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

[Kazmit]

If this system develops (which is looking increasingly likely) it will be a good indicator that the GFS is a reliable model for long range forecasting, especially after Alberto as well.

[LarryWx]

So, the 12Z Ukmet has a W Car TD at the end of its run but the 12Z GFS has the weakest TC of the last couple of days.

Meanwhile, out of 51 members, the 0Z Euro ensemble from last night had all of two members with a tropical low in the GOM late next week that gets down to 1004 mb or lower. Actually, they both get to 1000 mb or lower. But the key is that we're talking only 4% of the members with a low that got down to 1004 mb or lower late next week in the GOM.

[SoupBone]

I’ve asked this with Alberto but what up with all the dry air in the GoM? Is this just typical continental dry air?

Yeah, looks like it's being sucked up from under the 'death ridge' over Texas. I'm getting mirror images from Alberto here on these runs.

Outside of a stray shower, and a few days a few weeks ago with daily rain, the death ridge has been firmly in place for multiple weeks. It's hotter than a Texas BBQ on the 4th of July.

[Alyono]

GFS is also unrealistically fast with the motion. It has this moving about as fast as Nate last year

[tropicwatch]

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 144 HOURS
FORECAST POSITION AT T+144 : 13.8N 82.9W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 13.06.2018 144 13.8N 82.9W 1008 30

Do they only come out with this once a day or more?

[AdamFirst]

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 144 HOURS
FORECAST POSITION AT T+144 : 13.8N 82.9W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 13.06.2018 144 13.8N 82.9W 1008 30

Do they only come out with this once a day or more?

UKMET runs twice a day - 00z and 12z

[Siker]

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 144 HOURS
FORECAST POSITION AT T+144 : 13.8N 82.9W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 13.06.2018 144 13.8N 82.9W 1008 30

Can you post the link to this? I lost it after last season.

EDIT: Here’s a source that doesn’t have pressure and wind. Should update at exactly 11:20am/pm central.

https://www.metoffice.gov.uk/data/tropi ... wtnt80.txt

[LarryWx]

The 12Z CMC is much weaker than the prior run. This is partially due to it being weaker early on while in the W Caribbean, but also a lot of it is due to more land interaction later with a further west track. Let's see what the GEFS and GEPS show as well as the Euro/EPS.

[Aric Dunn]

Euro 72 hrs.. is it finally going to jump onboard ?

[LarryWx]

The 12Z GEFS is pretty similar to its prior run with some support for a E or C GOM TC late next week but not strong support with most lows fairly weak.

Meanwhile, the 12Z GEPS, like its prior run, has 3 members that get to 1003 mb or lower (actually all get down to 999 mb or lower) late next week in the GOM with all of them in the W GOM with one clearly a H. However, most members have still weak lows or nothing.

Next up: the all important Euro/EPS. From my perspective, there being a W Car/GOM TC mid to late next week is still iffy with no Euro support and barely anything from the EPS. But the 12Z Ukmet has a TD at hour 144 and the GFS/CMC suites show some support. Also, 6/11-20 has 26 TC W Car/GOM geneses on record, the most of the 10-11 day periods noted through August. So, it is something to monitor. I just wouldn't bet on it yet.

[chaser1]

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 144 HOURS
FORECAST POSITION AT T+144 : 13.8N 82.9W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 13.06.2018 144 13.8N 82.9W 1008 30

Do they only come out with this once a day or more?

Am I missing something? What model is this referencing?

[chaser1]

Looks like a UK TC alert format.... I think? Never mind...... went immediately to the end of the thread to first catch up on most current. Then, began to back-track and saw prior references to this being the UK model output

[Alyono]

How many times are we going allow ourselves to remain married to the EC?

Havn't we seen enough times that this is the type of genesis situation the EC really struggles with? It will spin up monsoon troughs that do not develop, but is often slow to spin up the ones that develop. I've been seeing this same thing play out in the BOB where it has been trying to develop a cyclone this week, when one is not forming

[Alyono]

This is the link to the UK

http://tgftp.nws.noaa.gov/data/raw/wt/wtnt82.egrr..txt

[chaser1]

168 hr.'s and still NADA from the EURO. Meanwhile, today's 12 GFS continues to push the genesis forward with a 1008 mb in the SW Caribbean in 120 hr's. Granted, its now showing a slightly weaker intensity and further east Fla. Panhandle landfall solution.... but this actually strikes me as more credible anyway. Regardless, it's kind of hard to discount the EURO not coming on board whatsoever in the 5-8 day time frame and if one wants to perhaps over-analyze it, one can make a slight argument that the EURO is tending to show an increase of 500mb vorticity in the BOC at 168 hr. The CMC, NAVGEM, and ICON have all backed off a deeper surface reflection while also beginning to suggest a more South/Central Gulf weakness instead; This coupled with the UK finally on board but also pointing toward a more West Gulf solution, leads me to believe that things are obviously still quite muddled. All the more impressive should the GFS solution verify of course. At only 120 hours out, i'm still leaning toward hanging my hat on pattern persistence and Climo.

[chaser1]

How many times are we going allow ourselves to remain married to the EC?

Havn't we seen enough times that this is the type of genesis situation the EC really struggles with? It will spin up monsoon troughs that do not develop, but is often slow to spin up the ones that develop. I've been seeing this same thing play out in the BOB where it has been trying to develop a cyclone this week, when one is not forming

So true. Oddly though, I seem to recall that the EURO has less issue with picking up on monsoon trough related genesis in the far E. Atlantic?? Why it loses a high resolution capacity to disseminate W. Caribbean/GOM development from these same broad gyre's, I just don't really understand. All I know is this; While the GFS has been quick to develop small spurious tropical systems in the past that may have not developed, it is seemingly far better at sniffing out smaller tropical cyclone development which if genesis occurred, would suggest a greater capacity of forecasting a narrow set of plausible dynamic conditions within an overall unfavorable region at that time. That would seem to make the GFS analogous to some hardened Las Vegas gambler. There's times when they hit it big, but others where they lose their shirt lol.

[LarryWx]

How many times are we going allow ourselves to remain married to the EC?

Havn't we seen enough times that this is the type of genesis situation the EC really struggles with? It will spin up monsoon troughs that do not develop, but is often slow to spin up the ones that develop. I've been seeing this same thing play out in the BOB where it has been trying to develop a cyclone this week, when one is not forming

Due to the different strengths and weaknesses of the various credible models, it is best to not be married to any one model or to any one run of the models. It is better to consider run to run trends of the overall credible model consensus, including ensembles, as a tool for guidance along with keeping long term climo in the back of one's mind as an additional tool. Also, it is important to keep one's possible biases (such as either anti-development or pro-development) from influencing them.

[Alyono]

How many times are we going allow ourselves to remain married to the EC?

Havn't we seen enough times that this is the type of genesis situation the EC really struggles with? It will spin up monsoon troughs that do not develop, but is often slow to spin up the ones that develop. I've been seeing this same thing play out in the BOB where it has been trying to develop a cyclone this week, when one is not forming

So true. Oddly though, I seem to recall that the EURO has less issue with picking up on monsoon trough related genesis in the far E. Atlantic?? Why it loses a high resolution capacity to disseminate W. Caribbean/GOM development from these same broad gyre's, I just don't really understand. All I know is this; While the GFS has been quick to develop small spurious tropical systems in the past that may have not developed, it is seemingly far better at sniffing out smaller tropical cyclone development which if genesis occurred, would suggest a greater capacity of forecasting a narrow set of plausible dynamic conditions within an overall unfavorable region at that time. That would seem to make the GFS analogous to some hardened Las Vegas gambler. There's times when they hit it big, but others where they lose their shirt lol.

It missed the recent Myanmar cyclone. Had nothing until the cyclone had formed. Same monsoon trough type of system

I think it hits the E Atlantic because those are often associated with strong waves interacting with the trough.

Something is off with the EC because there should at least be another EPAC TC, but it is not present either. It does not appear to be handling the trough properly

[LarryWx]

Euro 72 hrs.. is it finally going to jump onboard ?

The hour 90 12Z Euro map appeared as if it had more 850 vorticity than previous runs in the far S Car. and perhaps going in the direction of the GFS/CMC down there then. However, later 12Z Euro maps squashed this hint of increased vorticity and it amounted to essentially nothing and still another run with no TC. Let's see what the EPS members show.

[chaser1]

Bottom line, it appears that the EURO and the GFS keep pretty strong 500mb heights east of Florida. Where the two models seem to diverge is around the 120 hr. point. The EURO appears to build the pretty deep ridge from the surface up to 500 mb. westward with time. Meanwhile, the GFS does not build the surface reflection westward and continues to leave a portion of the monsoon trough to extend into the W. Caribbean and Central America. The GFS also indicates a stout 594 ridge E. of Florida that does not appear to migrate westward. It's large round orientation results in a deep south to north steering pattern from the W. Caribbean and into the Gulf which logically would want to steer any MLC poleward (assuming a somewhat vertically stacked system were in place).