December 2019 Discussion

[CoastalWx]

1 minute ago, OceanStWx said:

Now that's a troll. 

0.4" at BDL is a good solid advisory for freezing rain. Congrats!

So now we use BDL flat ASOS for ice accretion. 

[OceanStWx]

2 minutes ago, CoastalWx said:

So now we use BDL flat ASOS for ice accretion. 

Good to know BDL is the preferred winter verification location. 

[tamarack]

3 hours ago, OceanStWx said:

Well that's the information we get from utility companies. Their issues don't become widespread until you get ice accretion over 0.33". It's also not necessarily the amount of trees, but the type. If you have a lot of evergreens they evolved to droop branches as the weight increases, allowing snow and ice to slough off. If you have a lot of trees with crowns reaching up (like we plant in developments) they'll struggle when they accumulate ice/snow.

That doesn't mean localized areas aren't going to have it worse than others. But a single point doesn't verify warnings, you need need coverage over half a zone (typically a county).

Drooping branches can shed snow, not so much for ice.  However, that droop allows branches to support other branches.  Also, the needles of higher branches reduce the load on the lower ones, and the drooping branches reduce catchment area.  The upward branching of most deciduous species means any bending under ice increases the catchment area.  (White pine is in a middling position.  It lacks the abundant branching of spruce and fir and thus offers little "load sharing" and while its horizontal branches allow the droop to limit damage, most of the WP - especially those grown in the open as opposed to in full tree cover - have some upward branches, which are usually the first to go as accretion builds. 

In the 1998 ice storm, I didn't see a single evergreen with the main trunk broken though a couple leaning hemlock had been uprooted.  Spruce-fir tended toward zero damage while white pine generally lost some limbs.  At our Hebron lot on Greenwood Hill, where grass stems had accretion the diameter of s soda can, several pines had suffered cascading breakage on one side (generally toward windward) when upper branches failed and started an "avalanche".

[OceanStWx]

1 minute ago, tamarack said:

Drooping branches can shed snow, not so much for ice.  However, that droop allows branches to support other branches.  Also, the needles of higher branches reduce the load on the lower ones, and the drooping branches reduce catchment area.  The upward branching of most deciduous species means any bending under ice increases the catchment area.  (White pine is in a middling position.  It lacks the abundant branching of spruce and fir and thus offers little "load sharing" and while its horizontal branches allow the droop to limit damage, most of the WP - especially those grown in the open as opposed to in full tree cover - have some upward branches, which are usually the first to go as accretion builds. 

In the 1998 ice storm, I didn't see a single evergreen with the main trunk broken though a couple leaning hemlock had been uprooted.  Spruce-fir tended toward zero damage while white pine generally lost some limbs.  At our Hebron lot on Greenwood Hill, where grass stems had accretion the diameter of s soda can, several pines had suffered cascading breakage on one side (generally toward windward) when upper branches failed and started an "avalanche".

I forgot to tag you in my post, because I figured you would have this kind of info. 

[tamarack]

Just now, OceanStWx said:

I forgot to tag you in my post, because I figured you would have this kind of info. 

Thanks.  And just to stir the pot, I have to admit that I generally use the term "ice storm" any time there's enough accretion to affect tree posture, often when it's well short of NWS criteria.  Promise I'll be more careful in the future.    "A day I haven't learned something is a day I've wasted."

[HoarfrostHubb]

I wouldn’t call this event we just had here an ice storm.  A nice glaze of around 0.20-0.25” radially.  Some branches down.   But the ice was a really minor part of the event