Thursday, September 12, 2013

Tropical Storm Gabrielle, Hurricane Humberto, Tropical Depression 10, and the sound of interstellar space!: September 12, Update A

Bravo to all those who worked on Voyager. What an awesome achievement! As a tribute, this entry will be out of this solar system and we will boldly go where no spacecraft has gone before. By the way, have you heard the sound of interstellar space yet? If not, listen here: I think the translation so far is: “People of Earth, your attention, please. This is Prostetnic Vogon Jeltz of the Galactic Hyperspace Planning Council.” Great. The first interstellar contact and it’s a planning council?? Really? Hmm… I wonder what they want? ;-) (HGTTG)

Tropical Storm Gabrielle

Meanwhile, here on planet Earth we have Hurricane Humberto, Tropical Storm Gabrielle, and Tropical Depression 10. You can see all three of them in this IR satellite image of the Atlantic:

What do you mean you can’t see three? Look again: Humberto is on the left, Gabrielle is close to the northern edge of the image, and TD10 is over Mexico. Still can’t see Tropical Storm Gabrielle? Hmm. Apparently the NHC can see her quite clearly. Well let’s look at the circulation shall we? Surely she must have as much, if not more, circulation than a Tropical Depression?

<Science Alert!> As I mentioned a couple of months ago, the troposphere is the lowest level of our atmosphere ( Any type of stormy weather has a defined vorticity (circulation) signal in the troposphere. Low pressure fronts look different compared to tropical storms. You can tell how strong a tropical storm is depending on how strong the vorticity is, and how high into the troposphere that signal can be seen. A Tropical Storm ALWAYS has a vorticity signal that reaches the middle of the troposphere (around 500mb) because this indicates that there is some deep convection (big thundery clouds). <End Science Alert!>

This is an image that represents the vorticity (circulation) in the troposphere (from the University of Wisconsin):

These plots are a little tricky to interpret so don’t think that all red patches are tropical storms, because they aren’t. But you can easily see Humberto on the left. A nice, strong round signal – pretty strong middle-troposphere circulation which is what you would expect for a Hurricane. There’s TD10 just hanging onto the southern Gulf of Mexico – not as well defined as Humberto and not a contained blob, so really not a Tropical Storm, but there is a bit of red so there is something there. But Gabrielle!! <Rant Alert!!> It’s blue!! BLUE!! That means there is NO deep convection in this storm… there is no way this is a Tropical Storm!! I can’t believe someone thought it was and renamed it!! NO convection, NO circulation!! What were they thinking?!?! In that case, we have stronger ‘Tropical Storms’ over Florida on an almost daily basis!! Oh, maybe those clouds in the middle of the Atlantic should have names too while we’re at it! Wow!!.....!!!!!!!!!!!!!!!!!!!!!! <End Rant!>

She’s officially supposedly at 35.1N, 67.7W, moving NNE at 10mph, winds are 40mph (very weak), central pressure 1008mb.

And that’s all I have to say about Gabrielle. Harumph. And ner.   

Hurricane Humberto

As badly mis-diagnosed as Gabrielle is, the NHC are on track with Humberto. Not only does he have convection (see satellite image above) and circulation in the middle of the troposphere as you’ve seen, but he also has a signal in the upper troposphere:

Although the dry air and wind shear is taking its toll today, the NHC estimate his wind speed to be about 80mph, central pressure 984mb. This makes him a weak-to-mid-strength cat 1 (range: 74-95mph). He is at 23.4N, 29.7W, heading NNW at 12mph. All this looks groovy to me. No rants required. I agree with the NHC forecast track of continued northward movement and the gradual turn to a more westward movement in 24 hours. I also agree with a gradual weakening, and it is quite possible that he’ll be a very weak cat 1 or a very strong Tropical Storm by this time tomorrow.

Tropical Depression 10

Again, you’ve seen that this blobette has some circulation in the middle troposphere, but it doesn’t have that well-contained area of vorticity that we see with a storm, which means it doesn’t quite have to right structure to be a tropical storm yet. She is also interacting with land and has some wind shear, so I’m not sure it will get to tropical storm status unless it moves farther into the Gulf. There is certainly a large area of convection, but that is because she is interacting with some very warm waters – the sea surface temperatures in the Gulf are over 28 deg C, with water warmer than 26.5 deg C in the upper 75-100m in some parts.   

I’ll be back again with more on some of these storms tomorrow. In the meantime, I see there has been some flooding in Colorado… from fires to floods all in one year!! Stay safe out there my peeps!


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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.

1 comment:

Sarah Kivi said...

Just as a safety measure I have readied my favorite towel.