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CABO SAN LUCAS

TROPICAL CYCLONES AFFECTING CABO SAN LUCAS

Specific tropical cyclone data, containing storm tracks, wind and pressure data, etc., are available starting in 1949. However, prior to 1966 satellites were not used operationally and there are likely some storms that tracked well offshore from Cabo San Lucas and are missing from the data set. Records of storms off the west coast of Mexico (the Eastern North Pacific Basin) are shorter than they are for other basins and, before 1949, the records are so fragmented that they are of little use in climatological analysis. The reason for this is that most of the storms in the Eastern Pacific do not affect land and zonal shipping routes. After the beginning of the operational satellite era in 1966, many more storms than previously thought were noted between Mexico and the Hawaiian Islands.

Table V-1 contains a descriptive history of all the recorded 118 tropical cyclones and hurricanes passing within 180 nmi of Cabo San Lucas during the 53-year period 1949-2001. Unless otherwise indicated, all of the tropical cyclone statistics utilized in this report for storms passing within 180 nmi of Cabo San Lucas are based on the data set used to compile Table V-1.

The majority of tropical cyclones originate in the area to the south-southeast of Cabo San Lucas and 55 % of the tropical cyclones originated within 72 hours of the Port (Figure V-15). Accordingly, ships transiting from the Port need to be aware of the rapid development of tropical cyclones as they proceed through what the pilots refer to as "hurricane alley."

Cabo San Lucas has a higher probability of observing damaging tropical cyclone winds than in the Ports of La Paz or Pichilingue. The Port of Cabo San Lucas is not protected from high seas, winds, swell, or storm surge from approaching tropical cyclones and the Port has experienced extensive damage during recent years. The average speed of advance for tropical cyclones at the latitude of Cabo San Lucas is about 11 kt.

Although the tropical cyclone season for Mexico is considered to extend from June through October, Table V-2 shows that Cabo San Lucas season extends from June through November. However, only two storms were recorded during November throughout the 53-year period 1949-2001. September had the greatest tropical cyclone activity, with 45 of 118 storms (38.1%) occurring during that month. Of the 118 storms in the data set, 48 were of hurricane strength (greater than or equal to 64 kt) within 180 nmi of Cabo San Lucas. Table V-2 also shows the average direction towards which storms were moving when they were at CPA to Cabo San Lucas. The average movement for all storms is 338° at 11 kt. The average speed by month is very consistent and ranges from 10-13 kt.

Figure V-16 shows in seven-day increments the annual distribution of the 118 tropical cyclones that entered the 180 nmi threat radius around Cabo San Lucas. The period of maximum activity, from June 11th through November 30th, is clearly shown. It is also interesting to note the increased activity during September and the first week of October.

Figure V-17 depicts the chronology of the 118 tropical cyclones that passed within 180 nmi of Cabo San Lucas during the 53-year period 1949-2001. As shown in the figure, there is an average occurrence rate of 2.23 storms per year for all tropical cyclones, regardless of intensity. The recurrence interval of all tropical cyclones is 0.4 years. There have only been six years since 1949 when no tropical cyclone entered Cabo San Lucas's 180 nmi threat radius. 1956, 1961, 1980, 1991, 1992 and 1997 had no storms passing within 180 nmi of Cabo San Lucas.

Figure V-18 shows the octants from which the 118 tropical cyclones were moving when they were at CPA to Cabo San Lucas. As shown in the figure, the predominant threat directions are from the southeast and south octants. A total of 49 storms (41.5%) approached from the southeast and a total of 32 (27.1%) approached from the south. It must be remembered that the figure represents tropical cyclone movement at CPA, and may not represent the tropical cyclone's initial movement towards Cabo San Lucas. Note that both the threat direction and the slow speed of movement are important considerations for evasion at sea or making storm preparations in port.

Figure V-19, Figure V-20 and Figure V-21 show the tracks of the 118 tropical cyclones separated into three periods. As shown in all three figures, the movement of the 118 tropical cyclones that entered Cabo San Lucas' 180 nmi radius can be described as fairly consistent. It is important to note that 55 % of all storms developed within 72 hours from the closest point of approach to Cabo San Lucas. During the June 1-August 31 period, 1949-2001, the tropical cyclone tracks branch out north of Cabo San Lucas with the majority of the tropical cyclones passing west of the Port. During the September 1- 30 period, the majority of storms track parallel to the west coast of Mexico and branch out after passing north of Cabo San Lucas. During the October 1-November 30 period, the majority of storms recurve to the east and most pass east of the Port.

Figure V-22, Figure V-23, and Figure V-24 are the statistical summaries of threat probability based on tropical cyclone tracks for the period 1949-2001. The summaries are separated into three periods to coincide with the tracks presented in Figure V-19, Figure V-20 and Figure V-21. The data is presented with solid thin lines representing "percent threat" for the 180 nmi radius circle surrounding Cabo San Lucas. The solid thick lines represent approximate approach times to Cabo San Lucas based on the climatological speeds of movement. In Figure V-22 for example, a tropical cyclone located near 18°N 105°W has approximately a 40 % probability of passing within 180 nmi of Cabo San Lucas during the June 1 to August 31 period. In addition, this tropical cyclone would reach Cabo San Lucas in 1 1/2 days if the speed remains close to the climatological normal for tropical cyclones passing within 180 nmi of Cabo San Lucas.

Wind

The Port area of Cabo San Lucas is an open bay that is vulnerable to wind, particularly from tropical cyclones. Hurricane Julliette in September 2001, with a CPA of 57 nmi to the west-southwest, impacted the Port with 43 kt sustained winds and gusts up to 65 kt.

A notable weather phenomenon that occurs periodically during the summer hurricane season is a "Torito." These strong southerly squalls can exist and reach 45-50 kt-sustained winds for ½ to 1 hour in duration. Toritos occur during the months of July and August. According to the Captain of the Port during the Site Visit in February 2002, there were two Toritos that impacted the Port in 2001. Indicators of this event are thunderstorms showing on the horizon from the southeast through southwest.

Wind and pressure measuring instruments are located in the Captain of the Port (COTP) office and the Mexican Navy Detachment Office located west of the Inner Harbor and close to the south entrance to the Inner Harbor, respectively. The measured winds are considered to be representative of those experienced by ships in the Port of Cabo San Lucas. However, winds are probably stronger over the water in the Outer Harbor than indicated by instrumentation at these locations. Wind, temperature, and pressure is also measured at Cerro Las Tetas Meteorological Station (22°52.6'N 109°57.6'W) with University of La Paz instrumentation and at the CNA Meteorological Station on the highest hill located at 22°53.3'N 109°55.5'W run by Comision Nacional del Aqua (Mexico National Weather Commission).

Prevailing winds along the west coast of Baja California are northwest and may blow steadily from that direction for about eight months of the year. Locally within Bahia San Lucas, the winds during these same months are from the west. The Captain of the Port stated during the site visit in February 2002 that there is no funneling of the wind locally as it approaches the Bay over the hills from the west.

Winds from the southeast through south have the greatest impact on the Port and tropical cyclones passing to the west are the most dangerous. During November through February, winds from southeast to southwest are frequent with occasional moderate southeast gales. During December and January, heavy winds from a direction between north and northeast are likely to occur and usually last 1-3 days. Winds normally increase during the winter after 1100 in the morning and decrease again after 1900. Fog may occur in all seasons, but mostly during the summer months, setting in at night or in the early morning and clearing by 1000.

Waves

Ships tied up at the pier in Cabo San Lucas are normally protected from open ocean waves with the exception of those from tropical cyclones. The anchorage areas are particularly affected by open ocean waves and swell. Although no specific information on maximum wave heights was obtained during the site visit in February 2002, small boat operations are discontinued when swell reaches 2-3 ft (.6-.9 m) and ships are not safe at anchorages with sustained winds greater than 25 kt.

Storm Surge

Hurricane Juliette produced high seas and storm surge that had a significant impact on the beaches adjacent to the Outer Harbor and on the piers and facilities in the Inner Harbor. The Captain of the Port estimated during the site visit in February 2002 that storm surge could be as high as 19.7 ft (6 m) with storms approaching Cabo San Lucas from the south or southeast.

Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/mexico/cabosanl/text/sect7.htm