Blizzard Winds

[Andrew Khan]

This may seem like a stupid question but, I am wondering how Blizzards get winds up to Hurricane Force.....? I mean just yesterday Denver got winds up 100 MPH...how is this possible? What makes this?

 

[B Ozanne]

This may seem like a stupid question but, I am wondering how Blizzards get winds up to Hurricane Force.....? I mean just yesterday Denver got winds up 100 MPH...how is this possible? What makes this?

What happened in Denver? Where is this data?

 

[Marko Korosec]

Well, hope I am not offtopic...Right now we have 100-110mph winds here with -1°C, nice breeze I must say The pressure is 1029hPa, cities about 100km SW of me have 1020hPa, cities ENE of me have 1040hPa. Also temperature is 7°C less on the NE and about 6°C more on the SW side.

Pressure and temperature gradients are pretty high!

Last winter we had almost 150mph winds, gradients were even higher that time. Actually this is an usual wind here, its called "Bora" if anyone will search for it :wink:

Here is one pic showing few maniac riding gusts ~ 90mph 2 weeks ago

 

[Robert Dewey]

Not sure about the 100MPH in Denver deal, but...

There are a few reasons why strong winds exist. One reason would be a strong pressure gradient. You don't actually need a really deep low to get a strong pressure gradient, you would just need a low pressure and a high pressure situated fairly close together. That produces gradient force winds that can get pretty intense.

The other cause would be strong winds just above the SFC (usually 3-5K FT). If there is strong CAA present in the low levels on the backside of a system, the low level winds can easily be brought down. Generally though, CAA provides sinking air / negative VV's, so that's not really the main player in blizzards (although ground blizzards are a different story)...

Meanwhile, some systems have a combinatin of both - strong pressure gradient near the SFC low, and strong CAA / low level winds a bit further away...

Also, the winds across the Plains states tends to be alot strong since there is less friction from trees, hills, etc.. Areas with significantly higher elevation also experience higher winds for the obvious fact that they are closer (or located in) the higher low/mid level winds.

 

[B Ozanne]

Well, hope I am not offtopic...Right now we have 100-110mph winds here with -1°C, nice breeze I must say The pressure is 1029hPa, cities about 100km SW of me have 1020hPa, cities ENE of me have 1040hPa. Also temperature is 7°C less on the NE and about 6°C more on the SW side.

Pressure and temperature gradients are pretty high!

Last winter we had almost 150mph winds, gradients were even higher that time. Actually this is an usual wind here, its called "Bora" if anyone will search for it :wink:

Here is one pic showing few maniac riding gusts ~ 90mph 2 weeks ago

Do you mean KPH (Kilometers per hour)? Those people don't look like they are standing in 90 MPH winds. It takes all of your strength and concentration to stand in 90mph.

Withouth further elaboration on the Denver situation its impossible to know what you are talking about. Was there a canyon wind event? Those happen in Boulder and along the front range.

 

[Robert Dewey]

I was just looking it up on the 'net... I found a few pages that state typical "Bora" winds are in the 50-80KNT range... The highest "Bora" recorded was back in the mid 1950's with a 125KNT gust.

That's just looking over things briefly though...

I think Marko did mean KPH though... That would still be a 55-70MPH event and would fall right in with average Bora events.

 

[Marko Korosec]

No no, I meant MPH! :wink:

Those maniacs were I and some friends, here is a pic of max gusts 43m/s (=155km/h = 96mph), it was at the same place we were standing on that pic. http://img520.imageshack.us/img520/3341/re...pb2300300cl.jpg
Bill, I don't know where is a problem, but we're used to such gusts and I CAN stand easily.
The problem last winter was when I measured my record gusts ~180km/h (50m/s = 112mph), it was difficult to stand in such gusts because the average speed was pretty low, around 100km/h and such gusts just sweep you to the ground. Its easier with higher average like on the first pic, it was ~130 with gusts around 150km/h.

For the proof of today's gusts you can check this graph for stations here in the SW Slovenia, is it 160km/h+ (100mph) or not? http://img397.imageshack.us/img397/6423/wwwgraf5xp.jpg

Last winter, on Nov. 14th 2004 there was a lot of damage because of Bora wind gusts up to 240km/h (=150mph, thats what I mentioned in previous post) in islands "Krk" and "Hvar" in Croatia. Record for Bora here in Slovenia is also around 240km/h when the TV tower was collapsed 30kms away from here on one hill in the late 60s :wink:

Regards,

 

[Jonathan Merage]

Andrew,

I live about 8 miles south of downtown Denver. I remember seeing a crazy wind reading like that shortly after the cold front passed us on the 7th . Don’t know about what you saw on the 10th :?: , but Denver metro did record a strong gust near 100 mph after that bitter cold Arctic air mass descended south of here. In fact, one of NCAR’s Labs in south-west Boulder (Mesa Lab, 6184 ft ASL) recorded a coupla’ gusts at 90mph!!
www.atd.ucar.edu/cgi-bin/weather.cgi?site=ml&period=weekly&units=english&plotfield=wspd
(left side of chart, between 6-7 days ago), with a coincident pressure drop from 30.30 inHg to just under 29.90 inHg pretty much overnight.

Mountain-Front Interactions & Dynamics 101 :lol: : Combine mountain (or especially foothills) front-induced down-slope winds with strong subsidence beneath the high pressure cold air plummeting south, and you have a near classic setup for strong, gusty, persistent winds for all valleys & high plains areas just east of the front-range foothills.
Hopefully that ‘in-a-nutshell’ explanation will help answer your question. Did I miss anything?

Jon

 

[Rockwell Schrock]

Hey all,

I'm just getting back online after a huge wind event that knocked out our power for two and a half days. Hundreds of trees were down; it was absolutely crazy.

The surface low was centered directly over Cape Cod Bay for most of the day, but as it moved offshore winds quickly picked up. One station recorded a gust of 64 MPH right before the power went out.

Here's a surface map around that time... notice the winds blowing in opposite directions at opposite ends of Cape Cod:
http://www.rap.ucar.edu/weather/surface/di...e=19&duration=0

I believe the wind speed was so high due to the fetch that Cape Cod Bay provided, that is, the winds had a large flat area to pick up speed before slamming into the Cape. I noticed that the worst damage was on the bay side of the Cape, which makes sense. Also, every tree fell the same direction: due west.

Here are a few pics I took just driving around my town, but I've seen much worse since then:
http://www.wunderground.com/wximage/viewsi...ICT#slideanchor
http://www.wunderground.com/wximage/viewsi...=25#slideanchor
http://www.wunderground.com/wximage/viewsi...=25#slideanchor

So, in short: I think that geographic features have a major influence.