In this season a total of 17 tropical organisms originated, two of those remained in the category of tropical depression, six developed into tropical storm and nine reached the hurricane intensity. 65% of those organisms had their origin in tropical waves. On Chart 1 the classification of tropical hurricanes for the Atlantic is presented, according to the intensity of the maximum sustained winds on surface. Four out of the nine hurricanes were intense (Category 3 or superior in the Saffir-Simpson scale, see Chart 2). Erin and Felix were hurricanes of category 3, while Iris and Michelle ended up reaching category 4. These last two stood out, not only for the intensity, but also for having been the only hurricanes that affected terrestrial areas with all their force, causing loss of lives and in the economy to countries of Central America and Cuba.
| Chart 1. Classification of tropical storms according to the intensity of the maximum sustained winds on surface. |
|
Classification |
Maximum sustained wind in km/h (mean in one minute) |
|
Tropical depression |
<63 |
|
Tropical storm |
63 - 117 |
|
Hurricane |
>117 |
| Chart 2. Classification of hurricanes according to the Saffir-Simpson scale. |
|
Category |
Central pressure (hPa) |
Sustained maximum wind (km/h) |
Damages |
|
1 |
³ 980 |
118 - 153 |
Minimal |
|
2 |
979 - 965 |
154 - 177 |
Moderate |
|
3 |
964 - 945 |
178 - 209 |
Extensive |
|
4 |
944 - 920 |
210 - 250 |
Extreme |
|
5 |
< 920 |
>250 |
Catastrophic |
When observing the monthly distribution of tropical storms on Chart 3, the month of October highlights, as it amply surpasses the mean value for the period 1886-2000 and equals the seasons of 1923 and 1969, it is only overcome by those of 1887 and 1950 with six storms developed. It was also of interest in October the formation of the two most intense hurricanes of the season. In November a great hurricane intensified in the Caribbean, native of this area, something that had only happened in 1912 and in 1999, besides three hurricanes intensifying in the month, a fact that shows for the first time since 1886.
The most active period was between September 7 and October 7, with the formation of tropical depression number 9 and the presence of six tropical storms, five of which became hurricanes. In this season the period of more activity started with some delay and didn't go up until September 8 when a storm reached the hurricane category. That delay was due fundamentally to how intense the subtropical anticyclone of the Atlantic remained and to the upper tropical tropospheric troff.
| Chart 3. Monthly mean frequency of tropical hurricanes for the period 1886-1999 and behavior in the year 2001. |
|
Period |
June |
July |
August |
September |
October |
November |
|
1886 - 2000 |
0.5 |
0.7 |
2.1 |
2.9 |
1.8 |
0.4 |
|
2001 |
1 |
0 |
3 |
4 |
5 |
2 |
On Chart 4 a summary of the characteristics of the tropical hurricanes is presented and their trajectories are shown in Fig.1. In this figure it is appreciated that ten tropical hurricanes developed on the Atlantic Ocean (Chantal, Dean, Erin, Félix, Humberto, Jerry, Karen, Lorenzo, Noel and Olga), three over the Gulf of Mexico (Allison, Barry and Gabrielle) and two over the Caribbean Sea (Iris and Michelle). Only two hurricanes reached this category below 24 degrees of latitude North, and they both developed on the Caribbean.
In the season of 2001 several countries were affected directly by some organism. The United States suffered the effects of Allison, Barry and Gabrielle. Belize was impacted by Chantal and Iris. The Lesser Antilles were affected by Chantal, Iris and Jerry, in their weaker stages and lastly Nicaragua, Cuba and The Bahamas, that were lashed by Michelle in different stages of its evolution.
| Chart 4. Tropical storms and hurricanes of the cyclone season of 2001 in the North Atlantic. |
|
Name |
Date of beginning |
Date of dissipation |
Maximum wind (km/h) |
Minimum pressure (hPa) |
Date and hour (UTC *) in that the maximum intensity is reached |
Saffir -Simpson scale |
|
Allison |
6/5 |
6/7 |
95 |
1002 |
6/5 1852 |
- |
|
Barry |
8/2 |
8/6 |
110 |
990 |
8/5 1154 |
- |
|
Chantal |
8/15 |
8/22 |
110 |
997 |
8/19 0604 |
- |
|
Dean |
8/22 |
8/28 |
110 |
992 |
8/27 1800 |
- |
|
Erin |
9/1 |
9/14 |
195 |
968 |
9/9 1952 |
3 |
|
Félix |
9/7 |
9/18 |
185 |
965 |
9/13 1800 |
3 |
|
Gabrielle |
9/11 |
9/18 |
130 |
980 |
9/14 1009 |
1 |
|
Humberto |
9/21 |
9/27 |
165 |
970 |
9/26 1200 |
2 |
|
Iris |
10/4 |
10/9 |
230 |
948 |
10/9 0000 |
4 |
|
Jerry |
10/6 |
10/8 |
85 |
1003 |
10/7 0600 |
- |
|
Karen |
10/12 |
10/15 |
130 |
982 |
10/14 0900 |
1 |
|
Lorenzo |
10/27 |
10/31 |
65 |
1007 |
10/30 0000 |
- |
|
Michelle |
10/29 |
11/6 |
220 |
933 |
11/3 1921 |
4 |
|
Noel |
11/5 |
11/6 |
120 |
986 |
11/5 1600 |
1 |
|
Olga |
11/24 |
12/4 |
150 |
973 |
11/27 1800 |
1 |
*UTC: Means Universal Coordinated Time and it differs in +5 hours from the local time for Cuba (Meridian 75 (W).
Figure 1. Trajectories of tropical hurricanes on the season of 2001. The positions are given every 6 hours and the signals with the day they correspond 12:00 UTC. (. . .) means the phase of tropical wave and (*..... *) that of depression.
