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A rare triple threat: three simultaneous Atlantic hurricanes

By: Dr. Jeff Masters, 8:47 PM GMT on September 16, 2010

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.

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.

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


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Quoting RitaEvac:
I've got bad news for a lot of people

Quoting JamminNJ:
Any webcams in the Veracruz area? Looks like Karl is paying them a visit right about now...

This one is supposed to show a view of the city... Looks pretty nasty...


Would this be the final moments of Julia, Dry air surrounding her....??
Quoting sunlinepr:

Would this be the final moments of Julia, Dry air surrounding her....
The dry air didn't do her in, Igor did.

30-40 knots of shear will rip a storm apart VERY fast.

Maybe if you're comparing a mobile home to the pre-1992 era, non-brick, shoddy contractor conventional home.

If you're comparing them to what "good" contractors always made, or to what the minimum post-Andrew code is, then no. Mobile homes are not even close.

I've even seen demonstrations on television where a pair of jet engines operating at 150mph from a distance of around 100ft, can blow away an anchored mobile home after just a few seconds to a minute of exposure.

Now by the time you figure the engines only affect a fraction of the surface area of the building, the net equivalent wind force on the anchored mobile home was probably only the same as category 1 sustained winds would be across the entire windward side.

So basicly a mobile home, even when anchored, is completely destroyed somewhere around sustained category 1 or 2 force winds, after just a few minutes of exposure.

Whereas even a pre-1992 era conventional home doesn't suffer "complete roof failure" until around 115mph sustained.

A conventional home that is completey wrapped in plywood (like my dad always did anyway,) and has the hurricane straps installed can survive even more than that.

Now I'm not entirely up to speed on what the codes are since Katrina, but I will say that even post-1992 homes were often built to the minimum that the contractor can get away with to get the inspector to pass, which often did not require a complete wrapping of plywood. So many houses have absolutely nothing but a layer of vynl siding on top of a half inch of polystyrene insulation, plus the drywall on the inside. Now this "light" sheet form of polystyrene is actually so weak you can break it accidentally just by turning too quickly as you carry it, so it offers ZERO protection from impact. While drywall is so fragile you can put your fist straight through it and not injure yourself. In short, if they were hit by a 50mph projectile it probably would go straight through, and I have no doubt that a 100mph projectile would hardly even be slowed down by a post-1992 non-brick home's exterior wall.

That being said, the mobile home will be completely un-anchored and destroyed by the windforce alone, long before the post-1992 home suffers anything more than cosmetic damage.
Ok, seems like the last moments to go....

Quoting jeffs713:
The dry air didn't do her in, Igor did.

30-40 knots of shear will rip a storm apart VERY fast.
Looks like karl is going to make landfall just south of the laguna verde nuclear plant, putting it in the worst part of the storm. Hope that plant was built strong.