ATL: TEN - Models

[jlauderdal]

Judging by the 18z guidance this looks to pass far enough north of Hispaniola/Mona/Winward passage to not be effected. Of course that all could change.

Per the models, think there's some other prohibitive factor that will not allow this to develop despite the area being a TC hotspot.

Do you happen to know what that other prohibitive factor might be?

shear

[Kingarabian]

Judging by the 18z guidance this looks to pass far enough north of Hispaniola/Mona/Winward passage to not be effected. Of course that all could change.

Per the models, think there's some other prohibitive factor that will not allow this to develop despite the area being a TC hotspot.

Do you happen to know what that other prohibitive factor might be?

NASA model has a moderately thick dust layer reaching the straits/Bahamas in 120-144 hours. Combine that with 20-25kts of shear and a very weak vort after it interacts with the TUTT and it would make sense for the system to remain weak.

[gatorcane]

Do you happen to know what that other prohibitive factor might be?

Looking at the GFS shear charts (0 to 120 hour animation below), the GFS seems to think an upper-level low will pinch off the NE part of the big TUTT currently in the Bahamas. Watch how the upper-low pivots south then SW and creates the hostile environment between hours 0 and 78. The GFS showed something similar with Gert but that forecast ended up being wrong. Note the upper-high in the Bahamas and Florida after 78 hours which would create favorable conditions:

[hd44]

It has been a very long time since we have had significant formation in storms in the vicinity of the Florida Key that people may forget about past quick forming storms there. That place used to be a hot spot.

[Bocadude85]

Per the models, think there's some other prohibitive factor that will not allow this to develop despite the area being a TC hotspot.

Do you happen to know what that other prohibitive factor might be?

NASA model has a moderately thick dust layer reaching the straits/Bahamas in 120-144 hours. Combine that with 20-25kts of shear and a very weak vort after it interacts with the TUTT and it would make sense for the system to remain weak.

If you believe the GFS shear forecast then yes 25kts is a lot of shear to over come, but at the same time SHIPS has shear below 10kts.

[AtlanticWind]

Per the models, think there's some other prohibitive factor that will not allow this to develop despite the area being a TC hotspot.

Do you happen to know what that other prohibitive factor might be?

NASA model has a moderately thick dust layer reaching the straits/Bahamas in 120-144 hours. Combine that with 20-25kts of shear and a very weak vort after it interacts with the TUTT and it would make sense for the system to remain weak.

Models just have not been very good that far out this year,so I would not count on these conditions being present 5 or 6
days out

[Kingarabian]

The models did not do an overly terrible job in their shear forecast for Gert. It was evident that Gert was under moderate shear for most of its lifetime, especially in its early days. Deep storms, hurricanes in particular, can create favorable shear environments for themselves. So that's what Gert did. It developed more than expected, and eventually it found pockets of favorable shear combined with very warm waters thus it was able to take off.

Same thing can happen with 92L if it holds on. But if it does not develop, don't be too surprised.

[Kingarabian]

Do you happen to know what that other prohibitive factor might be?

NASA model has a moderately thick dust layer reaching the straits/Bahamas in 120-144 hours. Combine that with 20-25kts of shear and a very weak vort after it interacts with the TUTT and it would make sense for the system to remain weak.

If you believe the GFS shear forecast then yes 25kts is a lot of shear to over come, but at the same time SHIPS has shear below 10kts.

SHIPS model has been especially bad this season. Wouldn't put any weight into it.

[AtlanticWind]

The models did not do an overly terrible job in their shear forecast for Gert. It was evident that Gert was under moderate shear for most of its lifetime, especially in its early days. Deep storms, hurricanes in particular, can create favorable shear environments for themselves. So that's what Gert did. It developed more than expected, and eventually it found pockets of favorable shear combined with very warm waters thus it was able to take off.

Same thing can happen with 92L if it holds on. But if it does not develop, don't be too surprised.

I agree, I've been at 50/50 chance on this one .we shall see

[Bocadude85]

NASA model has a moderately thick dust layer reaching the straits/Bahamas in 120-144 hours. Combine that with 20-25kts of shear and a very weak vort after it interacts with the TUTT and it would make sense for the system to remain weak.

If you believe the GFS shear forecast then yes 25kts is a lot of shear to over come, but at the same time SHIPS has shear below 10kts.

SHIPS model has been especially bad this season. Wouldn't put any weight into it.

SHIPS is always bad with extended range shear forecasts, my point was why believe the GFS over SHIPS when it has been just as bad? What has peaked my interest more then anything is the UKMET persistently developing 92L.

[Kingarabian]

If you believe the GFS shear forecast then yes 25kts is a lot of shear to over come, but at the same time SHIPS has shear below 10kts.

SHIPS model has been especially bad this season. Wouldn't put any weight into it.

SHIPS is always bad with extended range shear forecasts, my point was why believe the GFS over SHIPS when it has been just as bad? What has peaked my interest more then anything is the UKMET persistently developing 92L.

Because the SHIPS is based off the GFS yet it somehow has verified worse. Also not just its extended forecasts are bad but so are its short term. Latest example? The invest areas in the CPac. If we were going by the SHIPS forecast, those invest areas would've been a TC by now.

[RL3AO]

SHIPS is always bad with extended range shear forecasts, my point was why believe the GFS over SHIPS when it has been just as bad? What has peaked my interest more then anything is the UKMET persistently developing 92L.

The SHIPs shear forecast IS the GFS forecast. SHIPS is a statistical model. It needs a dynamical model to input atmospheric conditions so it can do the intensity calculations.

[CYCLONE MIKE]

Conditions favor rapid intensification somewhere near the Florida straights. Could see a major out of this one.

No, think you're getting a little carried away. Main models show next to nothing, and models we used to laugh at and make fun of show a minimal hurricane at best. Nothing comes close to suggesting a major coming out of this, if it even survives at all.

[SouthFLTropics]

Here we go with our 5:30PM Entertainment...GFS 18z Initialized

[SouthFLTropics]

Based on what we are seeing on satellite I have a hard time believing the initial vorticity for 92L is as poor as the GFS is showing it.

[Hurricaneman]

Based on what we are seeing on satellite I have a hard time believing the initial vorticity for 92L is as poor as the GFS is showing it.

It's because the GFS is poor at showing systems

[Hurricaneman]

If this system isn't initialized right like on the GFS then it's possible the whole run is trash

[Bocadude85]

SHIPS model has been especially bad this season. Wouldn't put any weight into it.

SHIPS is always bad with extended range shear forecasts, my point was why believe the GFS over SHIPS when it has been just as bad? What has peaked my interest more then anything is the UKMET persistently developing 92L.

Because the SHIPS is based off the GFS yet it somehow has verified worse. Also not just its extended forecasts are bad but so are its short term. Latest example? The invest areas in the CPac. If we were going by the SHIPS forecast, those invest areas would've been a TC by now.

Then why is the NHC using SHIPS and LGEM for intensity and disregarding the GFS and EURO for Harvey?

[Blown Away]

18z GFS... 54 hrs a little better defined and SW compared to 12z...

[Kingarabian]

SHIPS is always bad with extended range shear forecasts, my point was why believe the GFS over SHIPS when it has been just as bad? What has peaked my interest more then anything is the UKMET persistently developing 92L.

Because the SHIPS is based off the GFS yet it somehow has verified worse. Also not just its extended forecasts are bad but so are its short term. Latest example? The invest areas in the CPac. If we were going by the SHIPS forecast, those invest areas would've been a TC by now.

Then why is the NHC using SHIPS and LGEM for intensity and disregarding the GFS and EURO for Harvey?

The NHC always likes to blend things in and they like to go with models that match the current trends.