Miriam was a minimal tropical storm that briefly threatened the southern Baja California peninsula of Mexico before weakening to a tropical depression.
a. Synoptic History
The antecedent disturbance to Miriam was a weak tropical wave that crossed the coast of Africa on 29 August. The wave briefly developed some rotational character in the south-central tropical Atlantic on 2 September, but then continued to the west without distinction across South America and emerged into the eastern North Pacific on the 9th. Westward progression of the wave slowed over the next several days as it moved into a broad area of low pressure south and southwest of the Gulf of Tehuantepec, and began to take a more northwesterly track. Dvorak technique classifications on the disturbance that was to become Miriam began at 0600 UTC on the 15th, although a separate disturbance in the vicinity had been previously classified for several days. During the day, the system developed short banding features and by 1800 UTC on the 15th, ship reports indicated a closed circulation had developed and that a tropical depression had formed about 250 n mi south-southeast of Cabo San Lucas, 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 is listed in Table 1.
Over the next 24 hours, the depression moved to the north then north-northwest with only intermittent organized convection. The system became a tropical storm at 1200 UTC on the 16th, when it was about 175 n mi southeast of Cabo San Lucas, but weakened within twelve hours to a depression in southwesterly shear. The depression continued to the north-northwest into the southern Gulf of California, where the circulation dissipated shortly after 1200 UTC on the 17th, when it was about 60 n mi northeast of Cabo San Lucas.
b. Meteorological Statistics
Observations in Miriam (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). Although these estimates support tropical storm strength for 24 hours or longer, scatterometer data from the QuikSCAT satellite suggest that this interval was no longer than twelve hours, and it is conceivable that Miriam never truly was a tropical storm.
There were no ship or land-based reports of winds of tropical storm force associated with Miriam.
c. Casualty and Damage Statistics
There were no reports of damage or casualties associated with Miriam.
d. Forecast and Warning Critique
Miriam was a tropical storm for less than 12 hours, so there are no verifying forecasts. A tropical storm warning (Table 2) was issued by the government of Mexico for a portion of the southern Baja California peninsula, but Miriam weakened to a tropical depression before reaching the area. The tropical storm warning remained in effect until 1500 UTC on the 17th because Miriam was carried operationally as a tropical storm until that time.
Table 1. Best track for Tropical Storm Miriam, 15-17 September 2000. Date/Time
(UTC)Position Pressure
(mb)Wind Speed
(kt)Stage Lat. (°N) Lon. (°W) 15 / 1800 19.2 107.4 1005 30 tropical depression 16 / 0000 19.8 107.4 1005 30 " 16 / 0600 20.2 107.6 1005 30 " 16 / 1200 20.6 107.8 1004 35 tropical storm 16 / 1800 21.0 108.2 1004 35 " 17 / 0000 21.5 108.5 1004 30 tropical depression 17 / 0600 22.4 108.9 1005 25 " 17 / 1200 23.7 109.2 1005 25 " 17 / 1800 dissipated 16 / 1200 20.6 107.8 1004 35 minimum pressure
Table 2. Watch and warning summary for Tropical Storm Miriam, 15-17 September 2000. Date/Time
(UTC)Action Location 15 / 2100 Tropical Storm Warning issued Baja California peninsula south of 24°N latitude 17 / 1500 Tropical Storm Warning discontinued Baja California peninsula south of 24°N latitude
Figure 1. Best track positions for Tropical Storm Miriam, 15-17 September 2000.
Figure 2. Best track maximum sustained surface wind speed curve for Tropical Storm Miriam, 15-17 September 2000, and the observations on which the best track curve is based.
Figure 3. Best track minimum central pressure curve for Tropical Storm Miriam, 15-17 September 2000, and the observations on which the best track curve is based.
