MikeC
Admin
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Loc: Orlando, FL
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Mandatory evacuations have been issued for portions of the following areas:
- The city of Port Aransas
- Aransas County
- Refugio County
- San Patricio County
- Victoria County
- Calhoun County
- Kleberg County
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cieldumort
Moderator
Reged: Mon
Posts: 2305
Loc: Austin, Tx
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With recon finding Harvey now a 100 MPH Cat 2, the following local Watch/Warning Statement/Advisories take on extra significance.
Two samples of select cities this and subsequent post (One along the coast, the other well inland)..
Sample Watch/Warning/Advisory from along the coast
Matagorda-
1027 PM CDT Thu Aug 24 2017
...HURRICANE WARNING REMAINS IN EFFECT...
...STORM SURGE WARNING REMAINS IN EFFECT...
* WIND
- LATEST LOCAL FORECAST: Equivalent Tropical Storm force wind
- Peak Wind Forecast: 35-45 mph with gusts to 60 mph
- Window for Tropical Storm force winds: early Friday afternoon until Monday morning
- CURRENT THREAT TO LIFE AND PROPERTY: Extreme
- The wind threat has remained nearly steady from the previous assessment.
- Emergency plans should include a reasonable threat for major hurricane force wind greater than 110 mph of equivalent Category 3 intensity or higher.
- To be safe, aggressively prepare for the potential of devastating to catastrophic wind impacts. Remaining efforts to secure properties should now be brought to completion.
- Extremely dangerous and life-threatening wind is possible. Failure to adequately shelter may result in serious injury, loss of life, or immense human suffering. Move to safe shelter before the wind becomes hazardous.
- POTENTIAL IMPACTS: Devastating to Catastrophic
- Structural damage to sturdy buildings, some with complete roof and wall failures. Complete destruction of mobile homes. Damage greatly accentuated by large airborne projectiles. Locations may be uninhabitable for weeks or months.
- Numerous large trees snapped or uprooted along with fences and roadway signs blown over.
- Many roads impassable from large debris, and more within urban or heavily wooded places. Many bridges, causeways, and access routes impassable.
- Widespread power and communications outages.
* STORM SURGE
- LATEST LOCAL FORECAST: Life-threatening storm surge possible
- Peak Storm Surge Inundation: The potential for 7-11 feet above ground somewhere within surge prone areas
- Window of concern: Begins Friday morning
- CURRENT THREAT TO LIFE AND PROPERTY: Extreme
- The storm surge threat has remained nearly steady from the previous assessment.
- Emergency plans should include a reasonable threat for extreme storm surge flooding greater than 9 feet above ground.
- To be safe, aggressively prepare for the potential of devastating to catastrophic storm surge flooding impacts. Evacuation efforts should now be brought to completion. Evacuations must be complete before driving conditions become unsafe.
- Life-threatening inundation is possible. Failure to heed evacuation orders may result in serious injury, significant loss of life, or immense human suffering. Leave if evacuation orders are given for your area. Consider voluntary evacuation if recommended. Poor decisions may result in being cut off or needlessly risk lives.
- POTENTIAL IMPACTS: Devastating to Catastrophic
- Widespread deep inundation, with storm surge flooding greatly accentuated by powerful battering waves. Structural damage to buildings, with many washing away. Damage greatly compounded from considerable floating debris. Locations may be uninhabitable for an extended period.
- Near-shore escape routes and secondary roads washed out or severely flooded. Flood control systems and barriers may become stressed.
- Extreme beach erosion. New shoreline cuts possible.
- Massive damage to marinas, docks, boardwalks, and piers. Numerous small craft broken away from moorings with many lifted onshore and stranded.
* FLOODING RAIN
- LATEST LOCAL FORECAST: Flash Flood Watch is in effect
- Peak Rainfall Amounts: Additional 18-24 inches, with locally higher amounts
- CURRENT THREAT TO LIFE AND PROPERTY: Extreme
- The flooding rain threat has increased from the previous assessment.
- Emergency plans should include a reasonable threat of extreme flooding where peak rainfall totals vastly exceed amounts conducive for flash flooding and rapid inundation. Rescues and emergency evacuations are very likely.
- To be safe, aggressively prepare for the potential of devastating to catastrophic flooding rain impacts.
- Life-threatening flooding is possible. Failure to take action may result in serious injury, significant loss of life, or human suffering. If flood related watches and warnings are issued, heed recommended actions. Poor decisions may result in being cut off or needlessly risk lives. If vulnerable, relocate to safe shelter on higher ground before flood waters arrive.
- POTENTIAL IMPACTS: Devastating to Catastrophic
- Extreme rainfall flooding may prompt numerous evacuations and rescues.
- Rivers and tributaries may overwhelmingly overflow their banks in many places with deep moving water. Small streams, creeks, canals, and ditches may become raging rivers. Flood control systems and barriers may become stressed.
- Flood waters can enter numerous structures within multiple communities, some structures becoming uninhabitable or washed away. Numerous places where flood waters may cover escape routes. Streets and parking lots become rivers of raging water with underpasses submerged. Driving conditions become very dangerous. Numerous road and bridge closures with some weakened or washed out.
* TORNADO
- LATEST LOCAL FORECAST:
- Situation is somewhat favorable for tornadoes
- CURRENT THREAT TO LIFE AND PROPERTY: Elevated
- The tornado threat has remained nearly steady from the previous assessment.
- When implementing emergency plans, include a reasonable threat for isolated tornadoes.
- To be safe, prepare for the potential of limited tornado impacts.
- Listen for tornado watches and warnings. Be ready to shelter quickly if a tornado approaches.
- POTENTIAL IMPACTS: Limited
- The occurrence of isolated tornadoes can hinder the execution of emergency plans during tropical events.
- A few places may experience tornado damage, along with power and communications disruptions.
- Locations could realize roofs peeled off buildings, chimneys toppled, mobile homes pushed off foundations or overturned, large tree tops and branches snapped off, shallow-rooted trees knocked over, moving vehicles blown off roads, and small boats pulled from moorings.
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cieldumort
Moderator
Reged: Mon
Posts: 2305
Loc: Austin, Tx
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Sample Watch/Warning/Advisory from well-inland
Bexar- 1012 PM CDT Thu Aug 24 2017
...TROPICAL STORM WARNING REMAINS IN EFFECT...
* LOCATIONS AFFECTED
- San Antonio
* WIND
- LATEST LOCAL FORECAST: Below tropical storm force wind
- Peak Wind Forecast: 20-30 mph with gusts to 35 mph
- CURRENT THREAT TO LIFE AND PROPERTY: High
- The wind threat has increased from the previous assessment.
- Emergency plans should include a reasonable threat for hurricane force wind of 74 to 110 mph of equivalent Category 1 to 2 intensity.
- To be safe, aggressively prepare for the potential of extensive wind impacts. Remaining efforts to secure properties should now be brought to completion.
- Dangerous and life-threatening wind is possible. Failure to adequately shelter may result in serious injury or loss of life. Move to safe shelter before the wind becomes hazardous.
- POTENTIAL IMPACTS: Extensive
- Considerable roof damage to sturdy buildings, with some having window, door, and garage door failures leading to structural damage. Mobile homes severely damaged, with some destroyed. Damage accentuated by airborne projectiles. Locations may be uninhabitable for weeks.
- Many large trees snapped or uprooted along with fences and roadway signs blown over.
- Some roads impassable from large debris, and more within urban or heavily wooded places. Several bridges, causeways, and access routes impassable.
- Large areas with power and communications outages.
* FLOODING RAIN
- LATEST LOCAL FORECAST: Flash Flood Watch is in effect
- Peak Rainfall Amounts: Additional 8-12 inches, with locally higher amounts
- CURRENT THREAT TO LIFE AND PROPERTY: High
- The flooding rain threat has increased from the previous assessment.
- Emergency plans should include a reasonable threat for major flooding where peak rainfall totals well exceed amounts conducive for flash flooding and rapid inundation. Rescues and emergency evacuations are likely.
- To be safe, aggressively prepare for the potential of extensive flooding rain impacts.
- Life-threatening flooding is possible. Failure to take action may result in serious injury or significant loss of life. If flood related watches and warnings are issued, heed recommended actions. Poor decisions may result in being cut off or needlessly risk lives. If vulnerable, relocate to safe shelter on higher ground before flood waters arrive.
- POTENTIAL IMPACTS: Extensive
- Major rainfall flooding may prompt many evacuations and rescues.
- Rivers and tributaries may rapidly overflow their banks in multiple places. Small streams, creeks, canals, arroyos, and ditches may become dangerous rivers. In mountain areas, destructive runoff may run quickly down valleys while increasing susceptibility to rockslides and mudslides. Flood control systems and barriers may become stressed.
- Flood waters can enter many structures within multiple communities, some structures becoming uninhabitable or washed away. Many places where flood waters may cover escape routes. Streets and parking lots become rivers of moving water with underpasses submerged. Driving conditions become dangerous. Many road and bridge closures with some weakened or washed out.
* TORNADO
- LATEST LOCAL FORECAST:
- Situation is unfavorable for tornadoes
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MikeC
Admin
Reged: Sun
Posts: 4543
Loc: Orlando, FL
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Recon is finding pressure dropping at about 3mb per hour now, 953mb on the last pass (4AM CDT Advisory had it at 967mb)
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ERA
Registered User
Reged: Fri
Posts: 3
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ERA wanted to know Quote:
How do I reconcile the buoy data from the area of Harvey with the hurricane hunter reports? The buoy data of an hour ago shows ~35 mph winds at the Gulf's surface and 20 meters above. For example: http://www.ndbc.noaa.gov/station_page.php?station=42019
Thanks, ERA
In reply. Most buoys are not strategically placed to encounter a tropical cyclone's stronger, let alone strongest, winds. (That's another thing we have recon for). Harvey's maximum 1-min sustained winds are 110 MPH, but this is only in a very small area in the right-front quadrant very close to the eye, and Buoy 42019 is not close to that.
Something else to consider with regard to buoys, unless you see differently, their reported sustained winds are an 8 minute average, which is going to be proportionally lower than the standard 1-minute sustained used in hurricanes and other weather phenomena. One can safely add another 10% to 20% to adjust for this low bias.
- Ciel
Edited by cieldumort (Fri Aug 25 2017 10:07 AM)
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Myles
Weather Hobbyist
Reged: Wed
Posts: 80
Loc: SW FL
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The buoy you linked is about 100 miles away from the center. Hurricane force winds only extend about 35 miles from the center.
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MikeC
Admin
Reged: Sun
Posts: 4543
Loc: Orlando, FL
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Multiple radars, webcams, and more recordings added
Harvey Related flhurricane recordings
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ERA
Registered User
Reged: Fri
Posts: 3
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OK, fair observation. This buoy seems to be very close to Harvey. http://www.ndbc.noaa.gov/station_page.php?station=42045
An hour ago it showed max gusts of ~46 mph, at surface and 20 meters up.
So my question remains, how to reconcile surface buoy readings with the hurricane hunter findings?
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ERA
Registered User
Reged: Fri
Posts: 3
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Thank you, Ciel.
Even with that explanation, there seems to be a large difference between the winds high aloft that the hurricane hunters measure, and what the surface instruments are currently measuring. weather.com had a graphic of surface instruments at 10:10 am CT, and closest to the Harvey was 43 mph and less as you looked northward. That, at the time the winds aloft were 110 mph or so.
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.
Seems like comparing apples and oranges. Using the high-speed winds aloft as a measure of the potential wind damage to things on the ground.
I am not at all writing about the potential for severe flooding due to rain & storm surge. That is very real.
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JMII
Weather Master
Reged: Thu
Posts: 489
Loc: Margate, Florida
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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 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 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.
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South FL Native... experienced many tropical systems, put up the panels for:
David 79 - Floyd 87 - Andrew 92 - Georges 98 - Frances 04 - Wilma 05 - Matthew 16 - Irma 17
Lost our St James City rental property to Ian 22
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cieldumort
Moderator
Reged: Mon
Posts: 2305
Loc: Austin, Tx
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Recon is not merely reporting back winds aloft. They also use very accurate SFMR measurements of the ocean. Combined with very scientifically sound reduction ratios of their flight-level records, as well as countless dropsondes that measure wind speed from flight level all the way down to the surface, and can even report with split-second increments, the Recon data is exceptionally accurate.
As stated above, buoys are *not* typically 'placed' in advance to capture the areas of maximum sustained winds, and also tend to have a low bias, regardless, a result of their using an 8-min average, rather than the standard 1-min average.
It's a great question and discussion, but any more on this subject after this final response needs to be posted in the Hurricane Ask/Tell forum. Let's keep the main page focused on critical details of Harvey's approach.
As a reminder to regular users and a head's up for anyone new to the site, the structure here is that of a forum, not a chat room. We want to keep it clear of most one-liners and 'thank yous,' etc. Good question and thanks are appreciated - can always send private messages 
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Fully vaccinated as of May 2021
(Moderna x2)
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MikeC
Admin
Reged: Sun
Posts: 4543
Loc: Orlando, FL
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KRIS 6 TV Stream https://livestream.com/accounts/16030759/events/4495499
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Bloodstar
Moderator
Reged: Mon
Posts: 462
Loc: Tucson, AZ
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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 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 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.
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M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2020
Brookhaven National Laboratory
U. Arizona PhD Student
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Bloodstar
Moderator
Reged: Mon
Posts: 462
Loc: Tucson, AZ
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Looking at the raw data, they've got an extrapolated surface pressure at 944 mb. and an uncontaminated SMFR of 88 knots just on their first north/south pass. There's really not much to stop the system from continuing to strengthen until near landfall, so another 12 hours or so for Harvey to continue to power up.
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M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2020
Brookhaven National Laboratory
U. Arizona PhD Student
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MikeC
Admin
Reged: Sun
Posts: 4543
Loc: Orlando, FL
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Recon found some 118knot (Category 3) winds on the most recent pass, more than enough for an upgrade.
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cieldumort
Moderator
Reged: Mon
Posts: 2305
Loc: Austin, Tx
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A couple of points
Harvey appears to be stair-stepping into landfall, and thus the very center may very well make absolute landfall north of Corpus - perhaps a good deal north of CC, but yet not north enough to prevent Corpus from actually riding out the eyewall for an extended duration - never getting a 'break' during the pass of the actual eye.
Most importantly, Harvey is anything but a point on a map. Certainly, the eyewall will be like the passing of a many-miles-wide EF3 tornado, perhaps with embedded vortices of its own adding to the eyewall's destructive potential. However, the massive swath of torrential tropical rain, widespread damaging wind, high coastal storm surge, and duration of the entire event - that is what makes Harvey orders of magnitude more dangerous than your run-of-the-mill /Rita/Charlie/Ike, etc. Not a "Run-of-the-mill /Rita/Charlie/Ike." Residents who have not yet evacuated from locations at risk should let that sink in.
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Psyber
Storm Tracker
Reged: Fri
Posts: 231
Loc: Ontario, Canada
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Quote:
As stated above, buoys are *not* typically 'placed' in advance to capture the areas of maximum sustained winds, and also tend to have a low bias, regardless, a result of their using an 8-min average, rather than the standard 1-min average.
As a reminder to regular users and a head's up for anyone new to the site, the structure here is that of a forum, not a chat room. We want to keep it clear of most one-liners and 'thank yous,' etc. Good question and thanks are appreciated - can always send private messages
It's a good question as to why they don't build a better matrix of buoys in the Gulf as they could provide continuous surface level data...something a H/H will never be able to provide. It's been 13 years since a big hit though so investment in infrastructure always seems to be forgotten once the sting goes away.
UPDATE> Did you see the tracking? Even the vaunted track is garbage for days on this one. Scary stuff given on how long it's going to keep churning. At least it appears to be mostly over land while it dumps. Could you imagine it being stuck half on/half off over a port city or *shudder* New Orleans?
It looks to be going to be stuck at a lvl 3 or weak 4. I'm usually a "let's weather this out" kind of person but anybody foolhardy enough to sit under what could be three feet of rain AND storm surge is psycho.
The SST's where it's currently feeding are 87F and with little sheer, this could get worse.
Edited by cieldumort (Fri Aug 25 2017 06:26 PM)
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MikeC
Admin
Reged: Sun
Posts: 4543
Loc: Orlando, FL
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Latest recon suggest Harvey may be nearing Cat 4 strength, it may reach category 4 before landfall.
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JMII
Weather Master
Reged: Thu
Posts: 489
Loc: Margate, Florida
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From the : Hurricane Harvey Advisory Number 22
Quote:
Hurricane-force winds extend outward up to 35 miles (55 km) from the center
That is a pretty narrow band. So the wind is only really strong right around the eye. This might be why some of the data coming in shows lower winds - the core just missed that reporting station. However it still has some time to do another eye wall replacement cycle which normally causes the winds to spread out.
TS winds have reached the shore in the warning areas, it will be all downhill from here.
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South FL Native... experienced many tropical systems, put up the panels for:
David 79 - Floyd 87 - Andrew 92 - Georges 98 - Frances 04 - Wilma 05 - Matthew 16 - Irma 17
Lost our St James City rental property to Ian 22
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Psyber
Storm Tracker
Reged: Fri
Posts: 231
Loc: Ontario, Canada
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Quote:
Latest recon suggest Harvey may be nearing Cat 4 strength, it may reach category 4 before landfall.
Not sure if I can show offsite url's Mike but this one is a fantastic video of what storm surge really is. The waves just keep stacking and stacking and stacking as they keep coming in but they never really go out like normal wave action. The last part of the video really showed what it was really about. People need to understand that the Gulf Coast took over TWENTY FEET of storm surge during . Whole houses (and their owners) were gone, leaving only concrete pads to indicate where there used to be a home(and a family).
Anyways> Link that shows Storm Surge right up close and personal. Last part of video really shows the worst of it.
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The safest way to deal with a potential Hurricane hitting you...is to leave and just not be there at all.
Edited by Psyber (Fri Aug 25 2017 05:33 PM)
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