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Possible late season severe outbreak morning of 10/8/14


CoastalWx

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The cool thing about the EF Scale (that drives many people nuts) is that it's a moving target. It is constantly being improved upon, and one of the major initiatives is to include more science in the tree damage indicators. Elms differ in strength from oaks, and white pine from fir, etc. It isn't as cut and dry and hardwood/softwood.

 

Likewise, we're always finding new damage indicators to include.

 

Does the NWS consult with specialists when it comes to assessing damage or do they strictly rely on in-house staff to make that determination?  I'm certainly not a tree specialist but I do know that trees have varying densities and hardnesses and as Eek said will become stronger in the prevailing winds but when a strong enough wind comes in an other direction they'll break readily.

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Do you happen to know what species of pine that number was based on?  

 

White pines are amazing... they can take a lot of wind if it comes from the dominant direction, but if comes from the opposite direction, they shed branches as if they were only held on by velcro.

 

I vividly remember hurricane bob had a couple random gusts from the east (probably 40mph?) that stripped probably a 1/3rd of the limbs off of one pine at the end of a clump.   Same group of pines was unbothered by my 55mph gust a few years ago.  (82.5MPH in BCI units)

 

I'm sure there is documentation out there, but I personally have no knowledge of if that was an individual species or an average of multiple (which is my guess). I do agree with your assessment regarding prevailing wind versus "freak" directions.

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The cool thing about the EF Scale (that drives many people nuts) is that it's a moving target. It is constantly being improved upon, and one of the major initiatives is to include more science in the tree damage indicators. Elms differ in strength from oaks, and white pine from fir, etc. It isn't as cut and dry and hardwood/softwood.

 

Likewise, we're always finding new damage indicators to include.

 

That's really cool, Chris. I think you're right that that's a huge strength of the EF scale. Soon you guys will need to be arborists to assign EF values lol

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Does the NWS consult with specialists when it comes to assessing damage or do they strictly rely on in-house staff to make that determination?  I'm certainly not a tree specialist but I do know that trees have varying densities and hardnesses and as Eek said will become stronger in the prevailing winds but when a strong enough wind comes in an other direction they'll break readily.

 

Absolutely they do, especially with the EF Scale wind estimates. For the surveys themselves, unless there is reason to believe it was greater than EF3 there usually isn't any sort of structural specialist (engineering or otherwise) along for the ride, unless you're in Oklahoma, Kansas, or Texas near their research labs.

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Absolutely they do, especially with the EF Scale wind estimates. For the surveys themselves, unless there is reason to believe it was greater than EF3 there usually isn't any sort of structural specialist (engineering or otherwise) along for the ride, unless you're in Oklahoma, Kansas, or Texas near their research labs.

I did a graduate paper on forest blowdown in 1993, remember this paper though

Topography: Topographic exposure has been shown to have major effects on wind damage

at the landscape scale. In a Jamaican forest Bellingham (1991) found higher damage on

southern slopes and ridge crests that were exposed to the hurricane-face winds, while minor

damage occurred on protected northern slopes. Boose and others (1992) found a similar

pattern of hurricane damage in New England, USA; higher damage occurred on

southwestern slopes exposed to the hurricane winds, whereas minor damage occurred in a

protected deep valley. They concluded that topographic exposure, combined with wind

intensity and forest stand attributes, could largely explain damage patterns at landscape

scale

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There is a lot that goes into wind speeds, but 150 will leave nothing behind really..esp pine and hardwood. Highly doubt it was that strong. Could have been 100-120 or so.

Yeah, I'm basing my thinking on checking the damage in Punta Gorda, FL after 140-170 gusts (NWS/Measured) and while the area was absolutely devastated, it wasn't complete mowage like the Mt. Tom.  New England trees are certainly less able to stand up to wind so that's a factor for sure.  I'm probably unlikely to out-guess the experts on this one.  I don't know though still, that Mt. Tom damage is amazing all in one gust.  I wish there was an instrument there to record it.

 

edit, I remembered after posting seeing an area that was exposed to the harbor where there was complete damage to all the trees.  Probably exposure makes a big difference and explains the sporadic damage I was mentioning above away from the water.

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