2015 Global model runs discussion

[Alyono]

on the EC website (log in required), the ensembles are saying a 60-70% chance of some type of development. Most keep it weak as there is only a 10-20% chance of a tropical storm

[Steve]

Alyono,

If you don't mind me asking, from your experience with EC, how do those percentages usually work? Are there any typical trends that you would expect with percentage chance of an "x" forming as timing gets closer to possible genesis? Or in other words, if formation/Genesis was 3 days away vs 6 or 7 now, all things remaining equal, woukd that EC product reflect that with a higher percentage of likelihood that a system would develop into a TS or whatever? I'm curious from a historical perspective but more so in applying that to future prognostication. Thanks

18z GFS still moves energy and rainfall up toward the LA coast. It also shows a possible minor east coast system followed by what appears to be a messy but intensifying system heading for the Carolinas at the very end of the run. That's a lot of action to watch for even nothing pans out.

[Alyono]

Alyono,

If you don't mind me asking, from your experience with EC, how do those percentages usually work? Are there any typical trends that you would expect with percentage chance of an "x" forming as timing gets closer to possible genesis? Or in other words, if formation/Genesis was 3 days away vs 6 or 7 now, all things remaining equal, woukd that EC product reflect that with a higher percentage of likelihood that a system would develop into a TS or whatever? I'm curious from a historical perspective but more so in applying that to future prognostication. Thanks

18z GFS still moves energy and rainfall up toward the LA coast. It also shows a possible minor east coast system followed by what appears to be a messy but intensifying system heading for the Carolinas at the very end of the run. That's a lot of action to watch for even nothing pans out.

what I have seen is that the TS probabilities are often too low on systems that have yet to develop. That is why I tend to use the probability of any type of tropical cyclone

[Stormcenter]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
424 PM CDT TUE SEP 8 2015
.LONG TERM...

GFS AND EURO CONTINUE TO SHOW SOME FEATURE OVER THE BAY OF
CAMPECHE BY SUNDAY. EURO DEEPENS THE LOW OVER THE WEST GULF MONDAY
THROUGH THURSDAY OF NEXT WEEK WHILE GFS TAKES THE FEATURE TO THE
TEXAS COAST AND SOUTHEAST FLOW OVER THE WEST GULF NEXT. BOTH
INCREASE MOISTURE OVER TEXAS AND WEST LOUISIANA. WILL INCREASE
RAIN CHANCES OVER THE WEST ZONES FOR NEXT WEEK. THERE IS A GREAT
DEAL OF UNCERTAINTY WITH THE MODELS AND IT IS TO EARLY TO BUY OFF
ONE OR THE OTHER AT THIS TIME.

[stormlover2013]

18z just started rolling

[Alyono]

strong EPAC system looks to be causing shear. Not really any Gulf development

EPAC development appears very likely, which means I am discounting the ridiculous EC operational prediction. It appears to have some convective feedback as the ensemble control does not have that solution.

People need to stop thinking the EC is all that, when it is horrific at TC genesis and intensity forecasts

[stormlover2013]

18z is pretty bad also usually don't even look at that one

[Hammy]

I wouldn't completely write off the Euro's solution just yet, as it was the first system to pick up on Bill's development days before any other models did (and it was also discounted until 2-3 days before.)

[CYCLONE MIKE]

But in contrast it was the first one showing a system developing east of Florida and riding up the east coast as a pretty strong hurricane back in mid part the summer. Kept showing it run after run and low and behold nothing ever happened. Doesnt matter though ALL models have been bad to downright dismal this year regarding the tropics. Wxman put it best, will believe it when I see it.

[TropicalAnalystwx13]

The forecast setup certainly leaves the door open to development, with a slug of moisture being drawn north across the Bay of Campeche and into the Gulf of Mexico by an anomalously strong upper-level trough over the East U.S. There is no point in arguing the intensity of any potential system at this point until we see a disturbance take shape, if one indeed does.

[Ntxw]

But in contrast it was the first one showing a system developing east of Florida and riding up the east coast as a pretty strong hurricane back in mid part the summer. Kept showing it run after run and low and behold nothing ever happened. Doesnt matter though ALL models have been bad to downright dismal this year regarding the tropics. Wxman put it best, will believe it when I see it.

I think you're talking about 95L from late July, early August. In a sense it is kind of the same situation here, trough and front coming down into the gulf. Lower heights and pressures, the models like to spin up stuff. No doubt convection and disturbed weather will occur, will it spin up anything is up for debate and mostly modelling for now. Guidance loves to spin stuff up in these situations. If there is something real and consolidated coming up from the BOC then believable but if it's out of just disturbed weather it will be a slow messy process. With fronts nearby there will be shear.

[Hammy]

But in contrast it was the first one showing a system developing east of Florida and riding up the east coast as a pretty strong hurricane back in mid part the summer. Kept showing it run after run and low and behold nothing ever happened. Doesnt matter though ALL models have been bad to downright dismal this year regarding the tropics. Wxman put it best, will believe it when I see it.

All the models ended up being wrong on that one, and the Euro's intensity was extremely inconsistent and had intermittent runs where there was nothing developing at all. It was by no means consistent nor did it at any point show development within 120-144 hours (most runs started at 192 hours; I have the start point of the runs saved.) The models also tend to be extremely poor with frontal-based lows and seem to spin them up sometimes. And a strong hurricane was only shown on one run.

I'm not 100% buying development but I'd put it at least 50/50 if it continues to show it for another few runs.

[CYCLONE MIKE]

So true. And of course whatever may try and form out there will have tons of shear to deal with as well. I'm thinking it will be more like a fall hybrid system of course if it does develop.

[stormlover2013]

All models are hinting something

[KatDaddy]

Regardless of tropical develop in the WGOM there will be lots of moisture as well as more moisture in the EPAC with another tropical system possible behind Linda. Should the pattern allow both the EPAC and the GOM moisture to combine with a trough, the potential would be there for significant flooding. Just something to watch over the weekend.

[Dean4Storms]

The ECM appears to show energy coming together from the sagging tail end of the Cold Front this weekend that sweeps into the Western Gulf meeting the Tropical Wave that is just now reaching the Carib. moving westward. You get all that convergence into the Western Gulf I think the ECM solution is plausible, at least as far as a Low developing. The question will be what the upper levels are like for TC development, but I see a good potential.

[TheStormExpert]

For anything to even try and develop in the Western Gulf/Bay of Campeche wind shear is going to have to really come down soon. 50-60kts of shear definitely won't cut it, and it's increasing as well!

[NDG]

So I see that the 18z GFS does not come along with the crazy Euro's solution of its medium to long range forecast.
Let me remind you guys that the GFS for a long time did buy the Euro's solution of Erika becoming a strong hurricane close to FL.
The Euro has been way too bullish in the subtropics in its medium to long range forecast. IMO.

[stormlover2013]

Gfs 18z still had a disturbance just not strong

[gatorcane]

Will be interesting to see what the ECMWF does on the next few runs starting with tonight's run. No doubt I will be watching.

Penn state view of the 12Z run at 240 hours.

By the way the ECMWF shows yet another Cape Verde system. Development starts in about 4-5 days and it looks like a large system this time.