Tropical Cyclone Report
Tropical Storm Lorenzo
27 - 31 October 2001
Miles B. Lawrence
National Hurricane Center
6 December 2001
Lorenzo was a short-lived tropical storm with winds to 35 knots
over the central north Atlantic Ocean.
a. Synoptic History
Lorenzo originated from a tropical upper tropospheric trough
that had persisted over the eastern North Atlantic Ocean. On 26
October, a low-level circulation developed beneath this trough. On
the next day, organized convection was sufficient to identify the
system as a tropical depression, centered about 750 n mi
south-southwest of the westernmost Azores. The "best track"of the
tropical cyclone begins at 1200 UTC on the 27th. A map
of the best track positions is shown in Figure 1 and six-hour center
positions, wind speeds, and central pressures are listed in
Time series curves of best track wind speed and pressure are
shown in Figure 2 and Figure 3.
The depression moved westward, steered by a deep-layer ridge
located to its north. It gradually turned northward on the
30th, as a strong trough in the westerlies and frontal
zone approached from the west. The low-level center was mostly
exposed to the west of the convection until this turn when some
deep convection flared up near the center. The depression is
estimated to have strengthened to Tropical Storm Lorenzo early on
the 30th. Lorenzo merged with the approaching frontal
zone on the 31st, while located about 600 n mi west of
the westernmost Azores.
b. Meteorological statistics
Satellite data is the primary basis for the best track values of
maximum 1-minute surface wind speed and minimum central surface
pressure. The satellite intensity estimates are plotted in
Figure 2 and Figure 3.
In addition, a QuikSCAT pass on the 30th showed
uncontaminated wind speeds to 35 knots. The ship 3ESP7 reported
winds from 37 to 43 knots on the 28th and
29th, as it moved near the depression. However, this
ship is estimated to have a positive wind speed bias of 23 knots,
based on a comparison with other ship reports by the Marine
c. Casualty and damage statistics
No deaths or damages are attributed to Lorenzo.
d. Forecast and warning critique
Lorenzo was a tropical storm for 30 hours and only four 12-hour
forecasts and two 24-hour forecasts were verified. The few official
track forecasts verified had track errors somewhat larger than the
previous ten-year average official errors. The few official
intensity errors were smaller than the previous ten-year
Table 1: Best track for Tropical Storm Lorenzo, 27 - 31 October 2001.
|Lat. (°N)||Lon. (°W)
|27 /1200||27.2||34.9||1010||30||tropical depression
|30 /0000||28.5||44.6||1007||35||tropical storm
|31 /1200||merged with frontal system
|30 /0000||28.5||44.6||1007||35||minimum pressure
Best track positions for Tropical Storm Lorenzo, 27-31
Best track maximum sustained surface wind speed curve
for Tropical Storm Lorenzo, 27-31 October 2001, and the
observations on which the best track curve is based.
Best track minimum central pressure curve for Tropical
Storm Lorenzo, 27-31 October 2001, and the observations on which
the best track curve is based.