12 and 18Z GFS BOGUS!

[PurdueWx80]

I don't have the time or means to do an in-depth scientific discussion and comparison of models at the moment; however, 12-hour and 6-hour verification at 00z from the 12z and 18z runs, respectively, of the GFS is quite poor. In other words, the GFS has no idea what Dennis is doing.

The 12z run of the GFS 12-hour forecast valid at 00z:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_012l.gif

and the 18z valid at 00z this evening:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_006l.gif

The X marks the location of the center of the storm (the eye). The storm is about to brush the Ensanada de la Broa (the large bay on the south side of the island) per radar imagery from Key West: http://www.srh.noaa.gov/radar/latest/DS ... kbyx.shtml

GFS errors here, even from only 6 hours out, are horrendous. The storm is not moving between NW and NNW as the model suggested, but closer to WNW. I'll attribute this to interaction with Cuba's mountainous terrain but it could just as easily be an inappropriate measure of the ridge to the north of the storm, among other things. If the current WNW motion continues until the storm clears Cuba, some major shifts west will have to be made by the NHC since they have been closely following the GFS and it's suite of hurricane models.

AS a side note, the "bogus" 12-hour forecast from the 12z run of the NAM is nearly spot-on at 00z:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_012l.gif

[deltadog03]

You need an award...seriously...IF** this keeps moving this way...NHC might sh** there pants...lol

[gkrangers]

Yeah...I don't quite see Dennis hugging the west coast.

It has a sustained WNW movement now, not a wobble. The ridge is not weakening.

Is there a shortwave over LA/MS right now? What impact will that have?

[gkrangers]

You need an award...seriously...IF** this keeps moving this way...NHC might sh** there pants...lol

Why..the NHC track is generally verifying so far.

[jabber]

I don't have the time or means to do an in-depth scientific discussion and comparison of models at the moment; however, 12-hour and 6-hour verification at 00z from the 12z and 18z runs, respectively, of the GFS is quite poor. In other words, the GFS has no idea what Dennis is doing.

The 12z run of the GFS 12-hour forecast valid at 00z:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_012l.gif

and the 18z valid at 00z this evening:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_006l.gif

The X marks the location of the center of the storm (the eye). The storm is about to brush the Ensanada de la Broa (the large bay on the south side of the island) per radar imagery from Key West: http://www.srh.noaa.gov/radar/latest/DS ... kbyx.shtml

GFS errors here, even from only 6 hours out, are horrendous. The storm is not moving between NW and NNW as the model suggested, but closer to WNW. I'll attribute this to interaction with Cuba's mountainous terrain but it could just as easily be an inappropriate measure of the ridge to the north of the storm, among other things. If the current WNW motion continues until the storm clears Cuba, some major shifts west will have to be made by the NHC since they have been closely following the GFS and it's suite of hurricane models.

AS a side note, the "bogus" 12-hour forecast from the 12z run of the NAM is nearly spot-on at 00z:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_012l.gif

Nice update... thanks. You would think they could get the initilzation correct. that seems pretty easy to me.

[deltadog03]

It has done pretty good...i take that back...IF** this motion continues...and they don't update it at 11p..then i will repeat the statement...thanks for pointing that out

[gkrangers]

It has done pretty good...i take that back...IF** this motion continues...and they don't update it at 11p..then i will repeat the statement...thanks for pointing that out

Yeah, if the WNW motion continues..theyll have to adjust slightly west, but I don't think dramatically.

Definitely a bad sign for SE LA tho...

[LilNoles2005]

Yeah...I don't quite see Dennis hugging the west coast.

It has a sustained WNW movement now, not a wobble. The ridge is not weakening.

Is there a shortwave over LA/MS right now? What impact will that have?

I think a lot of the current movement of Dennis has to do with land/sea/mountain interaction.

The WV loop looks pretty interesting to me, but I am an amateur.

[x-y-no]

Yes ... I think we're getting the answer to the question of whether the problems the GFS exhibited last year (steering strong storms north into ridges) has been cured. Unfortunately, the answer seems to be in the negative.

Jan

[Steve]

Thanks Purdue. It will be interesting to see how the errors play out down the line. Bust out a post or two if you uncover anything else.

Steve

[clfenwi]

Yes ... I think we're getting the answer to the question of whether the problems the GFS exhibited last year (steering strong storms north into ridges) has been cured. Unfortunately, the answer seems to be in the negative.

Jan

It hasn't been displaying the problem as consistently as it did last year. You may remember how at one point during Ivan it wanted to turn him northeast to the Bahama... for the entire duration of that storm GFS was on the eastern edge...

That wasn't the case this time. Up until two days ago, GFS' track was more on the western side of the envelope. That changed once the Gulfstream IV flights started.


Comparing the 12Z models at 00Z... GFS is too far east... UKMET and NOGAPS too far west; too much time over water ... CMC looks to be in the best shape of the four.

Compare:
http://moe.met.fsu.edu/cyclonephase/gfs ... 812/5.html
http://moe.met.fsu.edu/cyclonephase/ukm ... 812/4.html
http://moe.met.fsu.edu/cyclonephase/ngp ... 812/5.html
http://moe.met.fsu.edu/cyclonephase/cmc ... 812/4.html

[clfenwi]

A tidbit from HPC's model diagnostic discussion this afternoon (1:36 PM EDT)

...HRCN DENNIS...

IN THE GFS... APPARENT FEEDBACK FROM CUBA INTO FL MAY BE PULLING
ITS SFC LOW TOO FAR EWD DURING TONIGHT INTO SAT BEFORE RETURNING
CLOSER TO CONSENSUS FROM F36 LATE SAT ONWARD. OTHERWISE THE GFS
APPEARS TO OFFER A TRACK THAT IS CLOSER THAN OTHER GUIDANCE TO THE
TPC/NHC TRACK AS GIVEN IN THE 1500 UTC ADVISORY. AMONG THE LATEST
MDLS... THE NAM IS THE LEFT-HAND OUTLIER AND SHOULD PROBABLY BE
GIVEN VERY LITTLE WEIGHT GIVEN ITS TYPICAL DIFFICULTY WITH
TROPICAL SYSTEMS AND LESS THAN IDEAL INITIALIZATION. THE 12Z
CANADIAN GLBL TRACK IS NOT FAR FROM THE GFS BUT A TAD FASTER...
AND THE UKMET/00Z ECMWF ARE SLIGHTLY LEFT OF THE GFS.