ATL: TROPICAL DEPRESSION ANA (02L)

[jinftl]

Models splitting into 2 camps....both avoid major landmasses

[Derek Ortt]

I am also seeing shear from the UL over the system and a restriction of the outflow

[Air Force Met]

I do see the outflow flattening out on the western side of that loop, AFM. Sure does look like shear increases as it moves westward.

http://www.ssd.noaa.gov/goes/east/tatl/flash-wv.html

OVerlay the HDW-H.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/06/images/gfs_200_006l.gif

Not really any shear out there. Its underneath anticyclonic flow (see 200 mb chart)...all the way to the islands. In a couple of days...it will face some more shear...but again...its easterly shear.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/06/images/gfs_200_048l.gif

[wxman57]

LOL @NHC Ah-na is finally here. Forecast track is interesting. Better not hit land, or the intensity forecast is gonna be wrong.

Just pretend you're Ahnold when you say it.

[Sanibel]

Textbook horizontal shear or (subsidence).


Struggling weak depressions are much more vulnerable to dry airmasses.

[HouTXmetro]

Assuming it survives I'm just puzzled at latest guidance. This could potentially miss CONUS all together and be Mexico Central American storm. Of course it appears the Islands and key's will be affected in some shape form or fashion.

[wxman57]

I do see the outflow flattening out on the western side of that loop, AFM. Sure does look like shear increases as it moves westward.

http://www.ssd.noaa.gov/goes/east/tatl/flash-wv.html

OVerlay the HDW-H.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/06/images/gfs_200_006l.gif

Not really any shear out there. Its underneath anticyclonic flow (see 200 mb chart)...all the way to the islands. In a couple of days...it will face some more shear...but again...its easterly shear.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/06/images/gfs_200_048l.gif

That assumes the GFS was initialized correctly. I've seen it do pretty badly over the oceans. The WV loop clearly shows the western outflow restricted now.

[sponger]

I would not worry to much if I was in S FL. Even if Anna survives everyone knows the safest place to be 5-6 days out is right down the center of the cone!

[Frank2]

Still way too early to say it's coming this way, since the GFS shows only a modest ridge that steers Ana back towards Florida, and at a much slower rate that the official NHC forecast plots:

http://weather.unisys.com/gfsx/loop/gfsx_500p_loop.html

Andrew, on the other hand, was steered by a very strong ridge (1032 mb, if I recall) that built to it's north, so the current situation is very different, as they all are...

Frank

[JPmia]

http://www.sun-sentinel.com/news/weathe ... 3205.story

Well the good thing is we have plenty of time to stew over it...it's now a top story in this morning's news.

[Sanibel]

Folks may want to look a the wave in the FL Straits for some "hints" of future tracks regarding Ana. The ridging and potential EC trough will effect that wave much sooner than Ana. Just my 0.02 cents worth.

Keen observation. I was going to post the same thing.


We'll have to see from the guru's what the synoptic is going to do before Ana gets there.


Any run over the islands will rip up this weak system.

[jinftl]

True!

I think the key will be....does she get ripped apart by land (Hispanola, Cuba) or does she stay north of that. What is always a little scary about storms approaching florida is that they can be strengthening up until landfall.....and can even receive a last minute steroid shot from the Gulf Stream

I would not worry to much if I was in S FL. Even if Anna survives everyone knows the safest place to be 5-6 days out is right down the center of the cone!

[otowntiger]

Models splitting into 2 camps....both avoid major landmasses

Yeah, but when the models evenly split like that, then the usual chosen prediction by the NHC is down the middle which would take it down the spine of Hispanola, virtually assuring dissapation. However I see that the NHC is keeping her just north the largest landmasses. Right now the main issue with Ana is surviving the apparent prohibitive environment in the form of shear and extremely dry air.

[Air Force Met]

I am also seeing shear from the UL over the system and a restriction of the outflow

I see no evidence of it in the WV...the HD winds...the shear charts or the UL charts.

Is the upper level environment ideal? No way. But...its certainly not shear that is causing convection to be scattered.

I know the NHC says some westerly vertical shear...but I see no evidence of it. I know how to read a satellite and I see cirrus and mid clouds moving westward away from the center.

Point is this. Even if there is some undercutting shear there somewhere (and again...I see no evidence of it...please show me the frame and movement)...it is NOT enough to cap convection and produce tops that are only -50C at best. It has ingested dry air...and you can see how dry it is to the SE where there is absolutely no CU. On a vis you can see cirrus moving west over the center....and moving SW south of the center. But its bone dry to the south where the southerly inflow is.

Now...I mow my yard.

[Sanibel]

The season hasn't quite worked out the negative conditions or else this would be a very dangerous track if it went north of the islands.

[gatorcane]

well as I stated last night, why even upgrade this system? My vote was to wait until today to see how it looked as I knew dry air would get to it.........90L should have been upgraded last night instead.

Looks like Ana may just get downgraded again sometime this weekend, maybe become a remnant low again and my thought is that cone keeps getting shifted south little by little. I can see this passing south of Florida as a remnant low, strong wave. I'm really not too worried about this thing for us here in South Florida.

[Pearl River]

If I remember correctly, and the Pro's can help with this, the weaker storms are not affected as much by Hispaniola and Cuba. It's the stronger storms where the circulation gets really disrupted and they have a harder time coming back.

[jinftl]

Current wind probabilites (11am Saturday Advisory)

Watch the trends on these numbers with each advisory....change from prior advisory (5am) in ( ):

Fort Pierce
34kt 10% (0)
50kt 4% (+1)
64kt 1% (0)

West Palm Beach
34kt 11% (+2)
50kt 3% (0)
64kt 1% (0)

Miami
34kt 11% (+1)
50kt 4% (+1)
64kt 1% (0)

Marathon
34kt 9% (+2)
50kt 4% (+4)
64kt 1% (+1)

Key West
34kt 9% (+3)
50kt 4% (+3)
64kt 1% (+1)

[Air Force Met]

I am also seeing shear from the UL over the system and a restriction of the outflow

And one more point before I mow my yard (see...I really don't want to get outside when its 90F at 10 AM)...

If storms were so delicate as to lose there convection in the face of this amount of "shear"...we would never get a storm. That's why I am saying it has to be something else. Every system...at some point...faces less than ideal upper air...worse than this...and most of them can muster colder than -50C over the tropics.

The tops began to warm before it moved out...and even in shear...storms muster colder than -50C.

It has to be dry air that is causing warm tops...and the fact the convection is scattered...and the cu field to the sw-se is gone. There is no moist inflow into the system.

[wxman57]

I am also seeing shear from the UL over the system and a restriction of the outflow

I see no evidence of it in the WV...the HD winds...the shear charts or the UL charts.

Is the upper level environment ideal? No way. But...its certainly not shear that is causing convection to be scattered.

I know the NHC says some westerly vertical shear...but I see no evidence of it. I know how to read a satellite and I see cirrus and mid clouds moving westward away from the center.

Point is this. Even if there is some undercutting shear there somewhere (and again...I see no evidence of it...please show me the frame and movement)...it is NOT enough to cap convection and produce tops that are only -50C at best. It has ingested dry air...and you can see how dry it is to the SE where there is absolutely no CU. On a vis you can see cirrus moving west over the center....and moving SW south of the center. But its bone dry to the south where the southerly inflow is.

Now...I mow my yard.

I agree, dry air is a problem, too. NHC mentions the very shallow vertical extent of Ana (only to 500mb). I do see shear impacting the western side of Ana. Looking closely at the WV loop, it may be affecting Ana in the mid levels vs. the top. I can see the bright cirrus isn't deformed as much as the middle layers. Both may be players in the weakening.

I'm going for a 4hr bike ride, then I have to mow my lawn. Can you mow my lawn, too, while you're at it?