A rare triple threat: three simultaneous Atlantic hurricanes

For the first time in twelve years, we have a rare triple threat in the Atlantic--three simultaneous hurricanes. Hurricane Karl joined Hurricanes Igor and Julia in the steadily expanding Hurricanes of 2010 club this morning, becoming the sixth hurricane of the season. The last time we had three simultaneous hurricanes in the Atlantic was in 1998. That year also had four simultaneous hurricanes--Georges, Ivan, Jeanne and Karl--for a brief time on September 25. There has been just one other case of four simultaneous Atlantic hurricanes, on August 22, 1893. According to Phil Klotzbach at Colorado State, three simultaneous Atlantic hurricanes is a rare phenomena, having occurred only eight other times since 1851. The other years were 1893, 1926, 1950, 1961, 1967, 1980, 1995, and 1998.


Figure 1. Triple trouble: From left to right, Hurricanes Karl, Igor, and Julia roil the Atlantic. Image credit: NASA/GSFC.

Karl
Hurricane Karl continues to intensify. The latest Hurricane Hunter flight, flying at 12,000 feet, found flight level winds of 95 mph. This suggests surface winds of 85 mph, though the top surface winds seen by their SFMR instrument were about 80 mph. Mexican radar out of Alvarado shows the outer spirals bands of Karl are dumping heavy rains on the Mexican coast along the Bay of Campeche.


Figure 2. Afternoon radar image from the Alvarado, Mexico radar. The eye of Karl is visible in the upper right, and rain bands are affecting the coast to the east of the radar site. Image credit: Mexican Weather Service..

Forecast for Karl
Conditions for intensification are ideal in the Gulf of Mexico's Bay of Campeche, with wind shear expected to be low, 5 - 10 knots, SSTs warm, 29°C - 30°C, and the atmosphere very moist. These conditions, combined with the topography of the surrounding coast which tends to enhance counter-clockwise flow, should allow Karl to intensify into Category 2 hurricane before making landfall between Tampico and Vercruz, Mexico Friday afternoon. Karl is a small storm, and is unlikely to bring any rain or wind to Texas.

Igor
The Air Force Hurricane Hunters made their first foray into Hurricane Igor this afternoon, and found a high-end Category 3 storm, with a central pressure of 940 mb and top winds at 10,000 feet of 150 mph. The southwest portion of the eyewall was open, so Igor has the potential to intensify once again if it can close off the gap. There are no major changes to the track or intensify forecast for Igor in the latest set of model runs. Igor is expected to remain a major hurricane for the next two days, and is headed northwest at 7 mph. This motion will carry the core of the hurricane close to NOAA buoy 41044 between 9 - 11 pm EDT tonight. Top winds at the buoy so far today have been 65 mph, gusting to 81 mph, with a significant wave height of 38 feet (the significant wave height is the average of the highest 1/3 of the waves.)

Elsewhere in the tropics
The ECMWF model develops a new tropical depression a few hundred miles off the coast of Africa 2 - 4 days from now. The GFS is suggesting the eastern Caribbean could see a tropical depression 6 - 7 days from now.

I'll have an update Friday morning.

Jeff Masters