Tropical Cyclone Report
Tropical Storm Lorena
2 - 4 October 2001
Stacy R. Stewart
National Hurricane Center
30 November 2001
Lorena was a short-lived tropical storm that briefly threatened
a. Synoptic History
The tropical wave that eventually developed into Lorena moved
off the west coast of Africa on 13 September. The poorly-defined
wave tracked rapidly westward across the Atlantic for more than a
week. There was little or no thunderstorm activity associated with
the wave until it moved across Central America on 27 September.
Significant deep convection finally developed on 29 September and
satellite classifications began on 30 September when the system was
located about 300 miles south of Acapulco, Mexico. The wave
possessed a well-defined closed low-level circulation at that
Convection steadily increased and banding features developed
during the day on 1 October. Satellite intensity estimates indicate
the system became Tropical Depression Thirteen-E at 0000 UTC 2
October. By 1200 UTC, QuikSCAT satellite-derived winds (data not
shown) revealed that the low-level circulation had tightened up
considerably and satellite intensity estimates indicated the
depression had strengthened into Tropical Storm Lorena about 350 n
mi south-southwest of Acapulco. Lorena tracked steadily
west-northwestward at 8 to 12 knots the remainder of the day and
gradually turned toward the northwest early on 3 October. The peak
intensity of 50 kt occurred around 1200 UTC later that day as
Lorena took a more northerly track when it was located about 180 n
mi southwest of Manzanillo, Mexico.
By 0000 UTC 4 October, Lorena's forward speed had decreased to
around 6 to 8 knots and strong upper-level southwesterly shear
began to adversely affect the cyclone. Lorena weakened to a
tropical depression at 1200 UTC and dissipated into a
non-convective low later that day about 120 n mi southwest of
Puerto Vallarta, Mexico. The remnant low-level cloud circulation
remained offshore and persisted for another day or so before
completely dissipating just west of Cabo Corrientes, Mexico.
The "best track" chart of Tropical Storm Lorena's path is given
in Figure 1, while the best track positions and intensities are
listed in Table 1.
Wind and pressure plots are shown in Figure 2 and
Figure 3, respectively.
b. Meteorological Statistics
Observations in Lorena (Figure 2 and Figure 3)
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 53rd Weather
Reconnaissance Squadron of the U. S. Air Force Reserve Command.
Lorena's peak intensity of 50 kt at 1200 UTC 3 September is
based on compromise of Dvorak satellite classifications from TAFB,
SAB, and AFWA. Since Lorena was forecast to make landfall along the
southwestern coast of Mexico near hurricane strength, an Air Force
Reserve reconnaissance aircraft was dispatched to investigate the
system on 3 October. Flights into the cyclone occurred between 1700
and 2300 UTC 3 October, after Lorena had attained its peak
intensity. The aircrew found that Lorena had already begun to
rapidly weaken, based on 700 mb flight-level winds of only 29 kt.
However, two dropwindsondes released about 100 n mi northeast of
the center (outside of any convection) indicated wind speeds of 25
to 30 kt in a deep layer from the surface to 750 mb. This wind data
would suggest that minimal tropical storm force winds possibly
existed closer in near the cyclone center.
Ship reports of winds of tropical storm force associated with
Lorena are given in Table 2. There were no reports of tropical
storm force winds over land since Lorena rapidly dissipated before
the outer wind field could reach the coastal areas of southwestern
c. Casualty and Damage Statistics
No reports of damage or casualties associated with Tropical
Storm Lorena were received by the National Hurricane Center.
d. Forecast and Warning Critique
Owing to the short-lived nature of Tropical Storm Lorena, no
meaningful forecast verification statistics are available since
only two forecast cycles were available at 48 hours and none at 72
hours. However, the errors associated with the limited number of
forecasts were near the statistical average for the past 10
Table 3 lists the watches and warnings issued
for Tropical Storm
Lorena. However, since Lorena weakened faster than
expected, none of the tropical storm warnings or hurricane watches
Table 1: Best track for Tropical Storm Lorena, 2 - 4 October 2001.
|Lat. (°N)||Lon. (°W)
|02 / 0000||11.9||102.0||1006||30||tropical depression
|02 / 0600||12.0||103.1||1005||30||"
|02 / 1200||12.6||104.3||1004||35||tropical storm
|02 / 1800||13.2||105.4||1002||40||"
|03 / 0000||14.3||106.0||1002||40||"
|03 / 0600||15.0||106.3||1000||45||"
|03 / 1200||15.7||106.5||997||50||"
|03 / 1800||16.2||106.7||1000||45||"
|04 / 0000||16.8||106.7||1004||40||"
|04 / 0600||17.6||107.0||1004||35||"
|04 / 1200||18.5||107.0||1006||30||tropical depression
|04 / 1800||19.6||106.7||1009||25||"
|05 / 0000||dissipated
|03 / 1200||15.7||106.5||997||50||minimum pressure
Table 2: Selected ship reports with
winds of at least 34 kt for Tropical Storm Lorena,
2-4 October 2001. Asterisk (*) indicates pressure
was not corrected to sea-level.
|Ship Name or Call Sign||Date/Time (UTC)||Lat. (°N)||Lon. (°W)||Wind dir/speed (deg/kt)||Pressure (mb)
|ELXX7||03 / 1730||18.7||104.3||090/35 ||1011.0*
|SHIP||03 / 1800||18.2||104.6||100/35 ||1012.7
|ELXX7||03 / 2115||17.9||103.2|| ||1007.0*
Table 3: Watch and warning summary, Tropical Storm Lorena, 2 - 4 October 2001.
|03 / 0300||Tropical Storm Warning Issued||Punta San Telmo northward to Mazatlan, Mexico
|03 / 0300||Hurricane Watch Issued||Punta San Telmo northward to Mazatlan, Mexico
|04 / 0300||Hurricane Watch Discontinued||Punta San Telmo northward to Mazatlan, Mexico
|04 / 1500||Tropical Storm Warning Discontinued||Punta San Telmo northward to Mazatlan,
Best track positions for Tropical Storm Lorena, 2-4 October 2001.
maximum sustained surface wind speed curve for Tropical Storm
Lorena, 2-4 October 2001, and the observations on which the best
track curve is based. Aircraft observations have been adjusted for
elevation using 90%, 80%, and 80% reduction factors for
observations from 700 mb, 850 mb, and 1500 ft,
minimum central pressure curve for Tropical Storm Lorena, 2-4
October 2001, and the observations on which the best track curve is