Tropical Storm Bertha Model Runs

[KWT]

The GFS ensembles will be a little further south becuase the resolution is lower and therefore probably progs an even weaker storm then the operational runs do as it doesn't have the resolution to detect the circulation quite so well. Therefore a weaker system means an even greater westerly track. Thats what I think anyway!

GFS 18z has a very weak system (tropical wave by 96hrs according to this...though you should NEVER depend on models like this for strength given they were crap with the cat-5 systems last year) so the track is even further west.

[jlauderdal]

Actually, the operational 18Z GFS' track of Bertha is slightly faster and further north when compared to the 12Z run. The west "trend" may have ended with this model.

lol...

anyway.. look at the ridge.. at 66hrs off the east coast

The ridge off the east coast means it has to go further south right?

actually a ridge would meant further left not right, .

[wxmann_91]

I wonder why the GFS is weakening it that much down the line.....Upper air charts look fairly favorable. Upper shear is 10kt or less for the most part.

well one would and has asked many times that exact question.. just look at last year the gfs did that with every system good example FELIX

The upper air pattern for Felix was simply perfect. The progged pattern for Bertha is nowhere near as favorable.

[Aric Dunn]

Actually, the operational 18Z GFS' track of Bertha is slightly faster and further north when compared to the 12Z run. The west "trend" may have ended with this model.

lol...

anyway.. look at the ridge.. at 66hrs off the east coast

The ridge off the east coast means it has to go further south right?

actually a ridge would meant further left not right, .[/quote]

yes .. farther west..
we will see at 120 hours the ridge finnaly breaks down a little as a trough lifts off to the north over new england but will have wait and see its all about timing.,.

[ekal]

The GFS ensembles will be a little further south becuase the resolution is lower and therefore probably progs an even weaker storm then the operational runs do as it doesn't have the resolution to detect the circulation quite so well. Therefore a weaker system means an even greater westerly track. Thats what I think anyway!

GFS 18z has a very weak system (tropical wave by 96hrs according to this...though you should NEVER depend on models like this for strength given they were crap with the cat-5 systems last year) so the track is even further west.

Hmm. I guess that is a possibility; I didn't think of that.

It does look like it's back to being an open wave in the model by the time it reaches the longitude of the Antilles, with a nod to the low-res arguments.

[boca]

Jlauderdale you are correct especially with a weaker system.

[Aric Dunn]

The GFS ensembles will be a little further south becuase the resolution is lower and therefore probably progs an even weaker storm then the operational runs do as it doesn't have the resolution to detect the circulation quite so well. Therefore a weaker system means an even greater westerly track. Thats what I think anyway!

GFS 18z has a very weak system (tropical wave by 96hrs according to this...though you should NEVER depend on models like this for strength given they were crap with the cat-5 systems last year) so the track is even further west.

Hmm. I guess that is a possibility; I didn't think of that.

It does look like it's back to being an open wave in the model by the time it reaches the longitude of the Antilles, with a nod to the low-res arguments.

its not the strength that matters at this point its the synoptics..

[Aric Dunn]

18z 132hr


12z 132hrs

[Aric Dunn]

entering the bahamas at 132hrs.. and still heading west.. with a decent ridge still to its north ..

[cheezyWXguy]

I wonder why the GFS is weakening it that much down the line.....Upper air charts look fairly favorable. Upper shear is 10kt or less for the most part.

well one would and has asked many times that exact question.. just look at last year the gfs did that with every system good example FELIX

The upper air pattern for Felix was simply perfect. The progged pattern for Bertha is nowhere near as favorable.

At the time, it wasnt predicted to be perfect though. The models completely overdid the hostile environment felix was forecast to pass through, however this never became the case. I dont believe this situation is the same in terms of the environment and obviously the location, however, the models maybe overdoing the shear now, as they overdid the weakness before.

[ekal]

Oh, I don't underestimate the importance of the synoptics. However, Bertha may not track that far south if it is stronger than an open wave.

[Aric Dunn]

144hr. finally a northerly turn with a trough lifting to its north..

[cheezyWXguy]

Oh, I don't underestimate the importance of the synoptics. However, Bertha may not track that far south if it is stronger than an open wave.

I agree. I dont believe it will recurve much if at all, but if it is stronger, say hurricane, then it maybe more likely to stay further north and eventually turn NW towards the end of the bermuda high, possibly threatening Bermuda or the middle east coast. But this is just my opinion. Dont take it seriously

[KWT]

Yep East Coast trough comes to save the east coast from a possible strike. IMO thats a fairly realisitic situation though the model may overestimate it outside of 96hrs as the GFS does seem to have a bias of doing that from what I've seen.

[Aric Dunn]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... loop.shtml



first trough misses it and then gfs loses it ..

[Aric Dunn]

no i see what happens the second system that is forms catches up with bertha and start interacting.. but anyway that far out but the synoptics are interesting with that ridge being strong and extending farther west ...

[KWT]

If thats the case then the whole thing is totally dependant on what the secondary system does and I wouldn't want to depend too much on that!

[Thunder44]

To those about the intensity issue on the models, I wouldn't extrapolate an open wave to a strong TS or hurricane. It's not just an issue of mininum pressure here. Once the low opens up, it doesn't show a tropical cyclone anymore.

[Extremeweatherguy]

Beyond day 4-5 there appears to be many variables that could change the track drastically. How far north/south Bertha is, how strong Bertha is, and whether or not the trough arrives in time are just a few examples. At this point, I am still leaving all options on the table. Bertha could very well slide west into Florida, bend north toward the Carolinas, New England or the Maritimes, or it could harmlessly spin out to sea. Hopefully in a few days we will be able to nail down one of these scenarios as being the most likely candidate.

[Dean4Storms]

I wouldn't be getting to carried away with what any model is doing with this beyond 3-4 days right now. Eventually if it appears to be a possible threat I'm sure the Jet will be out sampling the atmosphere and no telling what the models will respond with once they are initialized with that sampling.

Right now the best we can hope for is that shear gets her torn apart eventually which is what the GFS is probably picking up on by opening it back into a wave.