ATL: DORIAN - Post-Tropical - Discussion

[tolakram]

It's managed to moisten up the nearby environment.

COD midlevel WV loop
https://weather.cod.edu/satrad/?parms=global-halfdiskeastnorth-09-24-1-100-1&checked=map&colorbar=undefined

[Hypercane_Kyle]

I have seen with a lot of storms in the MDR will fire convection when they reach 55W. The warmer SST's make a big difference.

This is a good point. 55W really does seem to be the magic line for storms coasting in the MDR.

[NotSparta]

New convective burst:

[url]https://uploads.disquscdn.com/images/aea744597e982274ab72952d0868b2333a3115a73e53c7b5a82d66093d8c3aa3.gif[/rl]

Yeah its IR depiction is lacking. Let's see how it looks tomorrow.

Yeah, we'll see how the diurnal max is for it

[Chris_in_Tampa]

The sustained winds in the 5pm EDT advisory and the 8pm EDT NHC best track data were 35 knots, 40mph.

If you are looking at the 45 in those lines from model data, you're seeing 45 knot wind gusts and those were also 45 knots in the 5pm advisory.

[1900hurricane]

Needs to try and keep generating convection if it is to take advantage of its good structure.

[toad strangler]

Needs to try and keep generating convection if it is to take advantage of its good structure.

Meh, countless examples in the past of lame looking and weak systems go poof or go major in no time. In no way must this system do anything but struggle along to have a chance down the road.

[Emmett_Brown]

Needs to try and keep generating convection if it is to take advantage of its good structure.

Meh, countless examples in the past of lame looking and weak systems go poof or go major in no time. In no way must this system do anything but struggle along to have a chance down the road.

Both good points. Yeah, I remember Andrew pulsing and sputtering in dry air and shear. At one point it had pressure higher than many high pressure cells, and was still barely a TS.

[tolakram]

I believe it was Derek Ort's thesis that discussed how dry air is mainly an issue when shear is present. Shear is the main issue at the moment, if and when it lets up we'll see what happens.

[caneseddy]

End of forecast period has a 65 mph into Dominican Republic

[Kazmit]

End of forecast period has a 65 mph into Dominican Republic

That forecast point is inland. It would still likely be a hurricane upon landfall if this intensity forecast played out.

[Stormi]

End of forecast period has a 65 mph into Dominican Republic

That forecast point is inland. It would still likely be a hurricane upon landfall if this intensity forecast played out.

Agree.

[wxman57]

NHC is begging to reduce the predicted intensity. I'm sure they can see the predicted wind shear across the eastern Caribbean. Time for bed. Early day tomorrow.

[Stormi]

From what I've come to understand, being new to this, the better the convection & the tighter/better organized the rotation or spin - the better chance it will have at surviving the dry air as it can basically maintain itself regardless as we're looking at a big reduction in shear for the next few days. Obviously, only for so long - given. It also appears that a slightly N/NW track could possibly help it to avoid the worst of the dry air seen in model runs thus far. Or it could go straight to the grinder. Who knows?

[toad strangler]

NHC is begging to reduce the predicted intensity. I'm sure they can see the predicted wind shear across the eastern Caribbean. Time for bed. Early day tomorrow.

Well why would they be forecasting more aggressively than models if this was the case?

[eastcoastFL]

NHC is begging to reduce the predicted intensity. I'm sure they can see the predicted wind shear across the eastern Caribbean. Time for bed. Early day tomorrow.

Well why would they be forecasting more aggressively than models if this was the case?

The disco states that the intensity forecast has a very low confidence . They mention that it could be much weaker than expected due to its small size.

11pm disco

Confidence in the intensity forecast is particularly low due to a
number of factors. The small size of Dorian could make it
susceptible to large short-term swings in intensity (up or down).
While SHIPS diagnostics suggest that the wind shear will be below 10
kt for at least the next 72 h, UW-CIMSS shear diagnostics indicate
that the current shear is higher, more like 15-20 kt. And the
intensity guidance spread is also notably large, further decreasing
confidence in the forecast. For now, the NHC intensity forecast has
not been significantly changed, and shows Dorian near hurricane
strength when it approaches the Lesser Antilles in a few days. This
is a little above the intensity consensus and it should be stressed
that it is still too soon to pinpoint potential wind impacts across
those islands, given the large uncertainty in the forecast. The
official forecast then shows Dorian maintaining hurricane strength
across the northeast Caribbean, but it is certainly possible that it
could be weaker, especially given the expected surrounding dry
environment and a possible increase in wind shear forecast by the
GFS and ECMWF models. By the end of the forecast period, the NHC
intensity forecast is very close to HCCA and IVCN.

[toad strangler]

NHC is begging to reduce the predicted intensity. I'm sure they can see the predicted wind shear across the eastern Caribbean. Time for bed. Early day tomorrow.

Well why would they be forecasting more aggressively than models if this was the case?

The disco states that the intensity forecast has a very low confidence . They mention that it could be much weaker than expected due to its small size.

11pm disco

Confidence in the intensity forecast is particularly low due to a
number of factors. The small size of Dorian could make it
susceptible to large short-term swings in intensity (up or down).
While SHIPS diagnostics suggest that the wind shear will be below 10
kt for at least the next 72 h, UW-CIMSS shear diagnostics indicate
that the current shear is higher, more like 15-20 kt. And the
intensity guidance spread is also notably large, further decreasing
confidence in the forecast. For now, the NHC intensity forecast has
not been significantly changed, and shows Dorian near hurricane
strength when it approaches the Lesser Antilles in a few days. This
is a little above the intensity consensus and it should be stressed
that it is still too soon to pinpoint potential wind impacts across
those islands, given the large uncertainty in the forecast. The
official forecast then shows Dorian maintaining hurricane strength
across the northeast Caribbean, but it is certainly possible that it
could be weaker, especially given the expected surrounding dry
environment and a possible increase in wind shear forecast by the
GFS and ECMWF models. By the end of the forecast period, the NHC
intensity forecast is very close to HCCA and IVCN.

I support the NHC immensely. They do a tremendous job almost all the time. That write up is about as wishy washy as you will ever see them. Low confidence means high vigilance.

[Stormi]

So basically it's harder for models to get a better grasp on smaller storms not simply due to their size, but because of possible fluctuations of intensity that can occur much faster than with larger storms? That would make sense along with less shear needed to RIP up a smaller storm vs a larger one. This is why I ask

[AtlanticWind]

Have to be wishy washy at this point, Too many conflicting signals ATM.

[p1nheadlarry]

NHC is begging to reduce the predicted intensity. I'm sure they can see the predicted wind shear across the eastern Caribbean. Time for bed. Early day tomorrow.

Well why would they be forecasting more aggressively than models if this was the case?

The disco states that the intensity forecast has a very low confidence . They mention that it could be much weaker than expected due to its small size.

11pm disco

Confidence in the intensity forecast is particularly low due to a
number of factors. The small size of Dorian could make it
susceptible to large short-term swings in intensity (up or down).
While SHIPS diagnostics suggest that the wind shear will be below 10
kt for at least the next 72 h, UW-CIMSS shear diagnostics indicate
that the current shear is higher, more like 15-20 kt. And the
intensity guidance spread is also notably large, further decreasing
confidence in the forecast. For now, the NHC intensity forecast has
not been significantly changed, and shows Dorian near hurricane
strength when it approaches the Lesser Antilles in a few days. This
is a little above the intensity consensus and it should be stressed
that it is still too soon to pinpoint potential wind impacts across
those islands, given the large uncertainty in the forecast. The
official forecast then shows Dorian maintaining hurricane strength
across the northeast Caribbean, but it is certainly possible that it
could be weaker, especially given the expected surrounding dry
environment and a possible increase in wind shear forecast by the
GFS and ECMWF models. By the end of the forecast period, the NHC
intensity forecast is very close to HCCA and IVCN.

After the intensity forecasts with both Florence and Michael last year it feels to me like a wait-and-see. Once the synoptic scale picture is clearer then we'll have a better idea as to how strong Dorian is entering the ECarib. Not dismembering the NHC btw they're job ain't easy.

[AutoPenalti]

I’m still on the no development train.