ATL: LAURA - Post-Tropical - Discussion

[superfly]

Last vortex shows 998 mb, so slightly weaker than before. Still re-organizing after land interaction.

[eastcoastFL]

All clear and An anti cyclone over the gulf. One little pocket of 50kt shear by the coast but overall clear sailing

[eastcoastFL]

Last vortex shows 998 mb, so slightly weaker than before. Still re-organizing after land interaction.

I didn’t see one lower than that. What was it before?

[HurricaneEdouard]

The issue with these graphics is that they go by the models wind estimates instead of central pressures. Nearly all the models are coming in with pressures that would support greater than 95kts.

Indeed, and that's despite some models (e.g. EURO) having lower resolutions (thus higher pressures than what it's "actually" forecasting, in a sense). In light of the pressures forecasted and the general model trends over the last 48 hours, NHC's intensity forecast seems conservative.

The euro is actually one of the higher resolution globals @ 9km. UKM is 10km, GFS is 13km, CMC is 25km.

High resolution for a global, yes; still too low of a resolution to accurately capture pressures of major hurricanes.

[superfly]

Last vortex shows 998 mb, so slightly weaker than before. Still re-organizing after land interaction.

I didn’t see one lower than that. What was it before?

NHC 11 pm advisory was 996 mb.

[eastcoastFL]

Last vortex shows 998 mb, so slightly weaker than before. Still re-organizing after land interaction.

I didn’t see one lower than that. What was it before?

NHC 11 pm advisory was 996 mb.

I don’t think there’s been any recon passes at 996. Maybe they adjusted it to 996 for some reason. I don’t quite understand how all of that works.

[Highteeld]

I didn’t see one lower than that. What was it before?

NHC 11 pm advisory was 996 mb.

I don’t think there’s been any recon passes at 996. Maybe they adjusted it to 996 for some reason. I don’t quite understand how all of that works.

They're estimating based off surface obs, wind-adjusted dropsondes, and extrapolated pressure

[eastcoastFL]

NHC 11 pm advisory was 996 mb.

I don’t think there’s been any recon passes at 996. Maybe they adjusted it to 996 for some reason. I don’t quite understand how all of that works.

They're estimating based off surface obs, wind-adjusted dropsondes, and extrapolated pressure

That’s right. I never understood how they do the extrapolating

[Sanibel]

That last hit on Cuba took a toll...

Not according to recon.

Or according to the NHC Discussion:

Since then the storm has moved across western Cuba and is now
coming off the island and over the extreme southeastern Gulf of
Mexico. Radar data from Cuba and satellite images indicate that
the storm has become better organized with deep convection
beginning to wrap around the center with persistent thunderstorms
on the south side. Data from the NOAA and Air Force Hurricane
Hunters indicate that the pressure has fallen to 996 mb and that
the winds are around 55 kt.

Hurricane Eduoard wrote: You've been saying this after every land interaction Laura has undergone, when it's actually strengthened each time. With so many new users browsing this thread looking for info, I think we should keep the blatant contradictions with the official NHC discussions and advisories down to a minimum.

I think they are talking about what it did today when it went over water south of Cuba...

The storm had the top convection rip away and displayed visibly poorer form upon crossing that last part of Cuba...It might be coincidence due to a change from Caribbean to Gulf or it might have been one last trip-up of a core that was just recovering from the last land crossing...

In no way am I saying the system is weakening or anything like that...I'm just saying appearance...

An opinion shared by this professional CBS meteorologist at 3:07 where he says "You can see, kind of struggling because of all the land interaction":

https://www.youtube.com/watch?v=FCQg9KPEgXc

[HurricaneEdouard]

I don’t think there’s been any recon passes at 996. Maybe they adjusted it to 996 for some reason. I don’t quite understand how all of that works.

They're estimating based off surface obs, wind-adjusted dropsondes, and extrapolated pressure

That’s right. I never understood how they do the extrapolating

So, with a dropsonde, if there's wind detected, it means it missed the exact centre; the rule of thumb is to subtract 1mb from the measurement for every 10 knots of wind to derive the true minimum central pressure. The pressures you see in the raw recon data (not the vortex data message, which tends to include the dropsonde measurement if there was one, but the raw recon data every 10 minutes) are not dropsonde measurements, but rather pressures extrapolated from flight level, and so are less accurate than dropsonde measurements.

[Highteeld]

Convection near the center seems to be improving once again.

[Hypercane_Kyle]

Center should be right next to that hot tower based on recon.

[Hurrilurker]

So it looks like the northern center won out.

[FLpanhandle91]

I think that newest hot tower will be the beginning of what will become Laura's CDO. Inflow is no longer blocked by Cuba.

[ConvergenceZone]

Because of such low shear, I wonder if this will ever get that chance to get that pinwheel appearance?

[Highteeld]

Pressure down about 1/2 mb from the last pass per extrapolation

[aperson]

Looks like it jogged SW some since the last fix

[Highteeld]

Looks like it jogged SW some since the last fix

https://media.discordapp.net/attachments/744994799861366868/747681336071815238/recon_AF309-1313A-LAURA_zoom.png

These jogs SW are not good for Houston. I'm starting to think that's the landfall location.

[eastcoastFL]

They're estimating based off surface obs, wind-adjusted dropsondes, and extrapolated pressure

That’s right. I never understood how they do the extrapolating

So, with a dropsonde, if there's wind detected, it means it missed the exact centre; the rule of thumb is to subtract 1mb from the measurement for every 10 knots of wind to derive the true minimum central pressure. The pressures you see in the raw recon data (not the vortex data message, which tends to include the dropsonde measurement if there was one, but the raw recon data every 10 minutes) are not dropsonde measurements, but rather pressures extrapolated from flight level, and so are less accurate than dropsonde measurements.

Thank you for explaining that. I’ve always wondered how that worked.

[Highteeld]

Hurricane force flight level winds measured