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Tropical Global Model Runs Discussion 2017

GaWx said:
The 18Z GEFS does it again with many hits on FL and the NE Gulf 10/3-8. Of course this could be a false signal but even the 12Z EPS has some hint of it.
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What in the wide, wide world of sports is a going on here? Today's 18Z GEFS is the 3rd 18Z GEFS in a row showing numerous members with western Caribbean TC genesis in the first week of October!! No other GEFS run in between these 3 runs has had much of anything! That is really, really strange. Come to think of it, I think there have been similar instances of sudden heavy signals of TC activity in the western part of the basin that were limited to some past 18Z GEFS runs earlier this season. What gives about the Happy Hour GEFS? Isn't there a Tshirt that says "We toss" in regard to the 18Z GFS? Deltadog used to talk about a drunk
model a lot though that may have been the "drunk doc". Maybe the problem is that the 18Z GEFS is drunk?

In all seriousness, is it possible that there is some kind of programming glitch in the 18Z GEFS? Is that possible? I'm going to try to start following and possibly even posting more regularly about future 18Z GEFS runs as regards the tropics to see if there really does appear to be a problem.
 
GaWx said:
In all seriousness, is it possible that there is some kind of programming glitch in the 18Z GEFS? Is that possible? I'm going to try to start following and possibly even posting more regularly about future 18Z GEFS runs as regards the tropics to see if there really does appear to be a problem.
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Maybe we need to all keep track of every run and document this. Perhaps this can even become a short term study to see which run is most accurate based off of time of day, since we all know the 18Z GFS is cursed or something lol.
 
From a pro met at Storm2K in response to me about my concern about the 18Z GEFS, there apparently really is something to the 18Z GEFS (and GFS) being overly biased toward TC genesis in the western basin:

"I've heard that there might be an actual bias in the 18z run relating to how the model is initializing during near-peak solar radiation in this part of the world. I can't remember the exact details or if it's been shown to occur in other parts of the world during other model runs.

Whatever is causing it, there has seemed to be a bias in over-forecasting TCs in the long range of the 18z GFS/GEFS. The programming doesn't change, but how the model initializes millions of data points each run is critical. If there is even a small bias in how the GFS starts the 18z run, it could grow into large errors over time."

Fascinating stuff!
 
I just went back to Tropical Tidbits and see that they still have GEFS runs going back to 18Z of 9/16. If one first chooses the 384 hour map for the 9/16 GEFS run (which is the map for 18Z of 10/2) and then repeatedly clicked on "next run", one can clearly see a strong tendency for the 18Z GEFS mean having lower pressures in/near the W Caribbean as of 18Z on 10/2 pretty much every run as compared to the nearby 0Z, 6Z, and 12Z runs! I'll never think of the 18Z GFS suite the same way again when it is on its own with a strong TC genesis signal in the western basin...well until if/when this bias toward too much TC activity apparently due to 18Z being the time near peak solar insolation is fixed.

Dang, I thought the "We toss" of the 18Z GFS was just being silly. Now I know why as there's science behind it!
 
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Taking the above further, would the 6Z tend to underdo TC genesis chances due to
it being in the middle of the night/zero solar insolation? Also, would the 12Z runs tend to show less activity than the 0Z runs due to it being a cooler time of day than 0Z in the western basin even though solar insolation is similar? Finally, do other models show these same biases?
 
GaWx said:
I just went back to Tropical Tidbits and see that they still have GEFS runs going back to 18Z of 9/16. If one first chooses the 384 hour map for the 9/16 GEFS run (which is the map for 18Z of 10/2) and then repeatedly clicked on "next run", one can clearly see a strong tendency for the 18Z GEFS mean having lower pressures in/near the W Caribbean as of 18Z on 10/2 pretty much every run as compared to the nearby 0Z, 6Z, and 12Z runs! I'll never think of the 18Z GFS suite the same way again when it is on its own with a strong TC genesis signal in the western basin...well until if/when this bias toward too much TC activity apparently due to 18Z being the time near peak solar insolation is fixed.

Dang, I thought the "We toss" of the 18Z GFS was just being silly. Now I know why as there's science behind it!
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Larry - the 18 Z is like eating left-over breakfast and lunch all over again, then immediately eating supper on top, and wondering afterwards why the system is upset ...
or so it seems IMHO ... o_O
Phil
 
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Like clockwork, the 0Z GEFS has much weaker (though not none) W Caribbean TC action in the means vs the 18Z GEFS. This was almost 100% predictable based on what we learned this evening about the 18Z. For the same reason, I predict that the next very active GEFS will be the next 18Z. Let's see what it will show.
 
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The 6Z GEFS mean, also like clockwork, shows very few sub 1,000 mb TCs in/near the W Caribbean in early Oct. The quiet contrast to last evening's (and the last week or so of 18Z GEFS runs) is almost laughable. I'm still looking for another active 18Z GEFS run this evening as silly as that sounds. I wish there were a way this could be fixed.

Meanwhile, the 0Z EPS has about 30% of its members with sub-1,000 mb TCs form in/near the W Caribbean during early Oct., a respectable signal, an increase over the 20% of yesterday's 12Z EPS, way more active than the 6Z GEFS run, and more active than the 0Z GEFS run on a % basis. However, it is nowhere near as active %wise as the 18Z GEFS run, of course.
 
The size comparison between Lee and Maria is crazy. There is the chance that later on today or tomorrow that Lee cold exceed Maria's winds too.
Lee_And_Maria_Sep242017morning.jpg
 
I just looked at the Tropical Tidbits GEFS runs again for 18Z on 10/2 and sure enough the 6Z GEFS was always the quietest run!! So, the 18Z GEFS was by far the most active, the 6Z was by far the least active, and the 0Z/12Z were in between every single day for the week's worth of runs available at the site.

So, my hypothesis is now that the 18Z GEFS is biased too active, the 6Z GEFS is biased too inactive, and the 0Z/12Z are closest to accurate/least biased.
 
The 12Z GEFS is much more active than the quiet biased 6Z GEFS and even a good bit more active than the 0Z GEFS in/near the western Caribbean in early Oct. The only recent runs more active are the last few 18Z GEFS runs (no surprise there). So, I consider this a legitimately somewhat stronger signal for development. Looking forward to seeing the Happy Hour GEFS, which I fully expect to be very active due to high activity bias and even a good bit more active than this relatively active 12Z GEFS.
 
Fwiw, the 12Z Euro has a weak (1006 mb), broad low in the NW Caribbean about 150 miles south of west-central Cuba moving slowly northward. It appears to then be slowly strengthening amidst low shear.
This is just something to keep in the back of your mind for potential in early October.
 
GaWx said:
Fwiw, the 12Z Euro has a weak (1006 mb), broad low in the NW Caribbean about 150 miles south of west-central Cuba moving slowly northward. It appears to then be slowly strengthening amidst low shear.
This is just something to keep in the back of your mind for potential in early October.
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Dadgum it Larry ... too much on the table already ... :confused:
 
GaWx said:
Fwiw, the 12Z Euro has a weak (1006 mb), broad low in the NW Caribbean about 150 miles south of west-central Cuba moving slowly northward. It appears to then be slowly strengthening amidst low shear.
This is just something to keep in the back of your mind for potential in early October.
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pcbjr said:
Dadgum it Larry ... too much on the table already ... :confused:
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That area is notorious for pressure bombs and its been virtually untouched this season :eek:
 
Looking at the 11-15 day 12Z EPS in/near the W Caribbean/Gulf/just off the SE US coast, it is somewhat more active than the already fairly active 0Z EPS for the 50 members as a whole with 10 (20%) potential Hs or sub 990 mb vs 9 (18%) on the 0Z EPS; and about 22/44% potential TS+ (sub 1000 mb) vs ~15 (30%) on the 0Z EPS and ~10 (20%) on yesterday's 12Z EPS.

Regarding the 10 apparent Hs, 1 hits N MX, 1 hits TX/LA line, and 2 hit E LA/MS. Regarding the other 6 as of day 15: 1 is about to hit LA, 3 are about to hit W FL, 1 is still well out in the W GOM moving slowly N, and 1 is moving NE well out in the open Atlantic.

Next up: the often over-dramatic 18Z GEFS (and 18Z GFS). I expect to see strong activity on this considering the rather significant signal on the 12Z GEFS, the pretty strong signal on the 12Z EPS, and the 18Z GEFS bias toward activity.
 
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GaWx said:
Looking at the 11-15 day 12Z EPS in/near the W Caribbean/Gulf/just off the SE US coast, it is somewhat more active than the already fairly active 0Z EPS for the 50 members as a whole with 10 (20%) potential Hs or sub 990 mb vs 9 (18%) on the 0Z EPS; and about 22/44% potential TS+ (sub 1000 mb) vs ~15 (30%) on the 0Z EPS and ~10 (20%) on yesterday's 12Z EPS.

Regarding the 10 apparent Hs, 1 hits N MX, 1 hits TX/LA line, and 2 hit E LA/MS. Regarding the other 6 as of day 15: 1 is about to hit LA, 3 are about to hit W FL, 1 is still well out in the W GOM moving slowly N, and 1 is moving NE well out in the open Atlantic.

Next up: the often over-dramatic 18Z GEFS (and 18Z GFS). I expect to see strong activity on this considering the rather significant signal on the 12Z GEFS, the pretty strong signal on the 12Z EPS, and the 18Z GEFS bias toward activity.
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Thanks for the info! Meanwhile, here comes the 18Z GEFS and it continues to hold the streak as it seems.
 
ForsythSnow said:
Thanks for the info! Meanwhile, here comes the 18Z GEFS and it continues to hold the streak as it seems.
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Yes, indeed, the 18Z GEFS streak of being by far the most tropically active of the GEFS runs in the western basin in early Oct. continues. The predictability of it is kind of funny. Practically every member becomes a TS+ and 50%+ become a H with several monster Hs. Contrast to the typical quietest GEFS, the 6Z, which had only one H and a few TSs.

So, there will practically definitely be a big downtick from this 18Z GEFS on tonight's 0Z GEFS and likely a further downtick on the 6Z GEFS. But don't let that fool you into thinking these downticks would mean much of anything.
 
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I'm going to restate what I have been saying about western ATL basin TC genesis/development GEFS biases in case some are not following what I'm saying:

- the 18Z GEFS has day after day been the most active GEFS run BY FAR. A theory has been presented at Storm 2K that this is due to 18Z being the time of max solar insolation in/near the western ATL basin.
- the 6Z GEFS has day after day been the least active GEFS run BY FAR.
- the 0Z/12Z GEFS have been in between the surrounding 18Z/6Z GEFS every time.

With a repeating pattern like this, there are obvious biases that need to be considered when looking at each GEFS run as randomness definitely doesn't explain this. When I see the 18Z GEFS, I assume it is too active. When I see the 6Z GEFS, I assume it is too quiet. The 0Z/12Z GEFS seem to be the most reasonable to me of the 4 runs since they're in between.
 
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