Very dangerous Hurricane Lane heads for landfall

Hurricane Lane has intensified into a small but very dangerous Category 3 hurricane, and is now bearing down on the Pacific Mexican coast north of the resort town of Mazatlan. The historical map of Eastern Pacific hurricanes shows that Lane is the strongest September hurricane ever to affect this region of the Pacific coast of Mainland Mexico. Lane passed about 45 miles to the west of Matazlan this morning at 5am PDT. Hurricane force winds extend out only 30 miles from the center of Lane, and Mazatlan airport has recorded top winds of only 25 mph so far today. Lane is responsible for one death. Lanes' heavy rains triggered a landslide yesterday that killed a 7-year-old boy in Acapulco. Lane brushed the Mexican coast between Acapulco and Puerto Vallarta Friday, bringing heavy rains of 4-8 inches, then made a direct hit on a group of islands called the Islas Tres Marias as a Category 2 hurricane. There is no word yet on how the islands fared. The islands are home to a large penal colony.


Figure 1. Latest satellite image of Lane, updated every half hour.

Cabo San Lucas radar shows that Lane has developed concentric eyewalls, and is probably near peak intensity. The main threat from Lane is his winds. Lane has a small eye about ten miles in diameter, and a small region of the Mexican coast about 20 miles wide will be subject to the extreme winds of the eyewall. These 125 mph winds will cause tremendous damage. Hopefully, Lane will miss the populated towns of El Dorado and La Cruz and come ashore on a relatively sparsely populated section of coast. The other major threat is rainfall. Ten inches of rain will be common in the mountainous region of Mexico Lane is expected to cross, triggering flash floods. Storm surge flooding should be less of a problem, since the ocean waters are deep offshore, which will allow only a six-foot storm surge to build.

Lane is the sixth major hurricane in the Eastern Pacific this year. It is often the case that a quiet year in the Atlantic is offset by an active year in the Eastern Pacific, and vice versa. That has certainly been the case the past two years. The Atlantic has seen only one major hurricane this year. Last year the Atlantic had seven major hurricanes, and the Eastern Pacific just one. The difference in activity between the two ocean basins is not fully understood, but has been commonly linked to the El Nino phenomena.

The mountains of central Mexico should dissipate Lane within three days, and moisture from the storm is no longer expected to reach the U.S.

Helene becomes a hurricane
Helene has intensified into a hurricane this morning, and now has a eye, well-formed low-level spiral bands, and some solid and improving upper-level outflow. Helene is over warm 27-28C waters, shear is a low 5-10 knots, and the storm should intensify into a Category 2 hurricane by Monday.

Helene may be a threat to Bermuda and/or the Maritime provinces of Canada, but the odds of a strike on the U.S. are less than 10%. History shows that the large majority of hurricanes that traverse this part of the Atlantic end up recurving. One very notable exception is the famed New England Hurricane of 1938, which followed a very similar path to Helene's current track. Two strong troughs of low pressure are expected to push off the East Coast over the next week. If the first trough does not pull Helene northwards far enough to recurve her out to sea, the second one should almost certainly finish the job--before Helene can make it all the way to the U.S. It is too early to tell what the risk might be to Bermuda; the exact strength of the first trough 4-5 days from now is uncertain, and will determine how far west Helene is able to penetrate. The latest run of the GFS model puts Helene very near Bermuda on Sunday September 24.

Gordon on the decline
Hurricane Gordon is barely a hurricane, thanks to some strong shear and dry air. Margie Kieper did a nice job in her View from the Surface blog documenting Gordon's demise. Gordon is headed northward out to sea, and is not a threat to land.

The rest of the tropical Atlantic
A strong tropical wave with plenty of spin but only a little thunderstorm activity is just off the coast of Africa near the Cape Verde Islands, and is headed northwest out to sea. This system may show some slow development over the next few days.

Remainder of hurricane season outlook
I posted my outlook for the remainder of hurricane season yesterday, in case you missed it.

I'll have an update Sunday morning.
Jeff Masters