2017 Global Model Runs Discussion (Out to day 16)

[gatorcane]

That massive High over nearly the entire Eastern 2/3 of the CONUS made little sense for this time of year. No surprise the models are backing off and showing less ridging.

Interesting the GFS is honing in on a solution a bit more the last few runs but the Euro did something drastic on the last 12Z run moving away from a Central GOM solution after showing this for several runs in a row. The GFS wants to develop a low in the SW Caribbean and move it north while developing it further - makes a lot of climatological sense.

Needless to say a lot of uncertainly on what happens in the Western Caribbean. The ensemble forecasts should prove more useful than operational guidance.

With La Nina and extremely warm SSTs needs close monitoring.

[gatorcane]

12Z ECMWF ensembles (animation from hour 144 to 240) generally show a turn north in the NW Caribbean with several turning NE near Western Cuba or SE GOM. Typical October track:

[gatorcane]

12Z GFS wind shear looks highly favorable near Florida in the long-range:

[LarryWx]

This post I'm about to make is not about 99L nor the potential W. Caribbean genesis of about a week from now. This is regarding the in between period 10/4-7, during which both the 12Z EPS and 12Z GEPS have a few members form a low underneath the big high offshore the SE coast and then move them onshore between Daytona and Charleston within 10/4-7. Four EPS/GEPS members get to under 1004 mb while two of the EPS get to sub 1000 mb/one to sub 992 mb while one GEPS gets to sub 1000 mb.

Based on the small number of members having this as well as the projected shear, this will likely not ever amount to a big deal. However, there appears to be small possibility of something nontrivial forming and the steering would be toward the SE US underneath the big high. This seems to be related to the 2nd microlow that had been on several earlier Euro runs.

[gatorcane]

I think we decided for the long-term Western Caribbean system we can use this thread. For the system near Florida NHC has marked, the other thread (99L).

[LarryWx]

I think we decided for the long-term Western Caribbean system we can use this thread. For the system near Florida NHC has marked, the other thread (99L).

Hey gator,
Agreed 100%. I can't tell if you were responding to my post, but in case you were, my post is about a different potential system from 99L and the W. Caribbean system, and I was not responding to your prior post. I was trying to say that my post was about neither.

[gatorcane]

I think we decided for the long-term Western Caribbean system we can use this thread. For the system near Florida NHC has marked, the other thread (99L).

Hey gator,
Agreed 100%. I can't tell if you were responding to my post, but in case you were, my post is about a different potential system from 99L and the W. Caribbean system, and I was not responding to your prior post. I was trying to say that that post was about neither.

Gotcha OK, makes sense.

[LarryWx]

I know it is the 18Z GFS, my "favorite" run lol, but like the 12Z GFS, it gives FL a big blow with a strong TC hit on S FL on 10/7.

The period 10/7-10 was suggested by the 3 main 12Z ensemble runs to be the period FL is at highest risk from getting a hit from below.

[gatorcane]

222 hours:

[DESTRUCTION5]

I know it is the 18Z GFS, my "favorite" run lol, but like the 12Z GFS, it gives FL a big blow with a strong TC hit on S FL on 10/7.

The period 10/7-10 was suggested by the 3 main 12Z ensemble runs to be the period FL is at highest risk from getting a hit from below.

That's 2 in a row.....1st time I saw GFS show same scenario in 7-10 day in back to back.

[SFLcane]

Yikes Gatorcane! SFL in the dark again. Noooooo

[toad strangler]

Yikes Gatorcane! SFL in the dark again. Noooooo

Verbatim that's not a strong system. No model has blown anything up in the long range at all.

[SFLcane]

Strongest run yet from the Caribbean. IF and that a big IF it’s even remotely close to this 988mb will leave you in the dark.

[LarryWx]

^Note that after this S FL hit from what easily could be a H, it runs up the SE US coast 10/8-9 as a still formidable TC. The most worrisome aspect of that would likely be the enhanced risk of major coastal flooding due to significant and long-fetched onshore winds being progged to start 9/30 and lasting at least through 10/8. The highest astronomic tides of October, which are near and just after the full moon, are during 10/6-9. If a strong TC were to then come along around 10/7-9, the coasts of FL/GA/SC would likely be at risk from another major coastal flooding event. Fortunately, this is still pretty far out in forecast time. But it obviously is something worth monitoring.

[toad strangler]

Strongest run yet from the Caribbean. IF and that a big IF it’s even remotely close to this 988mb will leave you in the dark.

Again, verbatim since we are talking about this just one run... that's a TS moving pretty quick. There could be a couple legit bands on the E side so outages would certainly be possible but not widespread.

[MetroMike]

Strongest run yet from the Caribbean. IF and that a big IF it’s even remotely close to this 988mb will leave you in the dark.

Again, verbatim since we are talking about this just one run... that's a TS moving pretty quick. There could be a couple legit bands on the E side so outages would certainly be possible but not widespread.

True Toad one run, but we have to see if this is the start of a trend as the conditions are ripe this year for such development to occur.
Remember the trend is your friend even in a negative connotation such as major TC.

[SFLcane]

Long range but surely a climo favored track for SFL plenty of octaine down there.

[LarryWx]

The 18Z GEFS is similar to the 12Z GEFS with many members becoming a TS+ and 8 (40%) becoming a H. Five of those Hs hit FL during 10/7-10. Two of those later hit GA/SC/NC 10/9-10 still as Hs. One hits TX/LA 10/13-14. Keep in mind that the members are run on low resolution. So, the # of Hs could easily be underdone.

[gatorcane]

The 18Z GFS consolidates the system a bit more quickly in the SW/Western Caribbean allowing it to develop more quickly. Let's see if this trend continues in future runs.

[johngaltfla]

The 18Z GFS consolidates the system a bit more quickly in the SW/Western Caribbean allowing it to develop more quickly. Let's see if this trend continues in future runs.

Let's not and skip to December 10th please.

What worries me is that the models have hard time with GoM intensity forecasts once a circulation develops near our coast as they tend to strengthen rapidly if shear relaxes.