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

[Weather150]

If you look carefully, the development on the ECMWF is linked to a mesoscale convective vortex (MCV) currently over Missouri that moves east and ends up off the NC coast. The ECMWF and mesoscale models such as the NAM have trended much stronger on this MCV in the short-term.

https://i.imgur.com/fR4Exqr.gif

As others have noted, Arthur in 2014 also formed from a MCV that moved off the GA coast and took on tropical characteristics.

This feature?

[LarryWx]

12z Euro appears to have a TS off NC on Wednesday. Hard to discount the possibility of development when the Euro has shown it for consecutive runs.

Though surprising to me to still have something similar at 12Z, I’m still discounting it as it, as noted by siker, develops a closed surface low over land in S NC that then moves offshore and strengthens. If this were a frontal related meso-scale low over land in August or maybe even in July progged to move offshore and develop (similar to what happened in 1983 in the N Gulf) and it ALSO had support from the UKMET, the GFS, and the GEFS, I might give it a decent chance. But this is the present day Euro, which has its quirks with development over land or just offshore like it did over TX as well as barely offshore E FL recently. Furthermore, it has support only from the on again ICON and CMC. So, I’m sticking with this being a fake TC and still with high confidence for at least now knowing late June climo back to 1851 is mainly on my side.

[jconsor]

It is a rare but not unprecedented scenario for an early-season tropical cyclone to develop from a mesoscale convective system that originates over the US and drifts offshore. Another example is Hurricane Danny in 1997:

https://www.nhc.noaa.gov/data/tcr/AL051997_Danny.pdf

If you look carefully, the development on the ECMWF is linked to a mesoscale convective vortex (MCV) currently over Missouri that moves east and ends up off the NC coast. The ECMWF and mesoscale models such as the NAM have trended much stronger on this MCV in the short-term.




As others have noted, Arthur in 2014 also formed from a MCV that moved off the GA coast and took on tropical characteristics.

Thanks for that, was having trouble pinning down the root disturbance.

[LarryWx]

The 12Z EPS has more members (about 10 of 50) than the only a couple of the 0Z EPS with a low of 1004 mb or stronger off the E coast of the US with almost all of them moving NE paralleling the coast similar to the operational Euro. Though that’s interesting, I still don’t think there will be a TC coming out of this.

[Weather150]

12z EPS.

[LarryWx]

Fwiw, though the low is very weak, I think the 12z NAVGEM is the 1st NAVGEM run with anything off the US east coast. Meanwhile, the JMA appears to have very little or nothing from the NC mesocomplex.

[Weather150]

18z ICON much weaker.

[Alyono]

the 6 and 18Z ICON seem vastly different from the 0 and 12Z. I've noticed that with some other runs

I wonder if they do not give the same weighting to satellite and radar obs and are using basically the previous 6 hour forecast as the starting point

[Siker]

the 6 and 18Z ICON seem vastly different from the 0 and 12Z. I've noticed that with some other runs

I wonder if they do not give the same weighting to satellite and radar obs and are using basically the previous 6 hour forecast as the starting point

Maybe we only get out to 120 hours at 6z and 18z because it’s a lower quality starting point?

[LarryWx]

The Happy Hour (18Z) GFS has no tropical activity of note throughout its run. Even the 18Z GEFS' 21 members haven't even a single surface low stronger than 1004 mb through 10 days+ throughout the tropics and subtropics (south of 35N) of the Atlantic basin. I found only one low barely below 1004 mb for less than 2 days well east of the NC/Va border that originates from the NC mesocomplex and that never does much. I mean it almost couldn't look any quieter. What a contrast to the 12Z Euro and even to the 12Z EPS to some extent!

[Alyono]

as I suspected would happen, the 0Z ICON again cranks this up

[TheAustinMan]

Our model system of interest for the East Coast has made an appearance on the UKMET output. Appears to be an ESE track towards Bermuda, at least until t=144 hours. Source: http://tgftp.nws.noaa.gov/data/raw/wt/wtnt82.egrr..txt

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 114 HOURS
FORECAST POSITION AT T+114 : 34.8N 67.7W

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
0000UTC 30.06.2018 120 35.1N 67.8W 1009 28
1200UTC 30.06.2018 132 34.1N 67.2W 1009 32
0000UTC 01.07.2018 144 33.5N 65.6W 1009 32

[Alyono]

I think we can throw the GFS into the trash can

Just check out the current IR of the MCS over Missouri and Arkansas and compare that to the simulated IR of the GFS

Even at 0Z, it did not have the convection over Arkansas

[LarryWx]

The 0Z GEFS and GEPS are very quiet throughout the Atlantic basin tropics and subtropics through day 10+.

[Alyono]

The 0Z GEFS and GEPS are very quiet throughout the Atlantic basin tropics and subtropics through day 10+.

That's because it does not have the MCS

I could not care less what the GFS says when it misses a fairly large scale MCS

[Kingarabian]

Euro looks much weaker.

[Alyono]

Euro looks much weaker.

going towards an ET low

I'd give the tropical development chances at 25 percent now

[GCANE]

Impressive MCS blowing up over Oklahoma and Kansas.

60 to 70 mph winds reported.
50 to 60 knot low-level jet measured.

[GCANE]

No surface low for the MCS.
Looks like a negative-tilt trof at 700mb.
500mb has a low in a negative-tilt trof.
300mb has a low in a positive-tilt trof.

Tons of hail and wind reports.

[GCANE]

SREF degrades the 500mb trof by the time it hits the coast.