ATL: TROPICAL DEPRESSION ALEX - DISCUSSION

[KWT]

AXNT20 KNHC 212357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON JUN 21 2010

...SPECIAL FEATURES...

THE WAVE IS ACCOMPANIED BY A LARGE AREA OF DEEP LAYER
MOISTURE THAT COVERS THE ENTIRE ERN HALF OF THE CARIBBEAN
EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. BROAD LOW TO
MID-LEVEL CYCLONIC FLOW IS ABOUT THE WAVE. IT APPEARS THAT A
SURFACE CIRCULATION IS TRYING TO FORM W OF THE WAVE AXIS NEAR
14N72W SEEN IN THE LAST VISIBLE SATELLITE IMAGERY OF THE DAY.

That probably explains why the NHC decided to up it right upto 50%...if we do get a nice big burst we will probably see that go up somewhat again as thats really what its missing, a centralised region of convection.

[LSU2001]

This was posted by littlevince on page nine but seemed to get little attention. In light of a low level circulation being talked about please note the last frame on the western side. It appears that low level clouds are pulled into the center of the cloud cover.
tim

http://img197.imageshack.us/img197/9910/loopw.gif

[RL3AO]

Ship obs + me plotting the tropical wave with the L representing the possible low NHC mentioned. Sorry the image got squished a bit.

[ConvergenceZone]

Is the % chance of development something new that the TWOs are experimenting with this year? I don't remember them using that last year. I think last year they would just say, "could become a depression in the next day or two" and they would leave it at that... Unless the percentage was there, and I just missed it.

[Brent]

Is the % chance of development something new that the TWOs are experimenting with this year? I don't remember them using that last year. I think last year they would just say, "could become a depression in the next day or two" and they would leave it at that... Unless the percentage was there, and I just missed it.

Prior to last year they didn't have percents. Last year they had a range, up to 30, 30-50, or greater than 50. This year is the first year they use a specific number.

[cycloneye]

Is the % chance of development something new that the TWOs are experimenting with this year? I don't remember them using that last year. I think last year they would just say, "could become a depression in the next day or two" and they would leave it at that... Unless the percentage was there, and I just missed it.

Here are the product changes that NHC has started this season,including the % in the TWO'S.

http://www.nhc.noaa.gov/pdf/nhc_new_2010.pdf

[ConvergenceZone]

Okay thanks Brent and Cyclone.....I must have missed reading about those changes.

[CrazyC83]

At what point would they bring Recon in?

[cycloneye]

At what point would they bring Recon in?

By Wednesday afternoon if needed.

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK: POSSIBLE LOW LEVEL
INVEST NEAR 16.ON 77.0W AT 23/1800Z.

http://www.nhc.noaa.gov/text/MIAREPRPD.shtml?

[KWT]

The region they want to check tends to be a pretty good indicator as to where the NHC think the system will be.

As for percents, they have been running them in house for some time now, with some pretty impressive accuracy levels at times.

Also, thanks for the image RL3AO

[ozonepete]

New here, guys/gals. Be polite! LOL. I have meteorological background and look forward to great discussions. Enough of that. Here's my first post. It appears as though our blob is trying to develop a closed circulation. See image below.

Welcome to storm2k! Thanks for your contribution of the multi-platform wind analysis from Colorado State RAMMB. We use a lot of their analyses here at storm2k - they make invaluable contributions to hurricane research.

Hurakan showed us some of the science behind that image, but just for everyone else, it is a sophisticated blend of 4 different scatterometry satellite images, most of which we've already seen. You can see the 4 images that went into Ikester's image here:
http://rammb.cira.colostate.edu/products/tc_realtime/mpsatwnd_image.asp?storm_identifier=AL932010&mpsatwnd_filename=2010AL93_MPSATWND_201006220000

It uses AMSU-A brightness temperatures (we use them from CIMSS here) that are extrapolated to 850mb in the upper left
Cloud-drift winds in the upper right
IR satellite derived winds in the lower left
ASCAT winds in the lower right

Although it uses derivations for its results, these charts are the result of a lot of hard work from RAMMB and will probably prove to be very useful to us. Thanks for pointing it out. And again, welcome.

[HURAKAN]

Vorticity increasing



Convergence is good too

[ronjon]

There is weak cyclonic turning near 14.5N-68.7W. Probably mid-level at this point. I don't think it'll do much tonight due to the dry land breezes inflowing off SA which should limit convection.

http://www.ssd.noaa.gov/goes/flt/t1/flash-rgb-s.html

[ozonepete]

There is weak cyclonic turning near 14.5N-68.7W. Probably mid-level at this point. I don't think it'll do much tonight due to the dry land breezes inflowing off SA which should limit convection.

http://www.ssd.noaa.gov/goes/flt/t1/flash-rgb-s.html

That's what I see. I got 14.7-69.0, and I like using the rgb at night as well.

Not sure land breezes would be important here, though. They would be too local in reach.

[ronjon]

Not sure land breezes would be important here, though. They would be too local in reach.

I'm talking about inflow from the south which would feed the storm. It's essentially limited by continental dry air of SA. Air currents from a large land mass has less moisture and will lead to greater subsidence.

[Dean4Storms]

There is weak cyclonic turning near 14.5N-68.7W. Probably mid-level at this point. I don't think it'll do much tonight due to the dry land breezes inflowing off SA which should limit convection.

http://www.ssd.noaa.gov/goes/flt/t1/flash-rgb-s.html

That's what I see. I got 14.7-69.0, and I like using the rgb at night as well.

Not sure land breezes would be important here, though. They would be too local in reach.

Agree, just not sure if that is a surface rotation or a mid level.

[Florida1118]

More of the 8pm computer models seem to be moving the system closer to Florida if it develops.

[ROCK]

More of the 8pm computer models seem to be moving the system closer to Florida if it develops.

they were left this am and right this evening. Wait for the LLC and then the models should show more consistency....

[Hugo1989]

Este sistema 93L si llegara a ser una depresion tropical para el informe de las 2:00pm de manana. No hay manera que este sistema corra la misma suerte que el 92L. Cual es su impresion de tener 2 sistemas en el pacifico y dos areas en desarrollo en pleno mes de junio??? las antillas mayores sufriran el azote de un sistema, sea tormenta o nivel huracan. en especial Cuba y Puerto Rico.... veo un comienzo de temporada muy irregular y preocupante!!

[Cdeck81]

Could we see a code red at the 2 AM updated?