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Tropical Cyclone Report

Tropical Storm Estelle

19 - 24 August 2004

Lixion A. Avila
National Hurricane Center
3 November 2004

a. Synoptic History

A tropical wave moved westward for a couple of weeks from Africa across the Atlantic, the Caribbean Sea and entered the eastern North Pacific with little convective activity. It was not until 18 August that the shower activity associated with the wave began to increase between 120°W and 130°W, as the wave interacted with a slow moving disturbance probably associated with the Intertropical Convergence zone (ITZC). The cloud pattern became organized and a few convective curved bands developed rather quickly. It is estimated that a tropical depression formed at 0600 UTC 19 August about 1250 n mi east-southeast of Hilo Hawaii. However, after the formation, there was no significant change in organization for the next 12 to 18 hours and in fact, some Dvorak estimates suggested weakening. Thereafter, convection redeveloped and T-numbers as well as data from a QuikSCAT pass indicated that the system had reached tropical storm status at 0600 UTC 20 August. Estelle moved toward the west-northwest around the periphery of the subtropical ridge and gradually strengthened. It then crossed 140°W into the area of responsibility of the Central Pacific Hurricane basin where Estelle reached its estimated maximum intensity of 60 knots and a minimum pressure of 989 mb at 1200 UTC 21 August. Thereafter, the cyclone began to move toward the west and west-southwest, and weakened due to strong shear. It became a remnant low devoid of thunderstorm activity at 1800 UTC 24 August and dissipated by 0000 UTC 26 August. The "best track" chart of the tropical cyclone's path is given in Figure 1, with the wind and pressure histories shown in Figure 2 and Figure 3, respectively. The best track positions and intensities are listed in Table 1.

b. Meteorological Statistics

Observations in Estelle (Figure 2 and Figure 3) include satellite-based Dvorak technique intensity estimates from the Tropical Analysis and Forecast Branch (TAFB), the Satellite Analysis Branch (SAB) and the U. S. Air Force Weather Agency (AFWA). Microwave satellite imagery from NOAA polar-orbiting satellites, the NASA Tropical Rainfall Measuring Mission (TRMM), the NASA QuikSCAT, and Defense Meteorological Satellite Program (DMSP) satellites were also useful in tracking Estelle.

c. Casualty and Damage Statistics

There were no reports of damage or casualties associated with Estelle.

d. Forecast and Warning Critique

The average official track errors (with the number of cases in parentheses) for Estelle were 36 (8), 60 (8), 83 (8), 131(8), 220(8), 229(6) and 329(2), n mi for the 12, 24, 36, 48, 72, 96, 120 h forecasts, respectively. These numbers are similar to the average official track errors for the 12, 24 and 36 h periods. However, they are larger than the average official track errors for the other forecast times. For comparison, the average official track errors for the 10-yr period 1994-2003 are 38, 70, 100, 127, 180, 210 and 247 n mi for the 12, 24, 36, 48, 72, 96, and 120 h periods, respectively.

Average official intensity errors were 4, 11, 13, 14, 21 24 and 30 kt for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively. The average official intensity errors over the 10-yr 1994-2003 period are 6, 11, 15, 17, 20, 18 and 19 kt, respectively.



Table 1: Best track for Tropical Storm Estelle, 19-24 August 2004.
Date/Time
(UTC)
PositionPressure
(mb)
Wind Speed
(kt)
Stage
Lat.
(°N)
Lon.
(°W)
 19 / 0600 11.6 131.8 1008 30 tropical depression
 19 / 1200 11.6 132.7 1008 30 "
 19 / 1800 12.0 134.0 1008 30 "
 20 / 0000 12.9 135.0 1007 30 "
 20 / 0600 13.6 136.3 1006 35 tropical storm
 20 / 1200 13.9 137.3 1005 35 "
 20 / 1800 14.0 138.3 1000 45 "
 21 / 0000 14.3 139.3 994 55 "
 21 / 0600 14.6 140.1 992 55 "
 21 / 1200 15.0 140.8 989 60 "
 21 / 1800 15.4 141.2 990 60 "
 22 / 0000 15.8 141.6 995 55 "
 22 / 0600 16.0 142.1 996 50 "
 22 / 1200 16.1 142.4 998 35 "
 22 / 1800 16.2 142.8 998 35 "
 23 / 0000 16.4 143.4 998 30 tropical depression
 23 / 0600 16.4 144.2 1002 30 "
 23 / 1200 16.3 145.1 1006 30 "
 23 / 1800 16.2 145.9 1008 30 "
 24 / 0000 16.0 147.0 1010 25 "
 24 / 0600 15.7 148.2 1012 25 "
 24 / 1200 15.3 149.2 1012 25 "
 24 / 1800 15.0 150.5 1012 20 remnant low
 25 / 0000 14.5 151.5 1012 20 "
 25 / 0600 14.3 152.5 1012 20 "
 25 / 1200 14.2 153.2 1012 20 "
 25 / 1800 14.0 154.0 1012 20 "
 26 / 0000     dissipated
 21 / 1200 15.0 140.8 989 60 minimum pressure

Best track positions for Tropical Storm Estelle

Figure 1: Best track positions for Tropical Storm Estelle, 19-24 August 2004. Best track information west of 140°W was provided by the Central Pacific Hurricane Center.

Selected wind observations and best track maximum sustained surface wind speed curve for Tropical Storm Estelle

Figure 2: Selected wind observations and best track maximum sustained surface wind speed curve for Tropical Storm Estelle, 19-24 August 2004. Best track information after 0000 UTC 21 August was provided by the Central Pacific Hurricane Center.

Selected pressure observations and best track minimum central pressure curve for Tropical Storm Estelle

Figure 3: Selected pressure observations and best track minimum central pressure curve for Tropical Storm Estelle, 19-24 August 2004. Best track information 0000 UTC 21 August was provided by the Central Pacific Hurricane Center.



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Page last modified: Tuesday, 15-Mar-2005 21:06:16 UTC