ATL: LAURA - Post-Tropical - Discussion

[Hypercane_Kyle]

Wow, recon is showing flight level winds of 72 knots.

[Nederlander]

I still say Marco appears to be weakening - This would have an effect on Laura, wouldn't it?

It's a good question. I think a few models have shown this, maybe the GFS?

Nearly all of the models forecasted weakening. The problem, particularly with the euro, is how weak it initialized Marco to begin with (weak TS vs hurricane). Therefore, Marco just kind of slowed down and begins drifting westward due to steering collapse. If it was that drastic of a swing, then it’s possible Marco could affect Laura down the road if it doesn’t exit the picture, but they are quite far apart as it stands now. I don’t see Marco playing a significant role in Laura’s track or intensity currently.

[supercane4867]

Intensity appears to be at least 55kt right now

[Hypercane_Kyle]

Flight level winds and SFMR suggest an intensity of at least 50 knots.

[aspen]

Based on the two recon passes, the NHC could bump up Laura’s intensity to 1000-1002 mbar and 50-55 kt for the 5pm advisory. She’s come out of Hispaniola in decent shape, and on this current track, she could miss much of the Cuban mountains and potentially come out into the Gulf somewhat stronger than anticipated.

[HurricaneEdouard]

GFDL and HWRF were the go-tos for intensity on intensity on this board back in 2005-2008, so I'm surprised HWRF's reputation has fallen behind its performance.

What I tend to see pros recommend (or what they should recommend, at any rate) is not relying on any one particular tool for forecasting, but rather pay attention to trends (both model trends with the storm itself since its formation, and climatological trends with storms of similar track so you can compensate for any systemic biases in the models e.g. the tendency for many models to underestimate ridges and overestimate troughs, thus the infamous rightward bias), the consensus aids, and how tightly the ensembles begin to consolidate or not (which reflects actual uncertainty in the forecast, unlike the essentially useless NHC "cone of uncertainty"); the HWRF is good for intensity, the EURO is good for track, but the most accurate forecasts for both track and intensity are the HCCA and TVCN/IVCN consensus tools and the FSU Superensemble (which is generally even slightly more accurate than the NHC official forecast for track and intensity, but all four are roughly comparable).

One reason why HWRF's reputation is so bad is because people don't use it correctly. So many like watching it blow up invests into major hurricanes, but that's not what the model should be used for. If you give HWRF recon data and a defined system, it can perform extremely well.

So it's essentially just for entertainment intensity-wise prior to recon data. I did notice it had more realistic forecasts with Gonzalo once the plane got out there.

I wouldn't say it's just for entertainment - it has been remarkably consistent with Laura's intensity forecast compared to the other models and if a major hurricane verifies in the Gulf, it would have been realistic from the very beginning regardless of recon data - but the way people incorrectly use it, as zhukm29 points out, probably is for entertainment. I used to be a regular back on the sadly now-dead FLHurricane forums and hypecasting, model wars and frenetic model-watching were always the problem compared to the actual long-term trends of the models themselves.

[Hammy]

Laura's pulling an Isaias except the shear that was in the latter's way afterwards doesn't seem like it is this time.

[Kingarabian]

Will the NHC actually go with 55-60kts after the reduction?

[ColdMiser123]

This is a 55 KT storm at minimum if you just go off of SFMR. 700 hPa FL wind also showed a peak of 72 KT, which supports 65 KT at the surface. Very interested to see how the NHC approaches the upcoming advisory on an intensity basis.

[Nederlander]

Will the NHC actually go with 55-60kts after the reduction?

55 kts seems justified

[Beef Stew]

Should make for a very interesting discussion come the 21z update...

[Hammy]

One reason why HWRF's reputation is so bad is because people don't use it correctly. So many like watching it blow up invests into major hurricanes, but that's not what the model should be used for. If you give HWRF recon data and a defined system, it can perform extremely well.

So it's essentially just for entertainment intensity-wise prior to recon data. I did notice it had more realistic forecasts with Gonzalo once the plane got out there.

I wouldn't say it's just for entertainment - it has been remarkably consistent with Laura's intensity forecast compared to the other models and if a major hurricane verifies in the Gulf, it would have been realistic from the get-go regardless of recon data - but the way people incorrectly use it, as zhukm29 points out, probably is for entertainment. I used to be a regular back on the sadly now-dead FLHurricane forums and hypecasting, model wars and frenetic model-watching were always the problem compared to the actual long-term trends of the models themselves.

I was there too (I believe as Rabbit) and migrated here once it started fading. Sad as that was my introduction to the online weather community.

Are the HWRF's intensity forecasts best disregarded for storms that are yet to have recon flights?

[Kingarabian]

Some Euro and GFS runs in the past 36-48 hours actually hinted that this may intensify after passing Hispaniola, going south of Cuba. This is probably what we're seeing. The weakening that's supposed to occur is when it supposedly moves WNW/NW close enough to entangle with Cuba again just before it emerges into the GOM.

[CrazyC83]

If this can develop an inner core and stay over water, I think Cuba and the Cayman Islands are in for a big surprise. I agree a hurricane watch is needed for them.

[HurricaneEdouard]

Edit: Accidental triple post.

[supercane4867]

Those winds could be enhanced by the frictional effect of Cuban mountains. I remember back in 2012 recon measured extremely high FL winds during Sandy's landfall in the same region as well.

[HurricaneEdouard]

This is a 55 KT storm at minimum if you just go off of SFMR. FL wind also showed a peak of 72 KT at a 700 hPa FL which supports 65 KT at the surface. Very interested to see how the NHC approaches the upcoming advisory on an intensity basis.

My best guess is they'll go with a straight down-the-middle compromise of 60 knots, but a repeat of the common "this suggests the top winds aren't mixing well down to the surface" line in discussions could easily yield a more conservative 55 knots.

[Kingarabian]

But I think it's pretty obvious that all solutions favoring a weak disorganized Laura are busting one by one.

[SouthernBreeze]

What would really throw a loop would be if Laura manages to skim the N coast of Cuba

[Kazmit]

The best it has looked its whole life.