Thursday, September 01, 2011

Hurricane Katia and the Gulf of Mexico Blob: September 1, Update A

Yesterday I had internet issues on this other planet I’m on, so I couldn’t write anything. That’s ok though… I’m sure you enjoyed a day off and actually did something productive instead of reading my rambling thoughts. J

Hurricane Katia
Katia’s circulation improved steadily yesterday and I would agree that she’s a fully-fledged member of the Hurricane club now. Her current position is 15.2N, 45.9W, and she continues to move West at 20mph. Winds are 75mph (cat 1 range: 74-95mph) so she’s barely a hurricane according to the NHC. Her central pressure is 987mb.

Although the forecast calls for a WNW and then NW turn by late tonight/tomorrow, the large scale pressure fields are not very clear (to me) and it looks like she seems to be surrounded by high pressure at the moment with very little room to move. If that is the case, today she might slow down and remain on a westwardish track. Maybe later today I will get a better idea of the steering. I can see why the forecast has her moving NW by tomorrow – there is an area of low pressure in the Atlantic that they think will break through the high pressure and move her out that way. It is not evident in the maps at the moment though, but we’ll know by tomorrow morning whether it happened or not.

As for her intensity, I agree with the NHC…  a low-level cat 1 seems about right to me. The circulation is very strong in the lower troposphere, and it is now also good in the upper troposphere – a sure sign of a hurricane.  There is also some upper level divergence (outflow) and lower level convergence (inflow). There is also some decently strong convection near the center (all that yummy thundery red stuff in the attached satellite image of the Atlantic – she’s the red blobby area to the east of the Caribbean), although the convection is a bit fragmented outside the center – this indicates a weak hurricane.
Wind shear has increased today and you can see that in this image. It almost looks like the clouds are being blown from the west side to the east. That’s because there is some strong wind shear from the west to the east, and it is stronger on her northern side compared to the southern side. It looks like the shear will get a bit stronger today, so I don’t think she will get much stronger for now.

Gulf of Mexico Blob
You know, sometimes it seems like Mother Nature knows when I’m not looking and tries to pull a fast one. Huh. So cheeky of her!

I see we have some interesting weather in the Gulf that popped up yesterday (the red blobby area in the Gulf of Mexico in the satellite image). This has some circulation in the lower troposphere, and you can see that is has some pretty nice convection too. I am not sure if this will become a tropical storm, but I would expect strong thunderstorms and lots of rain with this blob because it is over very warm water (over 30 deg C) and a part of it is also interacting with the Loop Current which is an area of very deep warm water in the Gulf. However, like Katia, I think this is being impacted by very strong wind shear from the northwest (30-40knots) because it looks like the convection is to the east/southeast side of whatever circulation there is - it’s not a very well formed system, so it is difficult to see the circulation center. I am thinking it is nearer the TX/LA/MS section of the Gulf than the western or eastern Gulf, but the worst impacts will be on the eastern side because of the strong thunderstorms and heavy rain.  The reason I don’t think this will have a chance to get very strong is because it looks like wind shear will continue to be strong in the northern Gulf of Mexico. So this will be more water than wind.

Speaking of more water than wind, I see that the aftermath of Irene is still impacting the northern states with flooding rivers etc. What a mess! I hope power is back up for people soon, and I hope we don’t have any more overflowing banks or dams on Lakes etc.

I’ll try and write an update later today – hopefully the internet will be fully operational. Anyone want to hear about the aliens that I see walking the streets here? J


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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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