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WxWatcher007

Major Hurricane Laura

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20 minutes ago, Baltimorewx said:

Seems like a decent little jog north on the last infared frame there

Laura is now within the threshold where we can expect wobbles here and there.

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1 minute ago, jpeters3 said:

I find it highly unlikely that the airplane's pressure sensor is that off.  If it is, they have bigger problems.  The aircraft are flying at different altitudes, and the most likely explanation is that the standard extrapolation formula is simply inaccurate in this particular hurricane.  There are known biases with these formulas.

I've been following hurricanes for years and I've never seen extrap off by that much if there wasn't a problem. It's usually off by a few mbs and reads a touch low. We have another plane in the storm right now at the same pressure altitude reading extrapolating pressure just fine. 

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Dancing CBs rotating around the center seems to be a trademark precursor of a major hurricane. We've watched these unfold numerous times over the years.

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1 minute ago, JasonOH said:

The NOAA plane is at 750mb and the Air Force is at 700mb. That may explain some of the differences.

Hmm. I thought they were flying at the same height. 

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1 minute ago, OSUmetstud said:

Hmm. I thought they were flying at the same height. 

Though, if you are right about the pressure sensor being off, then they might actually be at the same heights...

Makes sense that they would make passes at different altitudes though.  Don't want a mid-air collision in the middle of a hurricane...

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FWIW, the 06z HWRF has only slow strengthening tonight up until landfall. The rapid pressure drops seem to stop between 15-18z today.

Still takes it down to 937mb before landfall, peaking at around 120kts. That fits pretty well in line with expectations of a low end Cat 4 landfall.

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06z HMON with landfall near Holly Beach, or perhaps just East of there. Slightly deeper than the HWRF with peak minimum pressure of 932mb and 136kts. It's also a good six hours slower than the HWRF with landfall.

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2 minutes ago, jpeters3 said:

Though, if you are right about the pressure sensor being off, then they might actually be at the same heights...

Makes sense that they would make passes at different altitudes though.  Don't want a mid-air collision in the middle of a hurricane...

Lol. Yes. I'm just saying something is obviously off. Its not normal for the extrap to be that off. Maybe they're reducing from the wrong pressure level. Hurricane eyes are fairly well behaved thermodynamically. 

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3 minutes ago, NJwx85 said:

FWIW, the 06z HWRF has only slow strengthening tonight up until landfall. The rapid pressure drops seem to stop between 15-18z today.

Still takes it down to 937mb before landfall, peaking at around 120kts. That fits pretty well in line with expectations of a low end Cat 4 landfall.

I am thinking 120-135 mph at landfall.  I think that dry air to the west of the center keeps her somewhat in check.  

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Though, if you are right about the pressure sensor being off, then they might actually be at the same heights...
Makes sense that they would make passes at different altitudes though.  Don't want a mid-air collision in the middle of a hurricane...
The AF301 is 600 meters above the NOAA2, and guess what?


Has not transmitting in 30 minutes, we lost it again

Sent from my LML212VL using Tapatalk

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AF301 is back transmitting data, last report was 1219 utc!  Still a bit slow.  The strength of the winds that the plane is finding  in the southwest quadrant suggests Laura might be approaching 120 mph winds now.

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The difference between a 120 mph hurricane and a 160 mph hurricane is potentially catastrophic impacts and catastrophic impacts likely.  That wording is just all the more chilling, the advisory that Sunday evening as Katrina was beginning to make landfall when the NWS New Orleans stated that if caught outside certain death will occur.

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4 minutes ago, Kevin Reilly said:

I am thinking 120-135 mph at landfall.  I think that dry air to the west of the center keeps her somewhat in check.  

Again, just a trivial note....135mph will never be reported, due to aforementioned rounding....

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5 minutes ago, OSUmetstud said:

Lol. Yes. I'm just saying something is obviously off. Its not normal for the extrap to be that off. Maybe they're reducing from the wrong pressure level. Hurricane eyes are fairly well behaved thermodynamically. 

I actually have to back off my initial statement.  Back of the envelope calculation says that you need a 10 K difference in mean layer temperature to get pressure differences that large.  That can't be explained by the planes flying at different altitudes.  So something is wrong...

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The 30 nm eye is greatly concerning for such a large pressure drop. This is not a small system. Will take time for the vortex to ramp up due to the wide gradient. But that means fetch may be larger and a higher surge. Additionally Laura may intensify right into landfall without an ERC as there may simply not be enough time for outer banding to consolidate and organize with such a large initial eyeband. Even if it does, the eyeband likely makes landfall at a steady-state after having had 12 more hours to flirt with MPI.

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Just now, jpeters3 said:

I actually have to back off my initial statement.  Back of the envelope calculation says that you need a 10 K difference in mean layer temperature to get pressure differences that large.  That can't be explained by the planes flying at different altitudes.  So something is wrong...

Right. 

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21 hours ago, NJwx85 said:

On the GFS, the trough over the plains is strong enough to breakdown the ridge which allows Laura to take more of a Northerly turn in the Western Gulf and imposes some Southwesterly shear late in period.

MGH4okl.gif

The Euro has a much different trough evolution and thus the ridge to the North of Laura remains much stronger. Hence the further West track and lack of shear. I personally think the GFS is given far too much weight with tropical systems.

KsFgJ0l.gif

Looks like the Euro upper air pattern ended up being closer to correct. Not good news for those hoping for increasing shear.

500mb.gif?1598445943926

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13 minutes ago, jpeters3 said:

Though, if you are right about the pressure sensor being off, then they might actually be at the same heights...

Makes sense that they would make passes at different altitudes though.  Don't want a mid-air collision in the middle of a hurricane...

One got their last ATC altimeter surface pressure fix from Tampa, the other from NOLA lol.  Just kidding.

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Just now, NJwx85 said:

Looks like the Euro upper air pattern ended up being closer to correct. Not good news for those hoping for increasing shear.

500mb.gif?1598445943926

This whole discussion is fortified through latest satellite imagery as the cirrus outflow in the western and northwestern quadrants suggests an expanding upper level anticyclone with a divergent pattern strengthening and pushing westward, keeping the shear away from the circulation.  The CDO of Laura is expanding rapidly northwest and west with cirrus outflow developing and improving into the ideal category!

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3 minutes ago, USCAPEWEATHERAF said:

This whole discussion is fortified through latest satellite imagery as the cirrus outflow in the western and northwestern quadrants suggests an expanding upper level anticyclone with a divergent pattern strengthening and pushing westward, keeping the shear away from the circulation.  The CDO of Laura is expanding rapidly northwest and west with cirrus outflow developing and improving into the ideal category!

Yes, awful news. Will be interesting to see if this pushes the 12z guidance back further West.

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This is from the AF301...e1adb40107f8abc4e00e1316a3dfe474.jpg&key=10b4fe818ae47c5ab133bec3bf585b97f77c2abfe2ebe71ca70b4df87bad562b

Sent from my LML212VL using Tapatalk


This thing is off-the-chain...these are Wilma-esque drops in pressure.

Sent from my SM-G950U using Tapatalk

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the rate shes deepening at is concerning to say the least given the smaller size of her eye and the large size of the system itself. Is the shear shell encounter right before landfall even going to be able to have much actual impact on what shes capable of if shes a large, mid-high end cat 4 by that time?

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Tightly clustered now towards extreme Eastern Texas. Bad news as it would put Lake Charles in the Eastern eyewall. Good news is that it's far enough East that the winds are still blowing offshore at Galveston Bay.

niYim9g.png

Also, what's with all of those models keeping Laura at or near hurricane strength through day 5?

PFLxNyw.png

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