Tropical Cyclone Report

Tropical Storm Bertha

Bertha was a minimal tropical storm that made landfall in southeastern Louisiana.

a. Synoptic History

Bertha had a non-tropical origin, forming from the same non-tropical surface trough of low pressure that spawned Tropical Storm Cristobal in the western North Atlantic Ocean. This trough extended from the north central Gulf of Mexico across Florida into the Atlantic on 1 August and moved little for the next two days. A broad low pressure area was first noted on 3 August. Satellite, surface, and radar observations indicated the low became better organized just east of the mouth of the Mississippi River on 4 August, and the system developed into Tropical Depression Two around 1800 UTC that day. The "best track" of the tropical cyclone's path is shown 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 strengthened further as it moved west-northwestward. An Air Force Reserve Hurricane Hunter aircraft indicated the system became Tropical Storm Bertha near 2300 UTC 4 August. The broad center made landfall near Boothville, LA about two hours later. After landfall, Bertha assumed a wobbly northwestward motion that took the center to the north of Lake Ponchartrain later on the 5^th. The cyclone weakened back to a depression at 1200 UTC that day.

Bertha maintained its circulation over land while moving slowly westward and then southward on 6 August. It began a southwestward motion on the 7^th, which brought the center back to the Gulf of Mexico around 0900 UTC that day. This motion continued until late on 8 August. While satellite and radar data showed periods of increased organization, surface and aircraft observations showed only slight strengthening at most over the northwestern Gulf. The cyclone turned west-northwestward late on the 8^th, and this motion brought the center to the Texas coast east of Kingsville around 0800 UTC 9 August. Bertha weakened quickly after landfall and dissipated over southern Texas later that day.

b. Meteorological Statistics

Observations in Bertha (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), as well as flight-level observations from flights of the 53^rd Weather Reconnaissance Squadron of the U. S. Air Force Reserve Command.

Tropical Depression Two was upgraded to Tropical Storm Bertha on the basis of an aircraft report of 47 kt flight-level winds north of the center at 850 mb. The highest surface winds measured during the storm were at NOAA buoy 42007, which reported 33 kt 10-minute average winds at 2240 UTC 4 August and 0310 UTC 5 August. The buoy reported a peak gust of 43 kt at 0441 UTC on the 5^th. A nearby station run by Louisiana State University reported a 34 kt wind gust at 0000 UTC on the 5^th. The highest wind at a coastal site was a gust of 36 kt at an National Ocean Service station in Waveland, MS.

Storm tides reached as high as 3-4 ft -- 1-2 ft above normal tide levels -- along portions of the Mississippi and southeastern Louisiana coasts. Rainfall totals associated with Bertha were mainly in the 3-6 inch range. There were locally heavier amounts, including reports of 10.25 inches at Pascagoula, MS and Norwood, LA. No tornadoes were reported in association with Bertha.

Selected surface observations from land stations and data buoys are given in Table 2, while storm-total rainfalls are summarized in Table 3.

c. Casualty and Damage Statistics

Press reports indicate one death associated with Bertha - a drowning in high surf at Perdido Key State Park, FL on 4 August.

Rains associated with Bertha produced areas of stream and street flooding, which affected some structures producing minor damage. No monetary damage figures are available.

d. Forecast and Warning Critique

Bertha was a tropical storm for only 12 h, so no meaningful forecast verification statistics are available.

A tropical storm warning was issued at 2330 UTC 4 August for the northern Gulf coast from Pascagoula, MS to the mouth of the Mississippi River including Lake Borgne and Lake Ponchartrain. This warning was issued 1.5 h before landfall as Bertha reached tropical storm strength. The warning was discontinued at 1200 UTC 5 August as Bertha weakened to a depression over land.

Acknowledgments

The National Weather Service WFO in Slidell, LA provided the detailed rainfall data in this report.

Figure 1: Best track positions and minimum pressure for Tropical Storm Bertha, 4 - 9 August 2002.

Figure 2: Selected wind observations and best track maximum sustained surface wind speed curve for Tropical Storm Bertha, 4- 9 August 2002. Aircraft observations have been adjusted for elevation using an 80% reduction factor for observations from 850 mb.

Figure 3: Selected pressure observations and best track minimum central pressure curve for Tropical Storm Bertha, 4 - 9 August 2002.