Potential System South of Cabo Verde Islands (Is Invest 91L)

[Hurricaneman]

But again has two competing vorts to start.

I can believe the GFS with the competing vortices but am a little on the side that the GFS is possibly giving convective feedback and overdeveloping this feature like it did with 99L

[Siker]

00z CMC pretty much identical to the GFS at 72 hours FWIW.

[Siker]

UKMET continues to show nothing.

[abajan]

GFS has been showing a hurricane passing uncomfortably close to the Leeward Islands next Saturday morning, for the last few runs now.

[RL3AO]

If the GFS is anywhere near correct, it will put the Atlantic above average single-handily for some time.

[USTropics]

But again has two competing vorts to start.

I can believe the GFS with the competing vortices but am a little on the side that the GFS is possibly giving convective feedback and overdeveloping this feature like it did with 99L

It's most likely overzealous on how fast this system will organize, but genesis isn't a result of convective feedback in this instance. The other models (including the earlier run of the ECMWF) are forecasting a strong vortex signature to exit the African coast and interact with the persistent monsoonal trough in the CATL that extends from 31N50W to 27N56W.

For those that aren't exactly sure what convective feedback is (since it gets thrown around here so often), here is a quick explanation:

Convective feedback usually occurs when the model develops a local bulls eye of convection and heavy QPF over a very short distance and time. The model then overcompensates, as the convective parameter causes a large amount of latent heat to be released into the atmosphere. This produces a maximum of vertical velocity around 500mb over the QPF bulls eye. This also usually results in the development of a local upper-level jet maximum and a small intense bulls eye of vorticity.

[Hurricaneman]

The last few runs of the GFS seem to be trending towards a stronger ridge with the trough retreating causing a thumb ridge but also trending south after 156 hrs which is not a trend I want to see as any real shifts could bring the US into the equation

[USTropics]

Always take these long range forecasts with a grain of doubt (especially this year), but the CMC and GFS model have a pretty significant storm through 240 hours.

00z GFS:


00z CMC:

[USTropics]

A significant number of GFS ensemble members are concentrated over or just north of the islands:

[AubreyStorm]

He we go!

[USTropics]

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Sun Aug 13 2017

1. A tropical wave that has just emerged off the west coast of Africa
is forecast to move westward over the next couple of days and merge
with a broad area of low pressure located southwest of the Cabo
Verde Islands. Thereafter, environmental conditions are expected to
be conducive for gradual development of the system while it moves
westward to west-northwestward at 10 to 15 mph over the open
tropical Atlantic Ocean.

* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...20 percent.

[Siker]

It looks like the Euro doesn't merge the two waves this run?

[USTropics]

The 00z ECMWF has delayed development, but shows a system just north of the Leeward Islands by 168 hours:

[AtlanticWind]

The 00z ECMWF has delayed development, but shows a system just north of the Leeward Islands by 168 hours:

A threat to the U.S and the islands on this euro run.

[USTropics]

One other environmental variable that we'll really have to watch is the forecasted strengthening of the Bermuda-Azores high. This will increase wind flow to the north, most likely accelerate movement speed of our AOI, and increase SAL spread (although there CURRENTLY appears to be a somewhat favorable absence of SAL between the CATL wave and the EATL wave).

[USTropics]

Currently the only model not showing development is the UKMET:

00z ECMWF at 240 hours:


00z GFS at 240 hours:


00z CMC at 240 hours:
[/quote]

[Siker]

Currently the only model not showing development is the UKMET:

If the UKMET is showing Euro like development we wouldn't actually see it on the text product because it's beyond 144 hours. Need to see graphics.

Edit: It has a further north, stronger version of the Euro.

[Kingarabian]

Would be pretty agitating if the models end up doing an about face.

[bamajammer4eva]

Would be pretty agitating if the models end up doing an about face.

No way that would happen HA HA

[AtlanticWind]

06Z GFS shows a tropical storm by Monday morning.