2018 Tropics: Global Model Runs Discussion (Out to day 16)

[Cpv17]

Is it just me or is the GFS run data seemingly taking a good deal longer to update??

It’s taking forever. The Euro will be done well before the GFS at this rate. Heck, by the time the 0z finishes, it’ll be time for the 12z 10 hours from now

[LarryWx]

Is it just me or is the GFS run data seemingly taking a good deal longer to update??

Rumor has it that the 0Z GFS gave up the ghost that it sort of had at 18Z.

[SoupBone]

So what's the reasoning behind that second wave heading more toward the Caribbean than the first wave? They are so close to each other, wouldn't they feel the same steering? It doesn't look like the second wave is all that much lower in latitude than the first. EDIT: After viewing it again, I guess it is the latitude that would keep it more West.

[stormlover2013]

So what's the reasoning behind that second wave heading more toward the Caribbean than the first wave? They are so close to each other, wouldn't they feel the same steering? It doesn't look like the second wave is all that much lower in latitude than the first. EDIT: After viewing it again, I guess it is the latitude that would keep it more West.

looks to be the ridge builds back in and could be carrib cruiser

[Sambucol]

So what's the reasoning behind that second wave heading more toward the Caribbean than the first wave? They are so close to each other, wouldn't they feel the same steering? It doesn't look like the second wave is all that much lower in latitude than the first. EDIT: After viewing it again, I guess it is the latitude that would keep it more West.

looks to be the ridge builds back in and could be carrib cruiser

Yes. It sure is low latitude. Read if a storm shoots the Yucatan Strait, it's usually a Texas/SW LA storm.

[chaser1]

Kudos to the overall global model suites for up to now not spinning up Tropical Zero-canes as some have done in the past. However, say what you want but i'm not too ready to buy into any solution that models are presently suggesting for multiple genesis quite yet. Firstly, I'm quite leery of the suddenly isolated and possible "flash in the pan" EURO development of the wave that's near Puerto Rico. I'm just finding it odd that the least likely model to pick up on a more micro-scale tropical system, happens to be the one potentially bringing a T.S. into Southeast Florida. Secondly, while nearly all models are thirsty to jump on the African Wave Train... climo would at least seem to corroborate some type of development there. That said, until we see where consolidation begins to take place I think it's way premature to begin to be all too sure whether a series of tropical missiles might take off to the Northwest or progress generally westward. A day or two timing along with a quickly forming T.D. verses a low pressure area that more typically slides off to the Southwest following it's progression off the African coast could mean a pretty big difference in ultimate track. Lastly, I'm a bit leery of the model's suggestion of a sudden large-scale breakdown of the Atlantic 500mb ridge. I'm not seeing any evidence of forecast dip in the progressive higher latitude 500mb flow over the E. CONUS or N. Atlantic. Even if there were a sharpening trough exiting the N.E. Atlantic, it's my thought that a slower to develop tropical system just emerging off the African coast might well remain caught in the lower level trades flow just far enough for ridging to build over the MDR as has been the case for nearly the entire season thus far. Best that I can see, there may be a developing TUTT well east of the E. CONUS in conjunction with a newly eastward building mid to upper level ridge over the U.S. coastline and W. Atlantic. Whether this feature that may develop well E. of the Bahamas plays much or any of roll toward the steering of eventual MDR systems yet to develop, is far from clear cut.

[ScottNAtlanta]

So what's the reasoning behind that second wave heading more toward the Caribbean than the first wave? They are so close to each other, wouldn't they feel the same steering? It doesn't look like the second wave is all that much lower in latitude than the first. EDIT: After viewing it again, I guess it is the latitude that would keep it more West.

Like I said earlier...In a pattern like this, you always have to watch for one to sneak under...these storms that recurve often leave a ridge in their wake that gets sandwiched between them and the next one. Also the following wave is slower to develop so it doesnt feel the weakness

[CourierPR]

Met. Joe Bastardi sees an ominous pattern evolving

@BigJoeBastardi
3h3 hours ago

The ridge over troubled water idea comes into play also Euro 6-10 with big positive DN over ne, for instance similar to pattern that gave us Andrew, Aug 22-26 1992

[Shell Mound]

[...] Lastly, I'm a bit leery of the model's suggestion of a sudden large-scale breakdown of the Atlantic 500mb ridge. I'm not seeing any evidence of forecast dip in the progressive higher latitude 500mb flow over the E. CONUS or N. Atlantic. Even if there were a sharpening trough exiting the N.E. Atlantic, it's my thought that a slower to develop tropical system just emerging off the African coast might well remain caught in the lower level trades flow just far enough for ridging to build over the MDR as has been the case for nearly the entire season thus far. Best that I can see, there may be a developing TUTT well east of the E. CONUS in conjunction with a newly eastward building mid to upper level ridge over the U.S. coastline and W. Atlantic. Whether this feature that may develop well E. of the Bahamas plays much or any of roll toward the steering of eventual MDR systems yet to develop, is far from clear cut.

I respectfully disagree. There is actually a robust signal on the 00Z EPS for 1) a gradual northward shift in above-average heights, 2) a retrogressive N-Hemisphere pattern, 3) and a shift in the Pacific pattern, preceding the emergence of a +PNA/-NAO regime. The long-wave evolution portends a gradual emergence of a +PNA (mean ridging) over the West Coast and a downstream trough digging over the Eastern Seaboard. This pattern starts to show up beyond day five on the EPS and becomes quite evident over time, especially by 8 September. At the same time, there are signs of a developing -NAO over the North Atlantic. Combined, the +PNA/-NAO trend would signify northwesterly flow over the western North Atlantic, and while the pattern would be quite conducive to reduced vertical wind shear and low MSLP over the MDR, it would also greatly reduce the risk of a TC threat to the U.S. mainland. Since we have been in a favourable steering pattern for landfalls for several weeks now (just lacking TC activity), and as patterns tend to shift over longer scales of time rather than a handful of days, the upcoming spike in TC activity (early to mid September) looks to coincide with a pattern shift toward a less-favourable large-scale steering regime for U.S. landfalls. This would likely last until late September, and by that time the Cabo Verde season (or at least U.S. threats from that area) begins to wind down climatologically, and then El Niño is likely to shut down the late-season Caribbean/GOM development in late September/October, owing to increasing vertical wind shear in those areas. That means the next two and half weeks are likely going to constitute our hurricane season, and the data presented here suggest that we only have another week before the U.S. threats shut down for 2018. Thus, this upcoming FL/Gulf threat would need to unexpectedly intensify much more than indicated and become a major hurricane to pose a significant U.S. threat, as the pipeline of threats is likely to shut down afterward, owing to the developing East-Coast trough.

[cycloneye]

12z Euro for days 7-10 has more prospects to develop. West runners?

[cycloneye]

@DrRickKnabb
When models start suggesting tropical cyclone development many days in advance in multiple parts of the Atlantic basin, while they might not be right about exactly when and where, it does indicate that the atmosphere is changing and it’s about to get busy overall for September.

 https://twitter.com/DrRickKnabb/status/1034789222899695616

[galaxy401]

That one storm moving off Africa in the long range Euro is moving directly west. That could be the one to watch.

[Cpv17]

That one storm moving off Africa in the long range Euro is moving directly west. That could be the one to watch.

The one in front of it we’ll have to watch as well.

[Hybridstorm_November2001]

Met. Joe Bastardi sees an ominous pattern evolving

@BigJoeBastardi
3h3 hours ago

The ridge over troubled water idea comes into play also Euro 6-10 with big positive DN over ne, for instance similar to pattern that gave us Andrew, Aug 22-26 1992

I hope he is wrong. Having lived through Andrew I would not wish such a scenario on my worst enemy. However, the abnormally strong and northward orientated Bermuda High has been bathing us in heat & humidity since late May in the East with few breaks. It has been a stubborn pattern which just hangs on and on.

[gatorcane]

FV3 GFS with two west runner MDR systems in the long-range:

[gatorcane]

The 18Z GFS has an interesting 850mb vortmax that develops north of Puerto Rico and beelines toward Florida and the Gulf in the long-range. Looks like a rare case of a ULL working down to the surface. Note “ridge over troubled waters” sending it west (210 hour frame shown on 500mb chart):

[Hurricaneman]

The 18Z GFS has an interesting 850mb vortmax that develops north of Puerto Rico and beelines toward Florida and the Gulf in the long-range. Looks like a rare case of a ULL working down to the surface. Note “ridge over troubled waters” sending it west (210 hour frame shown on 500mb chart):

Some notable hurricanes have formed that way like Bob 1991, and Joaquin 2015 so it wouldn’t be unprecedented

[Hurricaneman]

Also it seems the 12zEuro had a similar system in front of the current wave leaving Africa to the 18zGFS but looks like its been dropped by the 0zGFS but here’s where my curiosity peaks is what the Euro and GFS showing between the Caribbean wave and the wave coming off of Africa possibly the wave in the locked thread that hits the ULL and forms some kind of tropical system from that

[chaser1]

[...] Lastly, I'm a bit leery of the model's suggestion of a sudden large-scale breakdown of the Atlantic 500mb ridge. I'm not seeing any evidence of forecast dip in the progressive higher latitude 500mb flow over the E. CONUS or N. Atlantic. Even if there were a sharpening trough exiting the N.E. Atlantic, it's my thought that a slower to develop tropical system just emerging off the African coast might well remain caught in the lower level trades flow just far enough for ridging to build over the MDR as has been the case for nearly the entire season thus far. Best that I can see, there may be a developing TUTT well east of the E. CONUS in conjunction with a newly eastward building mid to upper level ridge over the U.S. coastline and W. Atlantic. Whether this feature that may develop well E. of the Bahamas plays much or any of roll toward the steering of eventual MDR systems yet to develop, is far from clear cut.

I respectfully disagree. There is actually a robust signal on the 00Z EPS for 1) a gradual northward shift in above-average heights, 2) a retrogressive N-Hemisphere pattern, 3) and a shift in the Pacific pattern, preceding the emergence of a +PNA/-NAO regime. The long-wave evolution portends a gradual emergence of a +PNA (mean ridging) over the West Coast and a downstream trough digging over the Eastern Seaboard. This pattern starts to show up beyond day five on the EPS and becomes quite evident over time, especially by 8 September. At the same time, there are signs of a developing -NAO over the North Atlantic. Combined, the +PNA/-NAO trend would signify northwesterly flow over the western North Atlantic, and while the pattern would be quite conducive to reduced vertical wind shear and low MSLP over the MDR, it would also greatly reduce the risk of a TC threat to the U.S. mainland. Since we have been in a favourable steering pattern for landfalls for several weeks now (just lacking TC activity), and as patterns tend to shift over longer scales of time rather than a handful of days, the upcoming spike in TC activity (early to mid September) looks to coincide with a pattern shift toward a less-favourable large-scale steering regime for U.S. landfalls. This would likely last until late September, and by that time the Cabo Verde season (or at least U.S. threats from that area) begins to wind down climatologically, and then El Niño is likely to shut down the late-season Caribbean/GOM development in late September/October, owing to increasing vertical wind shear in those areas. That means the next two and half weeks are likely going to constitute our hurricane season, and the data presented here suggest that we only have another week before the U.S. threats shut down for 2018. Thus, this upcoming FL/Gulf threat would need to unexpectedly intensify much more than indicated and become a major hurricane to pose a significant U.S. threat, as the pipeline of threats is likely to shut down afterward, owing to the developing East-Coast trough.

I can appreciate your perspective however see the teleconnections that you outline to potentially shut down threat to U.S. landfall at about September 8 to be premature. I think we agree on a northward progression of the overall Atlantic base ridge position. On the other hand August is nearly over and the Atlantic 500mb flow is commonly less strong and expansive as we move into September. One thing I've grown to appreciate over so many years and that is pattern persistance. Yes, patterns do change however I don't believe the net result you anticipate will signify a semi-permanent E. Conus trough to establish itself at 1200 hr's. on Sept. 9 LOL. While 500mb height falls may well begin to occur throughout the MDR during the days to come, I'm far less emboldened to believe that the same will occur over New England and possibly the mid U.S. seaboard for several weeks to come. Thus I respectfully disagree with your notion that significant landfall risk will be largely mitigated beyond the next 10 days or so. As for El Nino shutting down the Atlantic by late September? No, I believe not. Late October perhaps. That's not to say that I don't believe there may be a gradual increase in upper level shear but not to the extent that I believe the entire Caribbean, Gulf, and W. Atlantic will be fully shut down however.

[1900hurricane]

I suspect the system behind 90L depicted on the 00Z ECMWF moves more westwards than its predecessor largely because it isn't defined enough to feel the deeper steering currents. However, going more towards the medium range, the disturbance following that has a much more defined mid-level ridge over the top of it, likely moving in tandem with the system if the run is taken verbatim and extrapolated. This is a forecaster's eternity out with tons of time to change, but this is the one that has caught my eye wrt potential to track more westerly.