Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 9:02 PM GMT on August 30, 2006
Tropical Depression Ernesto steamed north across Florida today, crossing over Lake Okeechobee, headed for an exit from the Florida coast north of Cape Canaveral. The storm has maintained its integrity, as seen in satellite animations and radar imagery. Although Ernesto's winds have dropped below tropical storm force, its central pressure has stayed about 1002 mb, only a 1 mb rise from when it made landfall. The considerable blow-up of heavy thunderstorm this afternoon over Ernesto's center is due to the normal daytime increase in thunderstorm activity due to solar heating of the Florida landmass. Rainfall amounts over Florida have generally been below 4 inches, and Ernesto has not been much of a problem for the state.
Once Ernesto re-emerges into the Atlantic early Thursday morning, it will re-intensify over water. None of the forecast models or the official NHC forecast are calling for this to become a hurricane, though. The passage over Florida has weakened it to the point where it would take more time over water than Ernesto will have. It is possible that Ernesto will intensify very little, as happened when it popped off the coast of Cuba. The most likely intensity at its second landfall in South Carolina is 40-55 mph.
Hurricane John strengthened into a very dangerous Category 4 hurricane this afternoon, and is already bringing tropical storm force winds to the Mexican coast. John is expected to move parallel to the coast over the next two days, but close enough to bring hurricane force winds to the coast at times. Any slight deviation towards the coast will bring the hurricane's dangerous core ashore, and would make John one of the strongest hurricanes ever to hit the Pacific coast of Mexico. The area of the coast that pokes out farthest into the ocean, just south of Manzanillo, is at highest risk of a strike, and the latest 12Z (8am EDT) runs of both the GFDL and NOGAPS models are calling for a strike here. Wind shear is light and forecast to remain low, and sea surface temperatures (Figure 1) are a very warm 30 C under the hurricane--about 1-2 degrees C above normal for this time of year.
Figure 1. Current sea surface temperatures along the Pacific coast. Temperatures in the Gulf of California may not be accurate, due to difficulties retrieving the temperature via satellite measurements in such a narrow body of water. The red line separating blue colors from yellow marks the 26 C isotherm--the critical temperature needed to sustain a tropical cyclone. Note the very cool waters extending from the California border southwards along the coast. This long stretch of cool water will make it difficult for John to hold together if it tries to approach California. Image credit: NOAA/AOML.
Is John a threat to the U.S.?
Eastern Pacific hurricanes are most likely to impact the U.S. in El Nino years, where the ocean along the Mexican coast heats up to much above normal temperatures and can fuel very intense hurricanes. This was the case in 1997, when Category 5 Hurricane Linda, the most intense hurricane ever observed in the Eastern Pacific, moved parallel to the coast and threatened California. The National Hurricane Center issued several advisories for Linda alerting San Diego to the possibility of receiving tropical storm force winds from Linda. The storm turned out to sea before reaching California, however.
This is not an El Nino year, but recent warming of the waters in the Eastern Pacific has led some El Nino experts wondering if a late-arriving El Nino might be on the way. Water temperatures along the Pacific coast of Mexico are 1-2 degrees C above normal all the way to the California coast, giving 2006 the possibility of allowing a tropical storm to reach California. It is very rare for an Eastern Pacific storm to move far enough north to affect the Arizona or California. Since 1900, only four tropical cyclones have brought tropical storm force winds to the Southwestern United States: an unnamed tropical storm that made landfall near Long Beach, CA, in 1939 (52 mph winds south of L.A.); the remnants of Hurricane Joanne in 1972; the remnants of Hurricane Kathleen in 1976 (76 mph wind gust at Yuma, AZ); and the remnants of Hurricane Nora in 1997. In addition, a hurricane just missed making landfall in October 1858 and brought hurricane force winds to San Diego and tropical storm force winds all the way to Los Angeles.
In order to affect California, a tropical cyclone would have to be moving quickly, so the the cold waters off the coast would not weaken it too fast. The alternative would be for the storm to barrel up the narrow Gulf of California, where water temperatures remain warm all the way to the end. To my knowledge, no such storm has ever been able to shoot more than half way up the narrow Gulf of California before dashing itself to pieces on the rugged terrain on either side. I'd be surprised if John manages to bring tropical storm force winds to the U.S.
Super Typhoon Ioke
The incredible Category 4 Supertyphoon Ioke continues to rumble towards tiny Wake Island in the Pacific. The entire population of the island has been evacuated to Hawaii. NOAA's National Ocean Service has a station on Wake Island, and the current conditions at 3pm EDT were sustained winds of 34 mph gusting to 44 mph, and the pressure at 999 mb and falling rapidly. It is expected that Ioke's storm surge may completely submerge the island. Ioke has a significant wave height of 50 feet, meaning that 1/3 of the waves in the storm are higher than that. Wow!
African tropical waves
A tropical wave near 12N 36W, a few hundred miles southwest of the Cape Verde Islands, has changed little in organization today. Some slow development of this system is possible over the next few days.
The large spiral of low clouds near 18N 46W surrounded by a large cloud of dry air and African dust continues to spin, but the thunderstorm activity near the center remains near zero this afternoon. The wave has some potential for development if it can find a moister environment. This is not likely until Sunday at the earliest, when it may be near Puerto Rico or the Bahamas.
I'll be back Friday morning with a new update.
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