baroclinic_instability Posted February 11, 2011 Share Posted February 11, 2011 A potentially significant downslope windstorm event is brewing for the lee of the Continental Divide in northern MT with the approach of a strong low amplitude shortwave and associate upper level jet streak. Cross barrier flow is nearly uniformly west-southwesterly and perfectly perpendicular to the divide/Lewis Range, and the flow is strongly stable with weak vertical wind shear. It does seem that the froude number will be sufficient for the development of strong vertically propagating mountain waves and the potential for developing mid-level critical layers. NAM soundings show a very stable layer needed for the maintenance of large propagating mountain waves--and the weak vertical wind shear above ridgetop (7000-9000 feet in northern MT) should keep the wave mode vertically propagating as opposed to trapped. Also note the critical layer the NAM develops in response to wave overturning around 500 hpa. The wind fields underneath the overturned layer are ridiculous as a result--up to 100+ knots. Pretty impressive stuff. The layer just above mountaintop shows off the chart downslope flow in response--and strong downslope winds will likely make it well into the high plains. The northern MT region is also in a great location in the subsident portion of the mesoscale jet streak circulation which should act to maintain large propagating mountain waves. The NAM shows how far the downslope winds may progress through the plains with a strong region of enhanced vertical forcing well downwind of the mountain range. This is not a trapped wave but instead a hydraulic jump--and it exists well past Cutbank, MT. Pretty impressive stuff really. http://en.wikipedia..../Hydraulic_jump In other words--pretty significant windstorm is potentially on its way for northern/central MT with some rather insane wind gust potential. However--forecast still needs to be monitored--especially the stability profile/wind shear as well as how far south the shortwave develops as the NAM is currently stronger/more amplified than the GFS/Euro. Anyone who has ever tried to forecast these beasts know how challenging these events are. Link to comment Share on other sites More sharing options...
CO 4X4 Posted February 11, 2011 Share Posted February 11, 2011 This is my first posting here, I used to be one of the few CO posters on easternuswx. Thanks for the excellent analysis. It will be windy as well this weekend along the Colorado Front Range. As usual, windy conditions are coinciding with a big transition in our general WX pattern, from the teens and subzero the last two weeks to mid to upper 50s next week. I am also noticing this is coinciding with a quick change in the PNA. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 11, 2011 Author Share Posted February 11, 2011 This is my first posting here, I used to be one of the few CO posters on easternuswx. Thanks for the excellent analysis. It will be windy as well this weekend along the Colorado Front Range. As usual, windy conditions are coinciding with a big transition in our general WX pattern, from the teens and subzero the last two weeks to mid to upper 50s next week. I am also noticing this is coinciding with a quick change in the PNA. Welcome--it is good having intermountain W posters in here--we don't have enough of them. As for you--a definite big change. You guys are lucky to have the Rockies to help usher in the change a lot quicker! But yeah--definitely the beginning of a pretty distinct pattern change in the Pacific and redistribution of the Polar air mass. Link to comment Share on other sites More sharing options...
aslkahuna Posted February 11, 2011 Share Posted February 11, 2011 Ah yes, the Chinook finally shows up. Steve Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2011 Author Share Posted February 12, 2011 It is just the beginning--but a gorgeous wave cloud is already setting up along the entire continental divide in Montana. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2011 Author Share Posted February 12, 2011 The wave cloud associated with the mountain wave streaking across the Livingston sky: Link to comment Share on other sites More sharing options...
CO 4X4 Posted February 12, 2011 Share Posted February 12, 2011 Never been to MT, but those clouds look awfully familiar.. Starting to look springlike. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2011 Author Share Posted February 12, 2011 Never been to MT, but those clouds look awfully familiar.. Starting to look springlike. Agreed--I like this type of weather pattern. We haven't seen much of this type of pattern setup all winter long. A nice change. Link to comment Share on other sites More sharing options...
mnweather Posted February 12, 2011 Share Posted February 12, 2011 How much damage from wind do they get from this? WOW at 55-85 mph. There has got to be some damage. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2011 Author Share Posted February 12, 2011 How much damage from wind do they get from this? WOW at 55-85 mph. There has got to be some damage. Not really a lot of structural since it is so rural out there--more related to travel since two major roads run straight N-S in that region--I15 and 89/287. Cross winds like that can blow over semis quite easily--and if strong enough--even cars/trucks can have significant travel issues. Some structural damage is a threat though--nothing widespread though. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 12, 2011 Share Posted February 12, 2011 Took a vacation out to northwest MT like 5 years ago staying in Big Fork, MT and visited glacier national park, very cool place to be. Stayed at a house on a lake in July getting into the upper 80's/90's during the day but dropping into the 40's at night. Great analysis Baro. Link to comment Share on other sites More sharing options...
CO 4X4 Posted February 12, 2011 Share Posted February 12, 2011 How much damage from wind do they get from this? WOW at 55-85 mph. There has got to be some damage. Here's the oddity of it all. I regularly see Chinook winds of 100 MPH in the spring. There's been straight line winds of 150 MPH around here in the mountains. On one occasion near Boulder, I was sheltering in my pickup truck at a mountain job site when a gust came up that shattered the back window. Had to crawl on the ground, impossible to stand. Yet, in spite of these more or less regular occurrences, the damage around here seems minimal compared to if the same winds hit elsewhere. 55 MPH is just a spring breeze. There are different building codes in Colorado than other places. I built this place 12 years ago, playing general contractor. The county demanded that I install what's called Simpson straps from the building timbers to the concrete foundation to hold it down in high winds. Thick steel straps bolted into both the timber and into the concrete. Unheard of where I grew up in Illinois ."Doesn't a house weigh enough?" Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 12, 2011 Author Share Posted February 12, 2011 Gusts hitting 80 MPH already in southern Alberta near the MT line--this thing is barely getting started and already some impressive gusts. CWGM 121700Z AUTO 24047G70KT 07/M08 RMK AO1 9PAST HR M PK WND 25070/1651 P0007 T00721076 50019 CWGM 121600Z AUTO 24049G72KT 07/M09 RMK AO1 PK WND 23083/1501 T00721091 CWGM 121500Z AUTO 24051G72KT 07/M09 RMK AO1 PK WND 24076/1434 T00681089 Link to comment Share on other sites More sharing options...
L.B. LaForce Posted February 12, 2011 Share Posted February 12, 2011 Absolutely incredible! 21z RUC bufkit soundings are insane. Just look at the omega profiles for LRR (getting downslope flow) and then CTB getting the hydraulic jump. Link to comment Share on other sites More sharing options...
OHSnow Posted February 12, 2011 Share Posted February 12, 2011 Is this the Bastardi thermonuclear storm? Link to comment Share on other sites More sharing options...
L.B. LaForce Posted February 12, 2011 Share Posted February 12, 2011 ime: 2011-02-12 17:21 UTC Event: 74 HIGH SUST WINDS Source: mesonet Remark: wind gusts of 101 mph at the deep creek raws site at both 821 am mst and 1021 am mst. sustained winds were between 68 and 74 mph during this time as well...with the 74 mph sustained wind occurring at 921 am mst. Link to comment Share on other sites More sharing options...
OHSnow Posted February 12, 2011 Share Posted February 12, 2011 Gusts hitting 80 MPH already in southern Alberta near the MT line--this thing is barely getting started and already some impressive gusts. CWGM 121700Z AUTO 24047G70KT 07/M08 RMK AO1 9PAST HR M PK WND 25070/1651 P0007 T00721076 50019 CWGM 121600Z AUTO 24049G72KT 07/M09 RMK AO1 PK WND 23083/1501 T00721091 CWGM 121500Z AUTO 24051G72KT 07/M09 RMK AO1 PK WND 24076/1434 T00681089 I see an 83 knot wind gust in there -- that has to be like 90 mph, I'd imagine. Link to comment Share on other sites More sharing options...
Analog96 Posted February 12, 2011 Share Posted February 12, 2011 The wave cloud associated with the mountain wave streaking across the Livingston sky: You're in Montana? All this time I thought you were in Minnesota. Link to comment Share on other sites More sharing options...
Analog96 Posted February 12, 2011 Share Posted February 12, 2011 I see an 83 knot wind gust in there -- that has to be like 90 mph, I'd imagine. 83 kt is close to 100 MPH. Link to comment Share on other sites More sharing options...
Hoosier Posted February 12, 2011 Share Posted February 12, 2011 I see an 83 knot wind gust in there -- that has to be like 90 mph, I'd imagine. more like 95 mph Link to comment Share on other sites More sharing options...
Analog96 Posted February 12, 2011 Share Posted February 12, 2011 more like 95 mph Yeah, I think it comes out to 97 MPH. Link to comment Share on other sites More sharing options...
NIUmetGF Posted February 13, 2011 Share Posted February 13, 2011 RWIS Obs from Pendroy, MT Site Time Tmp Dpt %RH W/H Wdr Wsp Wgs Pres Vis Prate Pacc Pint/Ptype MTPND Feb 12 2139UTC 54 14 19 SE 7 11 0.000 0.000 None None MTPND Feb 12 2210UTC 53 13 19 E 9 20 0.000 0.000 None None MTPND Feb 12 2241UTC 46 16 28 W 56 75 0.000 0.000 Unknown Unknown MTPND Feb 12 2307UTC 49 18 28 W 71 96 0.000 0.000 Unknown Unknown MTPND Feb 12 2340UTC 48 18 29 W 79 93 0.000 0.000 Unknown Unknown MTPND Feb 13 0011UTC 47 19 32 W 73 90 0.000 0.000 Unknown Unknown MTPND Feb 13 0038UTC 46 20 34 W 73 91 0.000 0.000 Unknown Unknown Link to comment Share on other sites More sharing options...
NIUmetGF Posted February 13, 2011 Share Posted February 13, 2011 Cutbank, MT Site Time Tmp Dpt %RH W/H Wdr Wsp Wgs Cld Ceilg MSLP 1hPn 6hX 6hN Vis Wx KCTB Feb 12 1656UTC 45 22 40 WSW 31 39 CLR UNL 1008.1 10.00 KCTB Feb 12 1756UTC 46 23 40 WSW 26 36 CLR UNL 1007.9 46 38 10.00 KCTB Feb 12 1856UTC 46 23 40 WSW 29 40 CLR UNL 1007.3 10.00 KCTB Feb 12 1956UTC 47 22 37 WSW 53 68 CLR UNL 1004.7 10.00 KCTB Feb 12 2056UTC 49 23 36 W 30 48 CLR UNL 1004.3 10.00 KCTB Feb 12 2156UTC 49 21 33 W 38 47 CLR UNL 1002.9 10.00 KCTB Feb 12 2256UTC 50 20 30 WNW 10 CLR UNL 1002.8 10.00 KCTB Feb 12 2356UTC 48 21 34 W 44 62 CLR UNL 1000.1 50 45 10.00 KCTB Feb 13 0056UTC 47 23 38 WSW 57 74 CLR UNL 997.7 10.00 Link to comment Share on other sites More sharing options...
Chicago Storm Posted February 13, 2011 Share Posted February 13, 2011 0624 PM NON-TSTM WND GST 1 NE CHOTEAU 47.82N 112.17W 02/12/2011 M114 MPH TETON MT TRAINED SPOTTER LAST WIND REPORT FROM CHOTEAU AIRPORT FOR AWHILE...ANEMOMETER BLEW AWAY Link to comment Share on other sites More sharing options...
cmichweather Posted February 13, 2011 Share Posted February 13, 2011 0624 PM NON-TSTM WND GST 1 NE CHOTEAU 47.82N 112.17W 02/12/2011 M114 MPH TETON MT TRAINED SPOTTER LAST WIND REPORT FROM CHOTEAU AIRPORT FOR AWHILE...ANEMOMETER BLEW AWAY lol really???? Link to comment Share on other sites More sharing options...
Analog96 Posted February 13, 2011 Share Posted February 13, 2011 lol really???? It's real. It's in the PNS! Link to comment Share on other sites More sharing options...
SpartyOn Posted February 13, 2011 Share Posted February 13, 2011 0624 PM NON-TSTM WND GST 1 NE CHOTEAU 47.82N 112.17W 02/12/2011 M114 MPH TETON MT TRAINED SPOTTER LAST WIND REPORT FROM CHOTEAU AIRPORT FOR AWHILE...ANEMOMETER BLEW AWAY They are not cheap either..lol Whats the wind speed that can rip a device off a metal or wood pole...100mph +++ Link to comment Share on other sites More sharing options...
Analog96 Posted February 13, 2011 Share Posted February 13, 2011 They are not cheap either..lol Whats the wind speed that can rip a device off a metal or wood pole...100mph +++ usually around 125 from what i heard. Link to comment Share on other sites More sharing options...
cmichweather Posted February 13, 2011 Share Posted February 13, 2011 It's real. It's in the PNS! haha ya i was just suprised this wasn't a mount washington type reading wasn't up in the mtns but from the downslope flow. That's a hell of a wind gust. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 13, 2011 Author Share Posted February 13, 2011 You're in Montana? All this time I thought you were in Minnesota. I am in MN heading to North Platte--but I love all weather--especially mountain weather! Link to comment Share on other sites More sharing options...
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