Current Radar or Satellite Image

Flhurricane.com - Central Florida Hurricane CenterHurricanes Without the Hype! Since 1995


Azores #96L fails to complete transition into a Sub-Tropical Storm. Elsewhere, weak low pressure in Caribbean may linger into next week.
Days since last H. Landfall - US: Any 47 (Nate) , Major: 64 (Maria) Florida - Any: 74 (Irma) Major: 74 (Irma)
None
COMMUNICATION
STORM DATA
CONTENT
FOLLOW US
ADS
Login to remove ads

 


News Talkback >> 2017 News Talkbacks

BloodstarModerator
Moderator


Reged: Mon
Posts: 434
Loc: Georgia Tech
Re: Hurricane Harvey Strengthening and Approaching Texas
      Fri Aug 25 2017 12:55 PM

Quote:

Quote:

I noticed a similar phenomenon monitoring Matthew last year. The winds aloft, that are taken to be the true measure of the storm, aren't at all the winds that reach to the ground.




I've noticed this in multiple hurricanes over the years. Not sure how the NHC calculates the differences between flight level and surface winds but it appears their ratio is wrong -OR- combined with the 8 min average vs the 1 min average the numbers are radically different.

I've always though the NHC should adjust the "estimated" winds down to true wind speed once they had good ground based data (buoys or other known calibrated weather stations). However they seem to stick with flight level winds. I do believe some of this is CYA, better to estimate high then to give people a false sense of security with a Cat lower forecast. In the past I've seen report of gusts, micro bursts, mini-tornados, down drafts and other small-scale higher intensity winds in certain areas due localized environmental conditions during land falling 'canes.




The difference between a 1 minute average and an 8 or 10 minute average is actually pretty dramatic. I'm not sure which one would be most 'representative' of the storms potential damage.

The issue with surface winds as a ratio of winds aloft is because of turbulence and how well the wind 'mixes' down towards the surface. Also of note, the 'surface isn't defined as the actual surface (but instead 2 or 10 meters above the actual surface). which is why there is often a difference in the wind speeds at the theoretical surface versus the actual surface.

Trying to model actual surface condition (as opposed to 2 or 10 meters up) is incredibly difficult, you have all sorts of microscale phenomena to deal with, such as frictional forces and turbulence from objects, which makes the modeling that much more problematic.

As far as mixing from the "upper levels" (850mb and lower pressures), There are lots of papers on TC wind mixing exploring that very issue. Since TC winds are not well mixed, some of the questions that is still being answered are: how do the winds aloft mix down to the surface and when can the mixing ratios of winds aloft be applied to determine surface winds?

(At least, I don't think there are definitive answers on those...)

So in short, they don't actually simply stick with flight level winds, They use surface obs when possible, only resorting to ratio estimates when there isn't any other option. And because of the nature of the winds, that there is a lot of variability in wind speeds even in locations that are relatively close to each other spatially. which can make a wind forecast look bad even though it's representative of the maximum wind speeds in that area instead of every single location in that area.

--------------------
M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2018.

Post Extras Print Post   Remind Me!     Notify Moderator


Entire topic
Subject Posted by Posted on
* Harvey Makes Landfall at Cat 4 MikeCAdministrator Fri Aug 25 2017 12:55 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas Psyber   Sat Aug 26 2017 02:28 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Sat Aug 26 2017 02:27 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Sat Aug 26 2017 01:05 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Sat Aug 26 2017 12:02 AM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas JMII   Fri Aug 25 2017 11:13 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas Prospero   Fri Aug 25 2017 10:02 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Fri Aug 25 2017 09:57 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas JMII   Fri Aug 25 2017 09:11 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Fri Aug 25 2017 08:13 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas Prospero   Fri Aug 25 2017 08:13 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Fri Aug 25 2017 07:55 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas Prospero   Fri Aug 25 2017 07:43 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Fri Aug 25 2017 07:21 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas JMII   Fri Aug 25 2017 05:47 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas Psyber   Fri Aug 25 2017 05:29 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas JMII   Fri Aug 25 2017 05:03 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Fri Aug 25 2017 04:51 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas Psyber   Fri Aug 25 2017 04:44 PM
. * * Re: Hurricane Harvey Now a Major Hurricane cieldumortModerator   Fri Aug 25 2017 04:35 PM
. * * Re: Hurricane Harvey Nearly a Major Hurricane This Morning MikeCAdministrator   Fri Aug 25 2017 02:40 PM
. * * Re: Hurricane Harvey Nearly a Major Hurricane This Morning BloodstarModerator   Fri Aug 25 2017 01:22 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas BloodstarModerator   Fri Aug 25 2017 12:55 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Fri Aug 25 2017 12:41 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas cieldumortModerator   Fri Aug 25 2017 12:41 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas JMII   Fri Aug 25 2017 12:23 PM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas ERA   Fri Aug 25 2017 10:41 AM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas ERA   Fri Aug 25 2017 10:40 AM
. * * Re: Hurricane Harvey Nearly a Major Hurricane This Morning MikeCAdministrator   Fri Aug 25 2017 10:18 AM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas Myles   Fri Aug 25 2017 09:55 AM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas ERA   Fri Aug 25 2017 09:47 AM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas MikeCAdministrator   Fri Aug 25 2017 07:12 AM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas cieldumortModerator   Fri Aug 25 2017 01:26 AM
. * * Re: Hurricane Harvey Strengthening and Approaching Texas cieldumortModerator   Fri Aug 25 2017 01:19 AM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf MikeCAdministrator   Fri Aug 25 2017 12:07 AM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf MikeCAdministrator   Thu Aug 24 2017 09:23 PM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf danielwAdministrator   Thu Aug 24 2017 04:53 PM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf MikeCAdministrator   Thu Aug 24 2017 03:06 PM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf cieldumortModerator   Thu Aug 24 2017 01:26 PM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf Psyber   Thu Aug 24 2017 01:13 PM
. * * Re: Tropical Storm Harvey Strengthening and Approaching Texas MikeCAdministrator   Thu Aug 24 2017 11:41 AM
. * * Re: Tropical Storm Harvey Strengthening and Approaching Texas MikeCAdministrator   Thu Aug 24 2017 10:35 AM
. * * Re: Tropical Storm Harvey Strengthening and Approaching Texas cieldumortModerator   Thu Aug 24 2017 10:21 AM
. * * Re: Tropical Storm Harvey Strengthening and Approaching Texas MikeCAdministrator   Thu Aug 24 2017 10:00 AM
. * * Re: Tropical Storm Harvey Strengthening and Approaching Texas cieldumortModerator   Thu Aug 24 2017 07:56 AM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf MikeCAdministrator   Thu Aug 24 2017 07:50 AM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf cieldumortModerator   Thu Aug 24 2017 12:10 AM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf MikeCAdministrator   Wed Aug 23 2017 10:10 PM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf MikeCAdministrator   Wed Aug 23 2017 05:31 PM
. * * Re: Harvey Regenerates for Gulf Watches/Warnings up for Western Gulf cieldumortModerator   Wed Aug 23 2017 11:55 AM
. * * Re: Remnants of Harvey Likely to Regenerate in the Gulf MikeCAdministrator   Wed Aug 23 2017 11:46 AM
. * * Re: Remnants of Harvey Likely to Regenerate in the Gulf MikeCAdministrator   Wed Aug 23 2017 08:51 AM
. * * Re: Remnants of Harvey Likely to Regenerate in the Gulf MikeCAdministrator   Wed Aug 23 2017 07:52 AM
. * * Re: Remnants of Harvey Likely to Regenerate in the Gulf Nick Humphrey   Wed Aug 23 2017 02:30 AM

Extra information
0 registered and 9 anonymous users are browsing this forum.

Moderator:  CFHC, MikeC, Ed Dunham, Colleen A., danielw, Clark, RedingtonBeachGuy, SkeetoBite, Bloodstar, tpratch, typhoon_tip, cieldumort 



Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled

Rating:
Thread views: 11949

Rate this thread

Jump to

Note: This is NOT an official page. It is run by weather hobbyists and should not be used as a replacement for official sources. 
CFHC's main servers are currently located at Hostdime.com in Orlando, FL.
Image Server Network thanks to Mike Potts and Amazon Web Services. If you have static file hosting space that allows dns aliasing contact us to help out! Some Maps Provided by:
Great thanks to all who donated and everyone who uses the site as well. Site designed for 800x600+ resolution
When in doubt, take the word of the National Hurricane Center