Norman made landfall as a tropical storm over southwestern Mexico producing
a. Synoptic history
The southern extension of the tropical wave which triggered Hurricane Gordon
in the Gulf of Mexico continued moving westward over central America and
Mexico from 14 to 16 September. The interaction of the tropical wave with a
large cyclonic low-level gyre which had persisted over the eastern Pacific
for a few days produced a large area of disturbed weather. Initially, the
shower activity was widely-scattered and did not become concentrated until
18 September when the disturbance was located about 180 n mi south-southwest
of Acapulco, Mexico. The cloud pattern gradually became organized and
developed a circular mass of deep convection with a well-defined outflow. It
is estimated that a tropical depression formed at 0000 UTC 20 September
about 180 n mi south-southeast of Manzanillo.
The depression drifted northward while embedded within a weak steering flow.
It slowly improved in organization and became a tropical storm by 1200 UTC
20 September. Ships in the area suggested strengthening and Norman reached
its peak intensity of 45 knots and minimum pressure of 998 mb at 1800 UTC.
A couple of hours later, Norman made landfall between Lazaro Cardenas and
Colima and began to weaken.
The depression center moved slowly northwestward over the high terrain of
southwestern Mexico while maintaining an area of very deep convection
primarily within bands over water. The poorly-defined center of the
depression moved back over water just to the north of Puerto Vallarta and
turned northward. The depression never recovered from its passage over the
mountains and Norman made its second landfall as a tropical depression in
the vicinity of Mazatlan near 1500 UTC 22 August. It then dissipated over
land shortly thereafter. The best track is listed in
Table 1 and is plotted
in Figure 1.
b. Meteorological statistics
Figure 2 and Figure 3
show the best track curves for maximum sustained 1-min surface
winds and minimum central pressure data, respectively, as functions of time.
These plots include Dvorak satellite classification estimates and surface
observations. Norman was upgraded to tropical storm status based on
two ship reports: The Imwanuma Maru reported 38-knot winds and a
pressure of 1001.5 mb at 1200 UTC on the 20th and the
Star Grip reported 39 knots and 1003 mb pressure at 1300 UTC on the
same day. Both ships were just to the west of the center. Large amounts of
rain occurred over southwestern Mexico. Official reports from the Servicio
Meteorologico Nacional de Mexico show a maximum of 14.0 inches in
Callejones, Colima and 9.5 inches in La Villita, Michoacan.
c. Casualties and damages
Despite the heavy rains, no reports of deaths or damage were received at the
National Hurricane Center associated with Norman.
d. Forecast and warning critique
Norman was a short-lived tropical storm, so there are no meaningful forecast
verification statistics. However, since the early stages of the development
of Norman, it was emphasized in the public tropical cyclone advisories that
torrential rains were expected over portions of southwestern Mexico. In
addition, once the system consolidated and became a tropical depression, a
tropical storm warning was issued for a portion of the coast of Mexico from
Zihuatanejo to Manzanillo at 0300 UTC 20 September and was discontinued 24
hour later after the system moved inland. Norman was forecast to remain as
a tropical depression after it moved back over water. Therefore, a tropical
storm warning was not necessary for the area of Mazatlan, but the potential
for heavy rains continued to be emphasized.
Best track for Tropical Storm Norman , 20-22 September, 2000.
|Lat. (°N)||Lon. (°W)
|20/0000||16.8||103.4||1008|| 25||tropical depression|
|20/2000||18.4||103.2||1000||45||landfall west of Lazaro Cardenas|
|22/1500||23.1||106.3||1006||25||landfall near Mazatlan|
Best track positions for Tropical Storm Norman, 20-22 September 2000.
Best track maximum sustained wind speed curve for Tropical Storm
Norman, 20-22 September 2000.
Best track minimum central pressure curve for Tropical Storm Norman, 15-17