Tropical Cyclone Report

Hurricane Howard

Howard was a category 4 hurricane on the Saffir-Simpson Hurricane Scale over the eastern North Pacific Ocean west of the coast of Mexico.

a. Synoptic History

Howard formed from a tropical wave that moved westward across the coast of Africa on 18 August. While there was no development as the wave crossed the Atlantic, an increase in the associated shower activity occurred on 26 August when the system reached the western Caribbean and the eastern North Pacific. The wave then moved west-northwestward parallel to the coast of Central America and Mexico. Shower activity increased in both coverage and organization on 29 August, and continued development resulted in the formation of a tropical depression around 1200 UTC 30 August about 350 n mi south-southwest of Acapulco, Mexico. 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.

The depression moved west-northwestward on the southwest side of a mid-level ridge over Mexico and strengthened. It became a tropical storm early on 31 August and a hurricane on 1 September. Howard then strengthened rapidly and reached an estimated peak intensity of 120 kt on 2 September. This was followed by weakening as Howard moved northwestward over decreasing sea surface temperatures. Howard weakened to a tropical storm on 4 September and a tropical depression early on 5 September. The cyclone became a non-convective remnant low later that day about 230 n mi west-southwest of Punta Eugenia, Mexico.

The remnant low continued slowly northwestward until 6 September when it turned southwestward on the south east side of a low-level ridge. A general southwestward motion would continue until 10 September, when the low finally dissipated about 1000 n mi west-southwest of Cabo San Lucas, Mexico.

b. Meteorological Statistics

Observations in Howard (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 Aqua, the NASA QuikSCAT, and Defense Meteorological Satellite Program (DMSP) satellites were also useful in tracking Howard.

The only surface observation of tropical storm winds in Howard was from the ship Strong Virginian (call sign KSPH), which reported winds of 37 kt at 0600 UTC 4 September.

c. Casualty and Damage Statistics

There were no reports of damages or casualties associated with Howard.

d. Forecast and Warning Critique

Average official track errors (with the number of cases in parentheses) for Howard were 32 (22), 46 (20), 65 (18), 88 (16), 123 (12), 184 (8), and 193 (4) n mi for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively. These errors are lower than the average official track errors for the 10-yr period 1994-2003^[1] (38, 70, 100, 127, 180, 210, and 247 n mi, respectively), (Table 2). However, several of the track guidance models had lower average errors than the official forecast, most notably the GFDL and GUNS, which were better than the official forecast at all times. These models more accurately forecasted the northwestward motion of Howard early in its life while the official forecasts called for a west-northwesterly motion - a left bias - during that time.

Average official intensity errors were 9, 16, 20, 24, 27, 19 and 13 kt for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively. For comparison, the average official intensity errors over the 10-yr period 1994-2003 are 6, 11, 15, 17, 20, 18, and 19 kt, respectively. The mostly larger than average intensity errors resulted from a combination of underforecasting how strong Howard would get early in its lifetime and overforecasting how strong it would remain later in its life.

Watches and warnings were not necessary for Howard.

^[1]Errors given for the 96 and 120 h periods are averages over the three-year period 2001-3.

Figure 1: Best track positions for Hurricane Howard, 30 August - 5 September 2004.

Figure 2: Selected wind observations and best track maximum sustained surface wind speed curve for Hurricane Howard, 30 August - 5 September 2004.

Figure 3: Selected pressure observations and best track minimum central pressure curve for Hurricane Howard, 30 August - 5 September 2004.