Weather/Tactics Discussion (Part 7)
PART 7: TROPICALS
Hurricane Season in the EPAC, east of 140 W, begins May 15. Tropical development in the EPAC is monitored by the National Hurricane Center (NHC) in Miami, FLA.
West of 140W, to 180W, the Central Pacific (CPAC) Hurricane Season begins June 1, runs to Nov. 30, and is monitored by the Central Pacific Hurricane Center (CPHC) in Honolulu.
Both Hurricane forecast centers are under the aegis of NOAA's National Weather Service.
On average, 15 named storms form each season in the EPAC. 87% of these named storms form below latitude 20 N. I estimate less than 25% of named EPAC Tropical Storms (TS) in June cross west of longitude 140W before they are downgraded, or dissipate. Even fewer TS develop west of 140.
The formation of a Tropical Storm begins and ends with a TROPICAL WAVE. Development then may proceed to a TROPICAL DISTURBANCE, A TROPICAL DEPRESSION, A TROPICAL STORM, and finally a HURRICANE.
In 50 years of Hawaiian racing, only one Tropical Storm has crossed tracks with a Transpac Race, that being TS BERNICE in the 1965 LA-Hono Transpac on July 11-12. BERNICE, tracking NW, blew 40-50 knots with 15-20 foot following seas from the ESE for 12 hours, and propelled TICONDEROGA to break the elapsed time record in her classic race against STORMVOGEL. Both 72 footers suffered damage.
During the 1978 SHTP, Hurricane CARLOTTA passed just south of the Big Island of Hawaii, then dissipated. The fringes of CARLOTTA's remnants, a tropical depression (TD,) brought clouds and rain over the leading SHTP finishers, making an approach to Kauai using celestial navigation problematical.
Tropical Storm development requires ocean water temps warmer than 80 degrees to support formation. A TS crossing into water cooler than 80 F (27C) degrees will promote dissipation.
The current (mid-May, 2010) water temp offshore of Kauai is 74 degrees. This temperature isotherm extends all the way to near Cabo San Lucas, Mexico. The water temp near Kauai may rise to near 75 degrees by mid-July
The SHTP fleet will be sailing SW towards Hawaiian waters. This course from the NE means the SHTP fleet will be sailing in cooler waters than would support TS development. Not to say it won't happen someday: Hurricane DANIEL http://www.solar.ifa.hawaii.edu/Trop...ve/nep2000.gif threatened the anchored Pacific Cup fleet in Kaneohe after the 2000 Pacific Cup.
DANIEL would have been the largest "TROPICAL" to reach the Hawaii Islands since Hurricane INIKI devasted Kauai on Sept. 11, 1992. DANIEL resulted in storm warnings being hoisted for the Big Island, Maui, Lanai, and Molokai, and a tropical storm watch for Oahu and Kauai.
Honolulu West Marine sold out of anchors and chain. 24 hours before landfall, DANIEL was downgraded to a Tropical Storm, and curved onto a path north of the Islands, bringing muggy conditions and high surf to Kauai. But no wind.
Besides Hurricane INIKI, only two other hurricanes in recorded weather history have struck Kauai: Hurricane DOT on August 6, 1950, and Hurricane IWA on Nov.23, 1982. The chances of a hurricane or TS hitting Kauai or affecting the SHTP fleet are slim. About 1%. If one were to threaten, there is no safe harbor, including Port Allen and Nawiliwili, on Kauai. The best option might be putting to sea and using Kauai as a shield, staying on the opposite side of the island from the hurricane's track.
Although the chances of a hurricane or TS are remote, their influences can be felt by Transpac racers far to the North. Most EPAC hurricanes form off southern and central Mexico, and travel W or NW, usually tracking between 10-20 degrees North Latitude before falling apart east of 140W. Cross swells from the South generated by a TS can reach the SHTP fleet. The beam-to swell can make downwind steering difficult.
More importantly, a dissipating TS will result in a "TROPICAL WAVE" or "S" bend in the isobars as it passes to the south. A TROPICAL WAVE is a trough of low pressure represented on a Weather Fax map by a vertical dashed or solid line traveling E to W. In summer, TROPICAL WAVES transit the EPAC and CPAC several times/month.
Most TROPICAL WAVES pass to the south of the Hawaiian Island Chain. Some, however, pass over Hawaii or even to the north.
In 1998, while at anchor in Hanalei Bay, the remnants of Hurricane Darby passed 200 miles north on 8/1, bringing torrential rain and light shifting winds to departing Single Handers heading back for the Mainland. The Hanalei anchorage became disorganized, with wildly swinging boats. 10 days later, 8/11-8/12, the remnants of Hurricane Estelle passed 60 miles north of Hanalei, causing the Tradewinds to reverse and blow from the West for 36 hours.
With the approach of a TROPICAL WAVE, the wind will initially back into the N. After the passage of the WAVE, the wind will veer into the SE, S, or even SW. And go light. Close reaching into a Transpac finish on port tack is not as unusual as might be thought. Maybe 1 in 10 Transpacific races are at some point affected by the backside of a TROPICAL WAVE.
After INIKI's damage, the National Hurricane Center really woke up. Predictions now are timely, and accurate out to 5 days or more. Hawaiian Weather and Civil Defense are also keenly alert, and warnings can be expected well in advance of any Tropical approach.
Tropical Development should not be a big worry for SHTP racers. However, attention should be paid to the possibilities. .
