Octave was a hurricane far from land over the eastern Pacific basin with winds reaching 75 knots.
Octave originated in the intertropical convergence zone and its development was likely initiated by a weak tropical wave that had moved westward across Central America on 22 October. By the 27th, convection had increased over a large area between 95 - 115 degrees west longitude and between 8 - 15 degrees north latitude. A low-level circulation gradually developed within this area and became a tropical depression on the 31st while centered about 1000 n mi southwest of the southern tip of Baja California. The "best track"of the tropical cyclone begins at 0000 UTC on the 31st. A map of the best track positions is shown in Figure 1 and six-hour center positions, wind speeds, and central pressures are listed in Table 1. Time series curves of best track wind speed and pressure are shown in Figure 2 and Figure 3.
The cyclone started out to the south of a mid-layer ridge, but a weakness soon developed in this ridge from a trough approaching from the west. This resulted in a general northwestward track. More specifically, the cyclone moved toward the west-northwest on the 31st, followed by a turn toward the north-northwest on the 1st. On the 3rd, low-level steering turned it back toward the west-northwest.
Under light vertical shear for 48 hours, the depression gradually strengthened to a 75 knot hurricane by 1 November, with a ragged eye visible for a few hours on satellite images. Vertical shear began increasing on the 1st and reached 30-35 knots on the 3rd. During this period, Octave weakened from a 75-knot hurricane to a dissipating swirl of low clouds on the 3rd, located about 1300 n mi west-southwest of the southern tip of Baja California.
Satellite images were the primary data source to estimate the maximum 1-minute surface wind speed and minimum central surface pressure. The satellite intensity estimates are plotted in Figure 2 and Figure 3.
No deaths or damages are attributed to Octave.
The official track forecast errors were 11, 25, 40, 46, 64, and 192 n mi, respectively for the 0-, 12-, 24-, 36-, 48-, and 72-hour forecasts. The number of cases ranged from 13 at 0 hours to only one case at 72 hours. These errors are considerably smaller than the previous official ten-year averages at 12 through 48 hours and about the same as the previous averages at 0 and 72 hours. The official wind speed errors were 1, 7, 9, 12, 15, and 5 knots for the 0-, 12-, 24-, 36-, 48-, and 72-hour forecasts. These errors are all smaller than the previous ten-year average official errors.
|Lat. (°N)||Lon. (°W)|
|31 /0000||12.1||122.8||1007||30||tropical depression|
|31 /0600||12.5||123.9||1005||35||tropical storm|
|04/0000||low cloud swirl|
Figure 1: Best track positions for Hurricane Octave, 31 October - 3 November 2001.
Figure 2: Best track maximum sustained surface wind speed curve for Hurricane Octave, 31 October - 3 November 2001, and the observations on which it is based.
Figure 3: Best track minimum central pressure curve for Hurricane Octave, 31 October - 3 November 2001, and the observations on which it is based.