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WxWatcher007

Major Hurricane Laura

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15 minutes ago, vortex95 said:

This makes me wonder about the calibration of the SFMR.  There has been concern with the calibration since 2016, and this is an ongoing active area of study.  It seems to have a high bias for extreme winds.  I mean look at Dorian, 910 mb and 185 mph?  Ok, Gilbert 888/185 and Wilma 882/185, and Gilbert and Wilma had pinhole eyes.  Dorian had a large eye, like Laura does now.  Matthew 160 and only 941?  That's the highest wind for a the highest pressure for a Cat 5 in the Atlantic.  Charley's 150/941 a makes sense since it has a pinhole eye and was undergoing very strong RI at the time.

it's one of two things, either the SFMR winds are correct and thus we have to go back and adjust winds up for many historical intense hurricanes, or it high bias is real and recent intense Atlantic TC winds need to be adjusted down.  Operationally, Irma's winds were 185 mph, but in post-season analysis, they were lower to 180 mph presumably b/c of the high SFMR bias.

The Labor Day Hurricane in 1935 was 892 mb and assigned 185 mph in re-analysis, but I believe intensity is capped at 185 mph for pre-recon hurricanes in the Hurricane Re-analysis Project.  This hurricane was very small (smaller RMW than Andrew) and given what we know now about hurricane structure and dynamics, chances are good it had winds around 200 mph.  It gets quite tricky to determine the true strength of very intense TCs w/o actual in situ data.   And the smaller they are, the harder it is, even in this day and age with advanced satellites.  The Dvorak scale does not do well with small intense TCs overall.

I mean the dropsonde caught 128kts in that pass with Laura. I don't really know enough about SFMR calibration studies to comment but the discussion doesn't seem relevant to this storm based on the dropsonde and radar data we have.

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Just now, KoalaBeer said:

Yup. As bad and as horrifying as Laura will be, I couldn't shake the thought today that Laura could of been one of, if not the worst natural disaster in US history if it came ashore 100 miles or so west into the Houston metro. This is of course no condolence to the folks about to lose everything in SW Louisiana. 

You may not be wrong on that. We’ve never really had a situation like this directly hit that area besides over 100 years ago. Such a densely populated region from the beach inland N/NW. The fast speed and large wind field inland would also have maximized the damage in the suburbs. 

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000
WTNT63 KNHC 270054
TCUAT3

Hurricane Laura Tropical Cyclone Update
NWS National Hurricane Center Miami FL       AL132020
800 PM CDT Wed Aug 26 2020

...800 PM CDT POSITION UPDATE...
...POSSIBLE TORNADOES OCCURRING IN LAURA'S OUTER BANDS OVER 
SOUTHEASTERN LOUISIANA AND EXTREME SOUTHWESTERN MISSISSIPPI...

SUMMARY OF 800 PM CDT...0100 UTC...INFORMATION
----------------------------------------------
LOCATION...28.7N 93.1W
ABOUT 95 MI...155 KM S OF LAKE CHARLES LOUISIANA
ABOUT 95 MI...155 KM SSE OF PORT ARTHUR TEXAS
MAXIMUM SUSTAINED WINDS...150 MPH...240 KM/H
PRESENT MOVEMENT...NNW OR 335 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...937 MB...27.67 INCHES

$$
Forecaster Berg/Pasch

 

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Not trying to rain on people's parade,  But can we take some of the historical stuff to a different thread? Thanks in advance. 

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Just now, LakeEffectKing said:

Not trying to rain on people's parade,  But can we take some of the historical stuff to a different thread? Thanks in a trance.

Make it so.

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2 minutes ago, Windspeed said:

Thanks to Onderlinde (Weathernerds), here's another classic NHC AVN animation...

amazing how consistent the lightning production has been around the eyewall.

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Mesoscale Discussion 1586
   NWS Storm Prediction Center Norman OK
   0747 PM CDT Wed Aug 26 2020

   Areas affected...much of Louisiana...far eastern Texas and southwest
   Mississippi

   Concerning...Tornado Watch 452...

   Valid 270047Z - 270245Z

   The severe weather threat for Tornado Watch 452 continues.

   SUMMARY...Shear will continue to increase with the approach of
   Hurricane Laura, with sporadic tornadoes possible within developing
   bands of storms through tonight. The greatest tornado risk will
   exist within the northeastern quadrant of the storm, primarily over
   Louisiana. As such, a new tornado watch will be needed.

   DISCUSSION...Objective analysis shows gradually increasing low-level
   shear over the area, with 0-1 SRH of 300-400 m2/s2 across southwest
   Louisiana early this evening. Shear will increase overnight as
   Hurricane Laura continues northward toward coastal Louisiana and
   Texas. Low-level moisture quality will also increase near and east
   of the center track, with dewpoints at or above 77 F. This should
   result in favorable SBCAPE for supercells embedded within the rain
   bands, with 0-1 SRH over 500 m2/s2 aiding tornado potential.

   ..Jewell.. 08/27/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...JAN...LIX...LCH...SHV...HGX...

   LAT...LON   29419344 29549419 29929446 30899443 31719432 32069404
               32189368 32239336 32149282 31959231 30629110 30089079
               29529069 29089084 28979111 28999167 29419344

mcd1586.gif

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5 minutes ago, Dunkman said:

I mean the dropsonde caught 128kts in that pass with Laura. I don't really know enough about SFMR calibration studies to comment but the discussion doesn't seem relevant to this storm based on the dropsonde and radar data we have.

SFMR is used extensively in many hurricanes now, so I would think it would be at leastsomewhat relevant.  And dropsondes have limitations as well.  They measure instantaneous wind, not a 1-min avg, so it is not as straightforward as the raw data shows.  It has to go through QC and other checks before it is considered a representative wind measurement. 

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6 minutes ago, WeatherNC said:
Mesoscale Discussion 1586
   NWS Storm Prediction Center Norman OK
   0747 PM CDT Wed Aug 26 2020

   Areas affected...much of Louisiana...far eastern Texas and southwest
   Mississippi

   Concerning...Tornado Watch 452...

   Valid 270047Z - 270245Z

   The severe weather threat for Tornado Watch 452 continues.

   SUMMARY...Shear will continue to increase with the approach of
   Hurricane Laura, with sporadic tornadoes possible within developing
   bands of storms through tonight. The greatest tornado risk will
   exist within the northeastern quadrant of the storm, primarily over
   Louisiana. As such, a new tornado watch will be needed.

   DISCUSSION...Objective analysis shows gradually increasing low-level
   shear over the area, with 0-1 SRH of 300-400 m2/s2 across southwest
   Louisiana early this evening. Shear will increase overnight as
   Hurricane Laura continues northward toward coastal Louisiana and
   Texas. Low-level moisture quality will also increase near and east
   of the center track, with dewpoints at or above 77 F. This should
   result in favorable SBCAPE for supercells embedded within the rain
   bands, with 0-1 SRH over 500 m2/s2 aiding tornado potential.

   ..Jewell.. 08/27/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...JAN...LIX...LCH...SHV...HGX...

   LAT...LON   29419344 29549419 29929446 30899443 31719432 32069404
               32189368 32239336 32149282 31959231 30629110 30089079
               29529069 29089084 28979111 28999167 29419344

mcd1586.gif

It makes sense since the core of the storm is coming in, so that is an automatic increase in a tornado threat.  Also the mini supercells near Greater NOLA and BR are constantly rotating as well.  A new long term tornado watch until 6AM would be appropriate for that area.

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4 minutes ago, vortex95 said:

SFMR is used extensively in many hurricanes now, so I would think it would be at leastsomewhat relevant.  And dropsondes have limitations as well.  They measure instantaneous wind, not a 1-min avg, so it is not as straightforward as the raw data shows.  It has to go through QC and other checks before it is considered a representative wind measurement. 

The fl and dropsonde data also supports the intensity. The sfmr is not inconsistent with that. 

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130 kts seems reasonable. I'm a little scathing though. I'd like sound SFMR beyond 140 kts before I am comfortable with an upgrade. It's semantics though. This is an incredibly intense cyclone.

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11 minutes ago, KoalaBeer said:

Yup. As bad and as horrifying as Laura will be, I couldn't shake the thought today that Laura could of been one of, if not the worst natural disaster in US history if it came ashore 100 miles or so west into the Houston metro. This is of course no condolence to the folks about to lose everything in SW Louisiana. 

Along parts of the S LA coastline sea level may sit at just 5 ft as much as 50 MI in though. Also, the swampiness of the area would slow down the weakening process compared to hitting an area with more dry land. Andrew was still Cat 4 (I think) after crossing S FL because of the Everglades. 

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Just now, Windspeed said:

130 kts seems reasonable. I'm a little scathing though. I'd like sound SFMR beyond 140 kts before I am comfortable with an upgrade. It's semantics though. This is an incredibly intense cyclone.

NHC will upgrade it posthumously like they did Michael 

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Just now, Windspeed said:

130 kts seems reasonable. I'm a little scathing though. I'd like sound SFMR beyond 140 kts before I am comfortable with an upgrade. It's semantics though. This is an incredibly intense cyclone.

I agree with this.  Upgrade to cat 5 probably means confident SFMR > 140, perhaps with dropsonde support.  We definitely don't have that yet.

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14 minutes ago, OSUmetstud said:

Yeah. I was more commenting on the need to throw 100 different warning at people. It just seems like too much. 

That particular WFO presentation area has always been 'overload' when there's a lot going on. It's a 2-dimensional graphic of a 3 or 4 dimensional reality/display. I don't see NOAA changing it.

Just next to it's upper right corner and down alongside [on an WFO mainpage] there are descriptive condition/status links. I just pick through them as needed.

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Just now, the ghost of leroy said:

NHC will upgrade it posthumously like they did Michael 

There were numerous indicators of > 140 kt in the case of Michael.  We haven't seen that yet here.

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There were numerous indicators of > 140 kt in the case of Michael.  We haven't seen that yet here.

Bingo. Sorry for the historical stuff continuing but in Laura's case this is our most recent close comparison, not meaning geographically related either, though obviously that counts too.

 

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There is obviously still time, and pressure seems to still be falling.  New recon is inbound, so lets see what they find in the NW quad.  But I doubt there will even be a post-season upgrade unless there is something unflagged > 140 combined with dropsonde data that at least implicitly supports this intensity.

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2 minutes ago, jpeters3 said:

There were numerous indicators of > 140 kt in the case of Michael.  We haven't seen that yet here.

It's annoying we haven't gotten a NE eye wall pass by recon in the last hour. 

Factoring in the forward motion and Obs through the other more recent eyewall intercepts, I'm guessing it's holding 140kt+ surface winds now.

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