Tropical Cyclone Report

Tropical Storm Georgette

Tropical Storm Georgette was a short-lived, west-northwestward-moving tropical cyclone that remained over the open northeastern Pacific Ocean.

a. Synoptic History

The tropical wave that eventually spawned Georgette moved across the west coast of Africa on 15 August. The wave moved westward across the tropical Atlantic Ocean with little associated shower activity until it reached the Gulf of Tehuantepec in the northeastern Pacific Ocean on 24 August. By early on 25 August, deep convection increased and became better organized, and a QuikSCAT overpass indicated a weak surface low pressure area had formed along the wave axis. Convection continued to increase during the day and Dvorak classifications were initiated on the system at 1800 UTC. Banding features improved significantly overnight and the cloud pattern was sufficiently well-organized to designate the system as a tropical depression at 1200 UTC 26 August, centered about 525 n mi south-southeast of the southern tip of Baja California. 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.

Deep convection continued to quickly organize and it is estimated that the tropical cyclone strengthened into Tropical Storm Georgette by around 1800 UTC 26 August. Georgette moved northwestward at 12-15 kt and, based on Dvorak satellite classifications and supplemental microwave satellite data (Figure 4), reached its peak intensity of 55 kt at about 1200 UTC 27 August. Shortly thereafter, upper-level northeasterly shear brought about a slow weakening trend while the cyclone was moving west-northwestward along the southern periphery of a strong subtropical high. Both the steering and shear patterns persisted for the next 3 days, and Georgette slowly weakened while it moved west-northwestward at 10-15 kt over cooler water. It is estimated that Georgette became a depression again by 0600 UTC 30 August about 770 n mi west of southern tip of Baja California. Weakening continued and the tropical cyclone quickly degenerated into a non-convective low pressure system by 1800 UTC that day. The remnant low remained devoid of significant convection as it moved west-northwestward over progressively colder water for the next 4 days. It finally dissipated early on 3 September about 520 n mi northeast of Hawaii.

b. Meteorological Statistics

Observations in Tropical Storm Georgette (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 imagery from NOAA polar-orbiting satellites, the NASA Tropical Rainfall Measuring Mission (TRMM), the NASA QuikSCAT program, and the Defense Meteorological Satellite Program (DMSP) was also useful in tracking Tropical Storm Georgette.

Georgette's peak intensity of 55 kt at 1200 UTC 27 August is estimated to have occurred approximately 6h before the highest Automated Objective Dvorak Technique (AODT) intensity estimate of 62 kt was observed (Figure 2). The lower intensity is based on subsequent DMSP microwave imagery (not shown) at 1645 UTC indicating that convection underneath the cold cloud canopy had actually weakened and had become much less organized than the AODT intensity estimate of 62 kt suggests. It is possible that the AODT algorithm was unable to distinguish between a cold CDO feature and a weaker Central Cold Cover (CCC) cloud pattern and/or placement of the low-level center was too far into the convective cloud canopy.

There were no reports of winds of tropical storm force associated with Georgette.

c. Casualty and Damage Statistics

There were no reports of damage or casualties associated with Tropical Storm Georgette.

d. Forecast and Warning Critique

Georgette was a tropical cyclone for only 96 h, resulting in a relatively small number of forecasts to verify. Average official track errors (with the number of cases in parentheses) for Georgette were 30 (15), 44 (13), 56 (11), 58 (9), 41 (5) n mi for the 12, 24, 36, 48, 72 h forecasts, respectively. These errors are much lower than the average official track errors for the 10-yr period 1994-2003^[1] of 38, 70, 100, 127, and 180 n mi, respectively (Table 2).

Average official intensity errors were 6, 10, 12, 12, and 20 kt for the 12, 24, 36, 48, and 72 h forecasts, respectively. These errors are comparable to the average official intensity errors over the 10-yr period 1994-2003 of 6, 11, 15, 17, and 20 kt, respectively.

No watches or warnings were associated with Georgette.

^[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 Tropical Storm Georgette, 26-30 August 2004.

Figure 2: Selected wind observations and best track maximum sustained surface wind speed curve for Tropical Storm Georgette, 26-30 August 2004. Objective Dvorak estimates represent linear averages over a three-hour period centered on the nominal observation time.

Figure 3: Selected pressure observations and best track minimum central pressure curve for Tropical Storm Georgette, 26-30 August 2004. Objective Dvorak estimates represent linear averages over a three-hour period centered on the nominal observation time.

Figure 4: 0902 UTC 27 August 2004 AMSR-E AQUA-1 overpass with composite images showing the tight circulation of Tropical Storm Georgette near its peak intensity of 55 kt (image courtesy of the Naval Research Laboratory, Monterey, CA).