Thursday, September 08, 2011

Hurricane Katia, Tropical Storms Maria and Nate: September 8, Update A

Today is a big day. It is the 45th anniversary of Star Trek. The <whisper>third<whisper> best sci-fi tv show ever. (Shhhh… I have to whisper because I suspect there are one or two Star Trek fans reading this…don’t tell them, but the top two are Blake’s 7 and Dr. Who ;-)). Happy Birthday Star Trek!

It is also a big day because there are three storms out there now. Nate has grown up since yesterday. He broke away from his low pressure front home and is now standing on his own two storm feet. He’s not yet learned to walk on them though, so he’s still tottering around over the Bay of Campeche. More on Baby Nate later.

Hurricane Katia
She’s pretty well behaving as expected. All day today she’s been a cat 1 (range: 74-95mph) and is following the forecast track. She’s currently at about 36.3N, 68.8W moving NE at a rapid speed 21mph. Officially wind speeds are currently 85mph (mid-level storm), central pressure is 973mb. There is really not a lot of convection in this system so I expect she’s a weak cat 1 by now, but I’ll go with the NHC on this one.

On Bermuda, Steve says: “It’s windy but not so much to raise an eyelid. We have cloudy skies, low humidity and mid 20dC. Sparkling weather!”

Time for another round of golf to celebrate? ;-)

There’s not much more to say about Katia for today. She’ll move NNE then NE, towards the UK. She’ll remain a cat 1 for now.

Tropical Storm Maria
Like the song says, Maria is a Williow the Wisp. She weakened earlier today and now officially has winds of 40mph, central pressure 1005mb. Winds that low suggest she is barely a Tropical Storm. She also continued westward rather than take that WNW/NW turn. She’s at 13.2 N, 53.6W moving rapidly W at 21mph.

The forecast track still has her making a WNW turn, but it has shifted south so now she’ll enter the Caribbean and pass south of the VIs on Saturday. From what I am seeing that high pressure to her north is still holding steady which suggests to me that she’ll carry on a more westward track tomorrow as well.

She is really a messy little storm! I can’t see her center of circulation and will go with the NHC on this. Convection has increased a bit because she is moving over warm waters, but the circulation is weak in the middle levels of the troposphere and there will continue to be some wind shear. It’s unlikely that she will get much stronger before she gets to the Lesser Antilles.

Tropical Storm Nate
As I mentioned earlier, he grew up into a proper Tropical Storm today and I can talk about him now. Phew! ;-)

They sent a plane in today to get his measurements and officially he’s at 19.7N, 92.2W, and is stationary. Wind speeds are officially at 70mph, central pressure is 994mb. The forecast models still have him going all over the place.

The reason he is stationary is because he is surrounded by high pressure. You can imagine him being stuck in a well and until the walls are broken he won’t be going anywhere. Being stationary makes the forecast track for any storm even more difficult than usual, which is why the models can’t agree at the moment. There are a couple of things that are confusing the track forecast for Nate:
1. He is stationary. The longer he remains in one place, the more the surrounding pressure fields have a chance to adjust around him, so when he does get going things might be different.
2. He is a messy storm. I can’t see where the center is actually, so I will have to go with the NHC and the plane fix, but I am not 100% convinced that his center is at that location. I think he is a bit farther south, and may already be interacting with Mexico.

His convection has decreased a lot in the past few hours – you can see this in the latest IR satellite image:

His vorticity (circulation) has also deteriorated. This suggests he is struggling. But wind shear is very weak and water temperatures are warm, so I think it must be interaction with land that has caused him to deteriorate.  I don’t think the winds are as strong as 70mph, and I would classify him as a weak-to-mid level Tropical Storm.

Now for something completely different…
Hey new readers! Welcome. I know a bunch of new people started reading this recently. First, I’m sorry and are you sure? ;-) Second, I’ve been explaining all sorts of fascinating jargon and wonderful sciencey stuff throughout the season so if I use a word that is new to you, you have two choices… you can either scroll through the ~15 billion updates I’ve had to write this season and see if you can find the jargon explanation… or you can send me a question asking for clarification. I can’t promise that you’ll go away any more enlightened, but there’s no harm in trying, right? ;-)

That’s it from me in Savannah. I’ve been here a few times, and it is still a charming city to visit. Clay from Georgia sent me this delightful description: “Savannah is a charming old dowager, like the old widow who lives alone in the weathered mansion, probably haunted, but lovely.” J


Blogs archived at
Twitter @JyovianStorm

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.

No comments: