2017 Global Model Runs Discussion (Out to day 16)

[Alyono]

Hmmm...Now GFS in the epac lol. Well thankfully the 3 models that are showing development are

The GFS has been back and forth each run since last nights 18z run. Let’s see if the 12z run continues the trend, but having both of the best global models favoring the E-PAC on their latest runs tells you something.

tells you their el niño bias continues

This is ane xample of where we need METEOROLOGY not MODELOLOGY

[WeatherEmperor]

Hmmm...Now GFS in the epac lol. Well thankfully the 3 models that are showing development are

The GFS has been back and forth each run since last nights 18z run. Let’s see if the 12z run continues the trend, but having both of the best global models favoring the E-PAC on their latest runs tells you something.

tells you their el niño bias continues

This is ane xample of where we need METEOROLOGY not MODELOLOGY

So do you believe this will develop in the WC instead?


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[blp]

Hmmm...Now GFS in the epac lol. Well thankfully the 3 models that are showing development are

The GFS has been back and forth each run since last nights 18z run. Let’s see if the 12z run continues the trend, but having both of the best global models favoring the E-PAC on their latest runs tells you something.

tells you their el niño bias continues

This is ane xample of where we need METEOROLOGY not MODELOLOGY

Alyono, I don't understand on the GFS and Euro is how can the vorticity move into the EPAC with that strong trough sweeping through north of it. It would seem to me that anything down there would get pulled north. Complex situation I guess. The less reliable models seem more logical based on setup.

GFS


Euro

[Alyono]

The GFS has been back and forth each run since last nights 18z run. Let’s see if the 12z run continues the trend, but having both of the best global models favoring the E-PAC on their latest runs tells you something.

tells you their el niño bias continues

This is ane xample of where we need METEOROLOGY not MODELOLOGY

So do you believe this will develop in the WC instead?


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yep, just like Nate ended up developing on the Carib side

[gatorcane]

Add another less reliable model to CARIBBEAN-side development instead of EPAC. Looks quite strong too:

[Shell Mound]

Another key, in my view, is that global (dynamical) models often struggle to resolve just where convection concentrates along the ITCZ. This is far from the first case where continental and basin influences complicated forecasts, obscuring whether the eastern tropical Pacific or the Caribbean would win. The Pacific is a larger source of oceanic heat content than the southern Caribbean, but South and Central America also exert influence on convective patterns. Additionally, monsoonal gyrations are always difficult to resolve as far as placement of features and consolidation are concerned, though the ECMWF in particular is the most adept at resolving overall convective schema. After all, we are still in the long range; potential development, if any, is still a week or more away. Indicators have consistently highlighted 24 October as the earliest possible date for something to begin consolidating, whether in the eastern tropical Pacific or the southern Caribbean Sea. My climatology-based guess is that the Caribbean is most likely to feature development, given that the EPS and GEFS means, along with the weekly CFSv2, puts the monsoonal circulation over or just east of Central America. The overall position of the large-scale feature seems to tip the scale toward the Caribbean instead of the Pacific, though global models obviously struggle to determine where individual vorticity maxima may develop within the broad pattern, hence the confusion. The trend toward a negative NAO, positive PNA, and strong Scandinavian blocking in late October would tend to focus lifting mechanisms over the Caribbean, as low-level convergence would strengthen in that area, given a deepening trough over the East Coast and building subtropical ridging over the Caribbean. This pattern would also seem conducive to a general northward and northeasterly track of whatever forms over the Caribbean, i.e., toward the Antilles, Bahamas, and to eastward of Florida and the United States. Michelle (2001) is not a bad analog in terms of track, though at this stage intensity and location have yet to be pinpointed. But the prospects for development of some sort look good, with odds leaning toward the southern Caribbean.

One worrying sign: both the EPS and GEFS, including the operational runs, have suggested that conditions should be conducive to development. Note that the operational ECMWF has been quickly developing several lows over the southern Caribbean and eastern tropical Pacific; though the eastern-Pacific lows become dominant, the key is that they deepen fairly quickly. Within a matter of a few days it spins up several well-defined vorticity maxima. The weekly CFSv2 also indicates building upper-level anticyclonic flow over and just east of Central America, which is consistent with the influence of the MJO on and after 24 October. Thus, the signs are that whatever develops could find an ideal combination of high moisture (PWAT), low vertical wind shear, and still-high oceanic heat content, allowing it to consolidate and deepen steadily. This means that a late-season threat could well become serious, if it manages to develop. With La Niña and climatology in force, I think that the odds of a (strong) hurricane may begin to rise substantially over the next few days, as models begin to resolve the Caribbean as the likely focus of development.

[Blown Away]

12z GFS...

[blp]

Another key, in my view, is that global (dynamical) models often struggle to resolve just where convection concentrates along the ITCZ. This is far from the first case where continental and basin influences complicated forecasts, obscuring whether the eastern tropical Pacific or the Caribbean would win. The Pacific is a larger source of oceanic heat content than the southern Caribbean, but South and Central America also exert influence on convective patterns. Additionally, monsoonal gyrations are always difficult to resolve as far as placement of features and consolidation are concerned, though the ECMWF in particular is the most adept at resolving overall convective schema. After all, we are still in the long range; potential development, if any, is still a week or more away. Indicators have consistently highlighted 24 October as the earliest possible date for something to begin consolidating, whether in the eastern tropical Pacific or the southern Caribbean Sea. My climatology-based guess is that the Caribbean is most likely to feature development, given that the EPS and GEFS means, along with the weekly CFSv2, puts the monsoonal circulation over or just east of Central America. The overall position of the large-scale feature seems to tip the scale toward the Caribbean instead of the Pacific, though global models obviously struggle to determine where individual vorticity maxima may develop within the broad pattern, hence the confusion. The trend toward a negative NAO, positive PNA, and strong Scandinavian blocking in late October would tend to focus lifting mechanisms over the Caribbean, as low-level convergence would strengthen in that area, given a deepening trough over the East Coast and building subtropical ridging over the Caribbean. This pattern would also seem conducive to a general northward and northeasterly track of whatever forms over the Caribbean, i.e., toward the Antilles, Bahamas, and to eastward of Florida and the United States. Michelle (2001) is not a bad analog in terms of track, though at this stage intensity and location have yet to be pinpointed. But the prospects for development of some sort look good, with odds leaning toward the southern Caribbean.

One worrying sign: both the EPS and GEFS, including the operational runs, have suggested that conditions should be conducive to development. Note that the operational ECMWF has been quickly developing several lows over the southern Caribbean and eastern tropical Pacific; though the eastern-Pacific lows become dominant, the key is that they deepen fairly quickly. Within a matter of a few days it spins up several well-defined vorticity maxima. The weekly CFSv2 also indicates building upper-level anticyclonic flow over and just east of Central America, which is consistent with the influence of the MJO on and after 24 October. Thus, the signs are that whatever develops could find an ideal combination of high moisture (PWAT), low vertical wind shear, and still-high oceanic heat content, allowing it to consolidate and deepen steadily. This means that a late-season threat could well become serious, if it manages to develop. With La Niña and climatology in force, I think that the odds of a (strong) hurricane may begin to rise substantially over the next few days, as models begin to resolve the Caribbean as the likely focus of development.

I agree. Waiting on the Euro to make sense of this. I think the Euro will start honing in on the area of cyclogensis on the next couple of runs.

[WeatherEmperor]

12z Canadian FWIW




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[WeatherEmperor]

12z Navgem




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[caneman]

It would have to do it quickly. The Euro is,modeling a strong cold front for the Tampa Bay region next Thursday. How reliable is the Euro on cold fronts?

[LarryWx]

After looking at the 12Z models, I don't see any reason for FL to be overly concerned at this time. If we can get past 11/5 without any more hits, the odds would become very high based on history back 150 years+ that FL is safe for the rest of the season from the W Caribbean/GOM. Any threats to FL on the 12Z GEFS have now slipped to the 10/31-11/2 period, when there are 3 members out of 20 total hitting S FL with a TS+, with one a H. Other TCs stay S of FL. The key to me on this run is time slippage even though this run showed 3 hits vs 0 hits on the often quietest 6Z run. The 0Z had one FL hit on 10/29 and another on 10/30 before another hit 11/1 and another threat soon afterward. The 18Z GEFS of two days ago had one H hit W FL 10/28, another hit Keys/S FL 10/29, and a 3rd one hit Keys/SW FL 10/31 before then hitting the Panhandle 11/1. So, you can see the couple of days' time slippage of FL hits since the Mon 18Z GEFS.

[psyclone]

It would have to do it quickly. The Euro is,modeling a strong cold front for the Tampa Bay region next Thursday. How reliable is the Euro on cold fronts?

The front is coming and it will be of consequence. The overnight discussion out of Ruskin referenced it with expected passage on Tuesday:

"The weather pattern
changes by the middle of next week as an area of low
pressure and associated frontal boundary develops over the
northern gulf states and moves eastward. This will bring a
shift in the winds to the south by the beginning of next
week and then to the northwest by middle of next week. Rain
chances will be higher on Tuesday as the front passes, but
will quickly clear up by the middle of next week. This is
expected to be the biggest cool down since summer with
daytime highs only reaching the upper 70`s and possible low
80`s by the middle of next week."

[WeatherEmperor]

12z Euro is daring anybody to question its continued EPAC development




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[Shell Mound]

12z Euro is daring anybody to question its continued EPAC development

https://uploads.tapatalk-cdn.com/20171018/5e735b5a0af49c17eaa677199f9558cc.png

While not critiquing your point of view, I respectfully note that it develops multiple (!) eastern-Pacific systems. This actually reflects a pronounced model bias that has been evident in both of the major global models thus far this year. Another user pointed this out:

The GFS has had phantom storms form in the EPAC just west of C.A. [Central America] on its med[ium] to long range forecast for the past couple of months, it has been 80-90% wrong. Even the Euro has been forecasting phantom storms in in this area.

http://www.storm2k.org/phpbb2/viewtopic.php?p=2649700#p2649700

So I would suspect that the ECMWF is likely to be incorrect in its depiction of eastern-Pacific genesis. But I could be wrong. I am no meteorologist. (Note that it does show development in the Caribbean, based on the vorticity fields.)

[sunnyday]

Shell Mound,
Is this possible storm that you mentioned earlier this week that you feel may have 200 m p h winds?

[BYG Jacob]

So, the models are all agreeing on another gyre near the end of the month right?

[blp]

18z GFS developing the W. Carribean vorticity this time. Looks like it will be much stronger...

[WeatherEmperor]

18z GFS developing the W. Carribean vorticity this time. Looks like it will be much stronger...

Here is a closer look at that




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[LarryWx]

The 12Z EPS has only one of 50 members hitting FL with a TC (on 10/30) and overall pretty limited TC activity. As of now, I think the chance for a FL hit from a TC remains low at best for very late month, very early Nov.