. Dalila briefly reached hurricane strength. Some flash flooding in the province of Chiapas is attributed to Dalila's rainfall.
Dalila's origin is a tropical wave that moved westward from Africa and over the eastern tropical Atlantic Ocean on 10 July. It crossed northern South America and Central America on the 15th through 17th accompanied by vigorous thunderstorm activity, and then entered the Pacific basin on the 18th as an organized area of disturbed weather.
Early on the 21st, the system acquired a low-level circulation and became Tropical Depression Five-E, about 250 n mi south of the Gulf of Tehuantepec. Moving west-northwestward, it became Tropical Storm Dalila with 35-kt winds 12 hours later. The track of Dalila is plotted in Figure 1, and Table 1 lists the best track six-hour positions, maximum one-minute wind speed, and minimum central surface pressure.
Dalila's track was toward the west-northwest at forward speeds between 5 and 15 kt. The direction of motion was rather steady, varying between 285 and 300 degrees heading. This is attributed to a persistent subtropical ridge of high pressure located north of the cyclone. The center reached its point of closest approach to the coast of Mexico between Acapulco and Manzanillo on the 22nd and 23rd, when it came within about 100 n mi of the coast.
With warm sea surface temperatures and minimal vertical shear, the winds increased from 35 to 60 kt between the 22nd and 23rd. The wind speed briefly reached an estimated 65 kt on the 24th. Dalila was a hurricane for only a few hours and then remained at 55 kt until early on the 27th. The storm passed directly over Socorro Island on the 25th. By the 27th, most of the associated deep convection dissipated as the storm moved over colder water. Reduced to a swirl of low clouds, Dalila dissipated as a tropical cyclone on the 28th, while located about 650 n mi west of the southern tip of Baja California.
All of the observations used to track Dalila and to determine its wind speed and pressure were satellite-based. The observations are plotted in Figure 2 and Figure 3, which also show the best track wind and pressure curves.
The best track peak intensity of 65 kt at 1200 UTC on the 24th is plotted in Figure 2, and listed in Table 1. Dvorak intensity estimates during this time were as high as 77 kt. These estimates were based on night-time infrared images which showed a cold central dense overcast (CDO) clould pattern located over what was presumed to be an embedded center.
In contrast to the Dvorak technique, SSM/I and TRMM passes show a low-level center partially exposed to the northeast of the CDO, rather then embedded within. Visible images several hours later also do not support an embedded center. Intensity (pressure) estimates from the Advanced Microwave Sounding System (AMSU) (Not plotted in Figure 3) give a lowest pressure of 992 mb on the 25th.
An Associated Press report stated that heavy rains associated with Dalila caused flash flooding that damaged dozens of homes on the Chiapas coast.
Official track errors are very small, increasing from 30 n mi at 12 hours to 120 n mi at 72 hours for 11 cases. The average official 72-hour error is 185 n mi for the previous 10 years. Intensity errors range from 4 kt at 12 hours up to 17 knots at 48 hours, then decrease to 15 knots at 72 hours. These errors are also below the previous 10-year averages (18 kt at 48 hours and 21 kt at 72 hours).
Because of Dalila's rather close approach to the coast, the Government of Mexico issued various watches and warnings. These are listed in Table 2.
|Lat. (°N)||Lon. (°W)|
|21 / 0000||11.3||93.8||1007||30||tropical depression|
|21 / 0600||11.9||94.9||1006||30||"|
|21 / 1200||12.4||96.0||1004||35||tropical storm|
|21 / 1800||13.0||97.0||1001||40||"|
|22 / 0000||13.6||98.2||997||50||"|
|22 / 0600||14.2||99.4||994||55||"|
|22 / 1200||14.8||100.7||994||55||"|
|22 / 1800||15.5||102.1||994||55||"|
|23 / 0000||16.1||103.4||994||55||"|
|23 / 0600||16.7||104.5||994||55||"|
|23 / 1200||17.2||105.6||994||55||"|
|23 / 1800||17.5||106.4||994||55||"|
|24 / 0000||17.7||107.3||990||60||"|
|24 / 0600||18.0||108.1||988||60||"|
|24 / 1200||18.2||109.0||987||65||hurricane|
|24 / 1800||18.4||109.8||988||60||tropical storm|
|25 / 0000||18.6||110.5||989||60||"|
|25 / 0600||18.8||111.1||990||55||"|
|25 / 1200||19.0||111.6||990||55||"|
|25 / 1800||19.1||112.2||990||55||"|
|26 / 0000||19.3||112.8||990||55||"|
|26 / 0600||19.5||113.4||990||55||"|
|26 / 1200||19.7||114.0||990||55||"|
|26 / 1800||19.9||114.7||990||55||"|
|27 / 0000||20.1||115.5||990||55||"|
|27 / 0600||20.4||116.3||992||50||"|
|27 / 1200||20.7||117.1||994||45||"|
|27 / 1800||21.1||117.9||996||40||"|
|28 / 0000||21.5||118.9||999||35||"|
|28 / 0600||22.0||119.9||1003||30||tropical depression|
|28 / 1200||22.4||121.1||1007||25||"|
|28 / 1800||dissipated|
|24 / 1200||18.2||109.0||982||65||minimum pressure|
|21/1500||tropical storm watch||Puerto Angel to Acapulco|
|22/0300||tropical storm warning||Punta Maldonado to Lazaro Cardenas|
|22/0300||hurricane watch||west of Lazaro Cardenas to Manzanillo|
|22/0300||tropical storm watch discontinued||east of Punta Maldonado|
|22/0900||tropical storm warning and hurricane watch discontinued||Acapulco eastward|
|22/0900||tropical storm warning||extended from Punta Maldonado to Punta San Telmo|
|23/0300||all watches and warnings discontinued|
Figure 1: Best track map for Hurricane Dalila, 21-28 July 2001.
Figure 2: Best track maximum 1-min surface wind speed curve for Hurricane Dalila, 21-28 July 2001.
Figure 3: Best track minimum surface pressure curve for Hurricane Dalila, 21-28 July 2001.