Tuesday, September 12, 2006

"Hurricane" Florence, Tropical Storm Gordon & Tropical Depression 8: September 12, Update B

One...too...many... storms....too...much... to...talk...about.
Just skip to the one you are interested in (but I wrote this so it
*must* be a fascinating read ;) ) ...

Also... in case you fall asleep by the end... TD8 is the one to keep one
eye on as far as we are concerned - although there is a chance it will
also recurve out to sea. But it's not yet even a TS yet.

"Hurricane" Florence:
This is no longer a tropical system because it is over colder waters now
and the interaction between the ocean and atmosphere is not the same, so
it is now an extratropical system. Winds are "near 75mph" and this is
still a big storm (in size). Cloud tops are very warm, there is dry air
all around the eye, there is huge wind shear etc. The NHC are no longer
putting out advisories on this system after the 5pm advisory today.

This is the sort of storm that meteorologists argue over whether or not
to even call a hurricane because the physics that maintain this sort of
system is very different from a tropical system. Therefore the
"hurricane" classification is based on wind speed alone, which is a bit
dodgy in my humble opinion. :)

This also highlights one of the many problems with the historical record
of hurricanes - in the old days this wouldn't be classified as a
hurricane. However, in more recent times the way storms are defined has
changed. Fortunately a project is currently underway to try and bring
the historical hurricane database onto a more even platform (there are
many many other problems with the database in addition to this one).
After that is done (sometime in the next year or two hopefully), then
studies that look at changes in hurricanes (e.g. intensity) over the
past x number of years will have a more solid footing on which to base
their claims.

How many paragraphs can I start with the word 'This'?

Bye bye Florence.

Tropical Storm Gordon:
As I said earlier, TS Gordon has colder cloud tops than Florence. I
should explain that colder cloud tops means that the clouds are 'deeper'
and there is more convective activity. In the troposphere (the layer of
the atmosphere closest to the ground, the temperature gets colder with
increasing height - think of climbing a mountain and how it is colder
the higher up you go). I could actually work estimate how much higher
the tops are compared to Florence, but that might just throw you all
over the 'science threshold' (and in case you haven't figured it out by
now, yes, I'm a science geek and proud of it). :)

It has become better organized since I looked at it earlier in the day.
But it is still a TS. Sustained winds are 65mph, so some intensification
since earlier. It is heading due north, but not very quickly at a mere
7mph. Over the next 24 hours the ocean conditions are good for some more
intensification, the wind shear is low, and I don't think dry air will
be a player for now. This will probably be a hurricane by this time
tomorrow. But not a cat 2. One of the models has it as a cat 2 in three
days. This model has been over-intensifying storms all season as far as
I can remember. The NHC seem to have picked up on this and are placing
less emphasis on it as they did at the beginning of the season, so the
NHC forecast has the intensity as a strong cat 1 in 2-3 days. I think
this is far more reasonable.

TD 8:
Hot off the coast of Africa, this system is not even a TS and I can see
the center of circulation. The good news is that it is heading into an
area of higher wind shear. The bad news is that it is in an area of lots
of atmospheric moisture... hardly any dry air in sight. It's moving
westward at 15mph. Sustained winds of 35mph (TS=39-73mph). Temperatures
are 28 degs C, and on its westward path it will soon (24-36 hours) get
to 29 degs C temps. So I expect some intensification over the next 24-36
hours. This will be TS Helene (I had to look that up :) ).

Current model track forecasts have it remaining far north of the
Antilles. It's too soon to tell I think.

Stay tuned for more tomorrow ...

These remarks are just what I think/see regarding tropical storms (my
storm blog). If you are making an evacuation decision, please heed your
local emergency management and the National Hurricane Center's official
forecast. This is not an official forecast.

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