2015 Global model runs discussion

[TheStormExpert]

Just by that satellite image you posted you can tell it already has a nice spin/vorticity to it.

It also starts development in 78-84hrs. and peaks @ 990mb before heading Northwest towards the Central Atlantic and Bermuda into the stable dry air.

[gatorcane]

:uarrow: Just by that satellite image you posted you can tell it already has a nice spin/vorticity to it..

It's a pretty impressive wave. In the loops below, you can see the spin it already has, now wonder the GFS is latching on to this one:

http://rammb.cira.colostate.edu/ramsdis ... display=24
http://rammb.cira.colostate.edu/ramsdis ... display=24

But so far the GFS is all alone with its prediction of a hurricane forming SW of the Cape Verde islands by days 4-5. We recall it was over bullish last year on these tropical waves and it may be the same issue this time. But the model has been upgraded since and so far has been doing a pretty good job across the Atlantic so far not being overly bullish

It also starts development in 78-84hrs. and peaks @ 990mb before heading Northwest towards the Central Atlantic and Bermuda into the stable dry air.

The GFS is also notorious for trying to recurve Cape Verde systems rolling off Africa into a weakness across the Central/East Atlantic too quickly. I wouldn't put too much stock into the model run beyond 5 days in this scenario.

[LarryWx]

I always like to consider climo of similar ENSO as one factor in trying to determine the likelihood of model predicted genesis in the MDR as well as the likelihood of anything from there later hitting the CONUS. For the 23 El Nino's that peaked as moderate to strong since 1877, have any storms on record that obtained TS strength east of 40W within the MDR actually reached the CONUS as a tropical cyclone? Believe it or not regarding the 14 storms in that category, the answer is yes though there was only one and it was way back in 1899:

2009's Ana, Bill, Fred: none did though Bill missed the NE US by only 200 miles still as a cat 1 H and the remnants of Fred somehow actually did make it to the SE US! (though it was no longer a TD)
2002's Dolly: no
1997: no TS's on record east of 40W in the MDR
1991's Danny: no
1987's Bret and Dennis: no
1986: no TS's on record east of 40W in the MDR
1982's Beryl: no
1972: no TS's on record east of 40W in the MDR
1965's Carol: no
1963: no TS's on record east of 40W in the MDR
1957's Carrie: no
1941, 1940, 1930, 1925, 1918, 1911, 1905: no TS's on record east of 40W in the MDR
1902's #3: no
1899's #3, #5, #7: #3 made it to the NC Outer Banks as a cat 3 before sharply recurving out to sea
1896, 1888, 1877: no TS's on record east of 40W in the MDR

Conclusion: 1) As is well known for stronger El Nino's, the threat to the CONUS from the eastern MDR is very low. However, 1899 shows that there is always the rare exception and 2009 shows that there was a relatively close call to the NE (Bill).

2) Based on the 8 moderate to strong El Nino seasons since the satellite era began (1966), an average of only exactly 1.0 storms became a TS east of 40W within the MDR vs. 1.7 storms for the other 41 seasons. Of those 8 seasons, 5 of them had at least one of those. So, it wouldn't be surprising if one did form there this season. Even the super Nino of 1982 had one (Beryl) though 1997 and 1972 had none. My educated guess is that either one or zero will become a TS east of 40W within the MDR but that none will hit the CONUS. If one does form there, it could obviously be the one that the 12Z GFS is showing.

[WPBWeather]

:uarrow: Just by that satellite image you posted you can tell it already has a nice spin/vorticity to it.

It also starts development in 78-84hrs. and peaks @ 990mb before heading Northwest towards the Central Atlantic and Bermuda into the stable dry air.

I think the central Atlantic is and has been dominated by a large high pressure system for some time now. Any weak or strong storms would steer around that, wouldn't they? And that is a danger this year as any storm that stays together gets steered our way.

[TheStormExpert]

:uarrow: Just by that satellite image you posted you can tell it already has a nice spin/vorticity to it.

It also starts development in 78-84hrs. and peaks @ 990mb before heading Northwest towards the Central Atlantic and Bermuda into the stable dry air.

I think the central Atlantic is and has been dominated by a large high pressure system for some time now. Any weak or strong storms would steer around that, wouldn't they? And that is a danger this year as any storm that stays together gets steered our way.

Actually there has been a persistent trough along the U.S. East Coast as of lately.

[Siker]

:uarrow: Just by that satellite image you posted you can tell it already has a nice spin/vorticity to it.

It also starts development in 78-84hrs. and peaks @ 990mb before heading Northwest towards the Central Atlantic and Bermuda into the stable dry air.

I think the central Atlantic is and has been dominated by a large high pressure system for some time now. Any weak or strong storms would steer around that, wouldn't they? And that is a danger this year as any storm that stays together gets steered our way.

Actually there has been a persistent trough along the U.S. East Coast as of lately.

This is true, but as you said it is a relatively recent development. There are signs in the ensembles / CFS that this will change to a more ridgey pattern as we get into August / September.

[AJC3]

I always like to consider climo of similar ENSO as one factor in trying to determine the likelihood of model predicted genesis in the MDR as well as the likelihood of anything from there later hitting the CONUS. For the 23 El Nino's that peaked as moderate to strong since 1877, have any storms on record that obtained TS strength east of 40W within the MDR actually reached the CONUS as a tropical cyclone? Believe it or not regarding the 14 storms in that category, the answer is yes though there was only one and it was way back in 1899:

2009's Ana, Bill, Fred: none did though Bill missed the NE US by only 200 miles still as a cat 1 H and the remnants of Fred somehow actually did make it to the SE US! (though it was no longer a TD)
2002's Dolly: no
1997: no TS's on record east of 40W in the MDR
1991's Danny: no
1987's Bret and Dennis: no
1986: no TS's on record east of 40W in the MDR
1982's Beryl: no
1972: no TS's on record east of 40W in the MDR
1965's Carol: no
1963: no TS's on record east of 40W in the MDR
1957's Carrie: no
1941, 1940, 1930, 1925, 1918, 1911, 1905: no TS's on record east of 40W in the MDR
1902's #3: no
1899's #3, #5, #7: #3 made it to the NC Outer Banks as a cat 3 before sharply recurving out to sea
1896, 1888, 1877: no TS's on record east of 40W in the MDR

Conclusion: 1) As is well known for stronger El Nino's, the threat to the CONUS from the eastern MDR is very low. However, 1899 shows that there is always the rare exception and 2009 shows that there was a relatively close call to the NE (Bill).

2) Based on the 8 moderate to strong El Nino seasons since the satellite era began (1966), an average of only exactly 1.0 storms became a TS east of 40W within the MDR vs. 1.7 storms for the other 41 seasons. Of those 8 seasons, 5 of them had at least one of those. So, it wouldn't be surprising if one did form there this season. Even the super Nino of 1982 had one (Beryl) though 1997 and 1972 had none. My educated guess is that either one or zero will become a TS east of 40W within the MDR but that none will hit the CONUS. If one does form there, it could obviously be the one that the 12Z GFS is showing.

I never fail to be impressed by some of the solid research that many of our members post, both amateur and professional. This is another example of some great info. Thanks for posting it!

[blp]

The 12z Euro is seeing the vorticity associated with the strong wave over Africa. The difference is that once it gets over the water after 72hrs it does not develop it like the GFS. The CMC is also showing it but keeps it a little longer than the Euro.

Euro


GFS

[Siker]

The greatest inhibitor this storm would encounter on the GFS's path is sub 26°C waters. Passing over those for a decent amount of time = weakening / opening up = losing any anticyclone aloft and succumbing to shear even after passing back into sufficiently warm waters.

[SouthDadeFish]

The greatest inhibitor this storm would encounter on the GFS's path is sub 26°C waters. Passing over those for a decent amount of time = weakening / opening up = losing any anticyclone aloft and succumbing to shear even after passing back into sufficiently warm waters.

Great point about the SSTs. Even if a TC does quickly develop by the Cape Verde islands, chances are it will quickly move into an environment that is unfavorable from a thermodynamic perspective. Cold SSTs and lots of dry air. This is what the 18Z GFS is showing.

[blp]

The greatest inhibitor this storm would encounter on the GFS's path is sub 26°C waters. Passing over those for a decent amount of time = weakening / opening up = losing any anticyclone aloft and succumbing to shear even after passing back into sufficiently warm waters.

Great point about the SSTs. Even if a TC does quickly develop by the Cape Verde islands, chances are it will quickly move into an environment that is unfavorable from a thermodynamic perspective. Cold SSTs and lots of dry air. This is what the 18Z GFS is showing.

That is a very good point their is a anomoly of -2C after 30W in its path.

[Hammy]

Euro is showing two strong waves, one being 1004mb, over west Africa at 240 hours, and GFS is showing development of the current wave in less than 72 hours now, so in three days we find out if the upgrades were worth anything.

[TheStormExpert]

06z GFS now ups the start of development of the TW to 60hrs. It peaks @ 983mb. on hr.156.

Also even though not likely, it shows a decent hurricane coming off of Africa strong and rapidly developing @ 384hrs!

[TheStormExpert]

Euro is showing two strong waves, one being 1004mb, over west Africa at 240 hours, and GFS is showing development of the current wave in less than 72 hours now, so in three days we find out if the upgrades were worth anything.

IMO it would be really bad and pathetic if the GFS failed this since it's now only 60-72hrs. out! Even I'm still very skeptical about this.

Would not blame the NHC if they refuse to lemon this area right away since the GFS has a bad history in the past season or so.

[Siker]

Euro is showing two strong waves, one being 1004mb, over west Africa at 240 hours, and GFS is showing development of the current wave in less than 72 hours now, so in three days we find out if the upgrades were worth anything.

IMO it would be really bad and pathetic if the GFS failed this since it's now only 60-72hrs. out! Even I'm still very skeptical about this.

Would not blame the NHC if they refuse to lemon this area right away since the GFS has a bad history in the past season or so.

Yeah, it's a little sad that a lot of people (including myself) wouldn't be surprised if nothing came of this system, despite it moving from the medium to short range over the course of 15 GFS runs, because of the GFS's history with this sort of thing.

[TheStormExpert]

Euro is showing two strong waves, one being 1004mb, over west Africa at 240 hours, and GFS is showing development of the current wave in less than 72 hours now, so in three days we find out if the upgrades were worth anything.

IMO it would be really bad and pathetic if the GFS failed this since it's now only 60-72hrs. out! Even I'm still very skeptical about this.

Would not blame the NHC if they refuse to lemon this area right away since the GFS has a bad history in the past season or so.

Yeah, it's a little sad that a lot of people (including myself) wouldn't be surprised if nothing came of this system, despite it moving from the medium to short range over the course of 15 GFS runs, because of the GFS's history with this sort of thing.

Not to mention I very well remember both last season and 2013 that it was spewing out Phantom Storms left and right kind of like it is doing now, so that should keep everyone including suspicious and weary that anything will ever materialize.

[gatorcane]

No mention by the NHC for possible development near the Cape Verde Islands? Development starts in the short-range on the GFS, 60 hours from now. I know the GFS had its problems last year but in the short-range like this, I don't recall it failing that bad, I recall it was in that dreaded 4-5 day range.

The ECMWF is notoriously not good at predicting genesis in the MDR so you really can't rely on it in this scenario. Of course the GFS is still all alone on development so I can see why the NHC is considering it an outlier right now.

[TheStormExpert]

Probably why the NHC isn't mentioning it in their TWO. In my opinion I think they will wait for an area of interest to appear just like they did with invest 94L.

Michael Ventrice
‏@MJVentrice
I wouldn't place bets on the GFS regarding possible Cape Verde system; Convection, diurnal cycle, AEW issues at play.
9:28 AM - 3 Aug 2015

[LarryWx]

I always like to consider climo of similar ENSO as one factor in trying to determine the likelihood of model predicted genesis in the MDR as well as the likelihood of anything from there later hitting the CONUS. For the 23 El Nino's that peaked as moderate to strong since 1877, have any storms on record that obtained TS strength east of 40W within the MDR actually reached the CONUS as a tropical cyclone? Believe it or not regarding the 14 storms in that category, the answer is yes though there was only one and it was way back in 1899:

2009's Ana, Bill, Fred: none did though Bill missed the NE US by only 200 miles still as a cat 1 H and the remnants of Fred somehow actually did make it to the SE US! (though it was no longer a TD)
2002's Dolly: no
1997: no TS's on record east of 40W in the MDR
1991's Danny: no
1987's Bret and Dennis: no
1986: no TS's on record east of 40W in the MDR
1982's Beryl: no
1972: no TS's on record east of 40W in the MDR
1965's Carol: no
1963: no TS's on record east of 40W in the MDR
1957's Carrie: no
1941, 1940, 1930, 1925, 1918, 1911, 1905: no TS's on record east of 40W in the MDR
1902's #3: no
1899's #3, #5, #7: #3 made it to the NC Outer Banks as a cat 3 before sharply recurving out to sea
1896, 1888, 1877: no TS's on record east of 40W in the MDR

Conclusion: 1) As is well known for stronger El Nino's, the threat to the CONUS from the eastern MDR is very low. However, 1899 shows that there is always the rare exception and 2009 shows that there was a relatively close call to the NE (Bill).

2) Based on the 8 moderate to strong El Nino seasons since the satellite era began (1966), an average of only exactly 1.0 storms became a TS east of 40W within the MDR vs. 1.7 storms for the other 41 seasons. Of those 8 seasons, 5 of them had at least one of those. So, it wouldn't be surprising if one did form there this season. Even the super Nino of 1982 had one (Beryl) though 1997 and 1972 had none. My educated guess is that either one or zero will become a TS east of 40W within the MDR but that none will hit the CONUS. If one does form there, it could obviously be the one that the 12Z GFS is showing.

I never fail to be impressed by some of the solid research that many of our members post, both amateur and professional. This is another example of some great info. Thanks for posting it!

AJC,
Thanks and you're welcome. I think that looking back at history/a group of analogs is quite a useful tool for forecasting though it is not a crystal ball. Exceptions to the rule occur, of course, and these are analogs, too. That's why I pointed out 1899 and the close call of Bill in 2009. If a CONUS hit like 1899 were to occur, that wouldn't mean this method actually fails, especially if 1899 is also noted in advance as an outside possibility as opposed to saying there's no chance for a CONUS hit. The method as I see it is a good way to get an idea of the probabilities of various scenarios.

[gatorcane]

The GFS is not backing down and insists on development of the wave about ready to roll of Africa pretty much as soon as it makes the splash and gets over water. The 12Z run shows a 1005MB low south of the Cape Verde islands in only 54 hours. Time frame is coming in each run. The difference between the GFS last year would be that by now it would have dropped the system as it had problems in the 4-5 day range developing systems.

If the GFS gets this right, combined with huge miss by the Euro on the SE US Coast system (where the Euro developed a full blown hurricane that didn't even come close to materializing), the GFS certainly may get some respect back. As Hammy mentioned, let's see if the big upgrade finally paid off for this model while the Euro upgrades may have caused some regressions with that model.

12Z GFS 126 hours, down to 983MB: