99L a threat to Carolinas; Felix dies; Henriette does a double landfall

Hurricane Felix is no more. The high mountains of Honduras have dissipated the storm, just 24 hours after Felix smashed ashore near the Nicaragua/Honduras border with 160 mph winds and an 18-foot storm surge. Puerto Cabezas, a Nicaraguan Caribbean coast town of 40,000 people, took the worst of Felix's wrath. The town sits just 10 miles south of where the eye hit, and preliminary reports indicate much of the town was heavily damaged, and three people were killed. The big fear from Felix continues to be the heavy rains it is spawning over the mountainous regions of Nicaragua, Honduras, and El Salvador. So far, satellite estimates of rainfall show amount up to 125 mm (5 inches) have fallen, with up to another 5 inches expected by 8pm tonight (Figure 1). It is unlikely that rains of this magnitude can trigger the type of catastrophes suffered by the region during Hurricane Mitch and Hurricane Fifi. I am hopeful that Felix's major destruction will be confined to the small region near landfall in northeastern Nicaragua.


Figure 1. Forecast rain amounts for the 24 hours ending at 8pm EDT Wednesday September 5 (00 GMT September 6). Maximum rain amounts of about 125 mm ( 5 inches) are predicted over the region where Honduras, Nicaragua, and El Salvador meet, and also near the Belize/Guatemala border.

Carolinas at risk from tropical disturbance 99L
An area of disturbed weather (99L) that formed along an old frontal boundary appears to have developed into a subtropical depression, and may grow into a tropical storm over the next day or two. Strong upper level winds from the west are creating about 15 knots of wind shear over 99L, and satellite loops of 99L show the classic appearance of a weak, sheared system--a nearly exposed low level circulation system, with all the heavy thunderstorm activity pushed to one side by strong upper-level winds. This shear is forecast to remain between 15 and 25 knots over the next two days, which should allow some slow development. A QuikSCAT pass from 6:52am EDT showed that 99L has a vigorous closed circulation with top winds of 25-30 knots (30-35 mph), so in my book this system is already a subtropical depression. The reason I call it subtropical is because there is still clear evidence of a frontal boundary attached to 99L, evident as long band of clouds extending from the south side of the storm (Figure 2). The Hurricane Hunters are scheduled to investigate this system at 2pm EDT, and NHC may wait until then to see if 99L can maintain its strength before naming it a subtropical depression.

The computer models are all unanimous in developing 99L into a tropical storm. The preferred tracks are into North Carolina or South Carolina by Sunday or Monday. The HWRF, SHIPS, and GFDL intensity models are calling for a weak tropical storm, strong tropical storm, and Category 2 hurricane, respectively, when 99L makes landfall Monday in the Carolinas. Residents of the east coast of the U.S., and the Carolinas in particular, should carefully watch the development of 99L.


Figure 2. Visible satellite image of 99L showing the nearly exposed circulation center, and a front attached to the storm's south side. Image credit: NOAA.

African development?
The models unanimously forecast a tropical depression will develop near the Cape Verdes Islands off the coast of Africa 2-4 days from now. The models showed a similar degree of unanimity for the development of Hurricane Dean in a similar situation, so the chances of another named storm off the coast of Africa early next week are considerable.

Henriette hits Baja, heads for mainland Mexico
Hurricane Henriette hit the southern tip of Mexico's Baja as a Category 1 hurricane yesterday, and is on its way to a second landfall in mainland Mexico later today. This would make Henriette Mexico's second double landfalling hurricane this season--Hurricane Dean made a double landfall along the Atlantic side of Mexico, hitting the Yucatan Peninsula and mainland Mexico in the Bay of Campeche. Guasave radar and satellite loops show that Henriette is not very well-organized, but the hurricane should be able to maintain its strength over the warm waters of the Sea of Cortez and come ashore as a weak Category 1 hurricane or strong tropical storm. Henriette killed one person due to high surf in Cabo San Lucas yesterday, and six people in landslides in Acapulco Saturday. The remains of Henriette could bring heavy rains to Arizona, New Mexico, and western Texas late this week.


Figure 3. Winds of Hurricane Henriette as measured by QuikSCAT at 8:57am EDT 9/4/07. Image credit: NASA/Brigham Young University.

I'll have an update later today in all probability, after the Hurricane Hunters investigate 99L.

Jeff Masters