Sep 1, 2011

DAY 92

At 11pm eastern, Katia was upgraded to our 2nd hurricane in the Atlantic this season. She has estimated sustained winds of 75 mph with a central pressure 987 mb. Judging by her structure and her deep pressure, she is likely a stronger hurricane than she is being listed as right now.

(Hurricane Katia)
The Hurricane Center is forecasting Katia to continue moving WNW over the next 5 days, becoming a major hurricane this weekend. This track would keep Katia well to the north of the Antilles Islands.

The computer models are in agreement with keeping Hurricane Katia away from the Antilles. A few of the models today displayed a curious westward movement to Katia at about day 5. In this GFS freeze frame below. there is a small tropical disturbance to the southeast of Katia. When 2 tropical systems exist within a close proximity to each other, they have a towing effect on each other. The system to the west feels a southward pull and the system to the east feels a northward pull. This is called the Fujiwhara Effect, named after the scientist that discovered it in 1921. That system is likely too small to have a great effect on Katia, which will likely be a major hurricane at that time. This is bad news however for Bermuda, as this would mean they could get the business end of Katia as she passes to the west of the Island.

The steering layer at the moment shows a massive gap in the central Atlantic between 2 ridges. This is the most overwhelming evidence that Katia will stay on that WNW heading.

Also today, the Hurricane Center has designated that area in the Caribbean as Invest 93L, and is giving it a 60% chance of developing into a tropical cyclone in the next 48 hours. You can see a very busy Gulf of Mexico right now. The tropical wave is just entering the southern Gulf between Cuba and the Yucatan, there is also another trough axis from an old frontal boundary laying across the central Gulf, and there is some wind shear from the west that is helping to fire up a lot of convection in the area. There is however no real visual evidence of any organized rotation.

(Invest 93L)

This Invest is likely to become Tropical Storm Lee however. The computer models have no idea what this system is up to yet. For one there is no surface low to focus in on yet. And two, there is a lack of steering currents in that area right now, so this system will go basically wherever it wants. One thing we do know for sure is that the high pressure system that's been over Texas all season, is still there and not moving. That is naturally where this system will want to go, so with that ridge throwing a block on it, that will likely mean the system will just stall out and fester in the Gulf for several days. This is a recipe for a growing tropical cyclone to become a storm of even a hurricane.

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