11/9/05: WIND EVENT (another "witch of november")

[nickgrillo]

Significant synoptic wind event can once again occur with the passage of this upcoming system on WED afternoon and evening. The low deepens rapidly during a 18hr timeframe... With the 989mb surface low pressure being over the US/Canada border according to NAM (near the U.P. of MI) by 18z WED and then pushing about a 150 miles to the east by 0z THUR (with the GFS being nearly identical, except the NAM deepens the low by about 2-3 more millibars). NAM also shows a nice 850mb jet of >50kts in a region of CAA covering all of MI. Depending on how much winds can mix down to the surface through daytime heating, this could become another classic "witch of November" wind event tomorrow. If the dry air can indeed get rid of cloud cover behind the front to get better insolation, I would expect to see sfc wind gusts in the 55-70MPH range across the state of MI tomorrow afternoon and evening.

 

[Jeremy Lemanski]

Nick, did you see the new dis. out of GRR and DTX? They both pulled the trigger saying severe weather tonight with dtx saying this:"ALL
OF THE INGREDIENTS ARE COMING TOGETHER FOR SUPERCELLULAR SEVERE
THUNDERSTORMS POTENTIALLY IMPACTING SE MICHIGAN" and GRR saying this:"IF SURFACE BASED
INSTABILITY COULD DEVELOP WITH SOME 3KM CAPE...THEN THE TOR THREAT
WOULD INCREASE QUICKLY."

I'm pretty surprised myself, considering the tornado/wind threat depends on some surface based storms, i was expecting a toned down discussion, not this.

 

[nickgrillo]

Nick, did you see the new dis. out of GRR and DTX? They both pulled the trigger saying severe weather tonight with dtx saying this:"ALL
OF THE INGREDIENTS ARE COMING TOGETHER FOR SUPERCELLULAR SEVERE
THUNDERSTORMS POTENTIALLY IMPACTING SE MICHIGAN" and GRR saying this:"IF SURFACE BASED
INSTABILITY COULD DEVELOP WITH SOME 3KM CAPE...THEN THE TOR THREAT
WOULD INCREASE QUICKLY."

I'm pretty surprised myself, considering the tornado/wind threat depends on some surface based storms, i was expecting a toned down discussion, not this.

I agree completely... It's just that I am not sure if surface-based thunderstorms CAN develop tonight across southern MI (as I mentioned in my maproom discussions about tonight). For this to occur, the boundary layer would have to remain rather deep /"well-mixed" and storms would have to root in the layer and feed off surface-based parcels. Otherwise, if this can't occur, expect elevated severe thunderstorms all across southern/central MI later tonight capable of producing large hail. If we do get surface-based tstorms, then the threat for destructive winds (60-75MPH) and a couple isolated tornadoes would be quite a threat (given we have strong sfc-based CAPE and strong 200-400m2/s2 SRH overlapping by 06z-12z ahead of the shortwave which should plow through around this timeframe) in addition to very large hailstones.

 

[Robert Dewey]

Nick, did you see the new dis. out of GRR and DTX? They both pulled the trigger saying severe weather tonight with dtx saying this:"ALL
OF THE INGREDIENTS ARE COMING TOGETHER FOR SUPERCELLULAR SEVERE
THUNDERSTORMS POTENTIALLY IMPACTING SE MICHIGAN" and GRR saying this:"IF SURFACE BASED
INSTABILITY COULD DEVELOP WITH SOME 3KM CAPE...THEN THE TOR THREAT
WOULD INCREASE QUICKLY."

I'm pretty surprised myself, considering the tornado/wind threat depends on some surface based storms, i was expecting a toned down discussion, not this.

I think this topic is more for the synoptic wind event, versus the potential outbreak of severe thunderstorms - which is discussed in the Map Room (I made the same mistake a few days ago).

Things certainly are setting up for another potentially destructive synoptic wind event... But, there are a few important differences between this system and the last system...

1) The last system put the entire DTX area in the secondary >60KNT jet maximum (polar jet?) during peak mixing
2) That system was rapidly deepening, our current system will be occluded
3) The previous system pulled a very intense pressure fall/rise couplet right over DTX
4) NAM BUFKIT had a solid 60-63KNT at the top of the mixing layer (indicates potential "gusts")

Given that, NAM BUFKIT shows mixing heights rising to nearly around 900MB a couple of hours after the frontal passage, and depending on how fast we mix out cloud cover - I could imagine it actually being closer to 850MB. That's a big difference, because 900MB shows roughly 40KNTS, while 850MB has 55-60KNTS at that timeframe. The pressure gradient is also rather steep, but not overly concerning...

I did some research and pulled up SFC and UA charts for the October 30, 2004 wind event, which featured several locations hiting 70MPH. That system also had very subtle signs of being a "big producer". In fact, DTX issued a wind advisory during the early morning AFD, and THEN upgraded to a warning after the reports of destructive winds started coming in.

October 30, 2004: http://weather.unisys.com/archive/eta_init...10/04103100.gif

Tomorrow NAM forecast: http://weather.unisys.com/eta/36h/eta_4panel_36h.gif

 

[Robert Dewey]

Pretty interesting... Latest 00Z NAM has trended stronger with the system, but still showing a solid low level jet of 45-50KNTS for much of tomorrow afternoon well into the evening. Of interest though, is the 00Z and 03Z RUC... It is quite a bit stronger than the NAM in regards to low level wind fields. The RUC has an expanding area of 60-80KNTS at 850MB which is spreading towards the Great Lakes region between 12Z-15Z, compared to the NAM which has a broken area of 50-60KNTS over the same region. I already suspected the NAM of being too strong, but the RUC did in fact initialize the SFC winds much better than the NAM - so stronger wind fields may in fact be a reality (NAM had 15-20KNTS over areas that were actually 30-40KNTS).

Since 12Z-15Z is still early, not much mixing will be occuring around the 850MB level, so it won't really translate into much at the SFC (RUC is about 5KNTS higher than the NAM at the SFC)... But, between 15Z-21Z, expect better mixing to occur and tap well into 5K FT layer (850MB). If the RUC is correct, I would expect max wind gusts of up to 65KNTS over portions of eastern WI, and possibly spreading into lower MI during the day (extrapolating the RUC). Otherwise, if the NAM plays out, then I would expect widespread 45-50KNT gusts over most of the Great Lakes (higher by the shorelines)... And 30-40KNTS if the GFS verifies.

RUC 925MB forecast, 15Z: http://www.waveformpc.com/pics/wind_overlay.gif
NAM 925MB forecast, 15Z: http://www.waveformpc.com/pics/wind_overlay_nam.gif

 

[Andy Wehrle]

Could there be another one shaping up for next week?

Out ahead of the low center, a strong moisture flow coupled with favorable upper-level dynamics is expected to lead to severe weather for parts of the southern Plains. This low is then predicted to move towards the Great Lakes and deepen. After it makes its way into Canada, strong northwesterly flow on the backside of the system could lead to gale-force winds for parts of Michigan, Wisconsin, Lake Huron, and Lake Michigan.

This sounds like a more "classic" track for a significant Witch of November-developing over the plains and lifting N/NE into the upper Midwest, rather than staying north of the US/Canadian border as today's is doing.

 

[Robert Dewey]

This sounds like a more "classic" track for a significant Witch of November-developing over the plains and lifting N/NE into the upper Midwest, rather than staying north of the US/Canadian border as today's is doing.

That's true... These recent events are probably more on par with intense Alberta Clippers... Still, it would be pretty hard to top that local wind event that occured on SUN, that was pretty wild!

Looking back though, the "Witch of November" that occured on Nov. 10, 1998 was very intense... Areas near the Mackinac Bridge experienced wind gusts of 90-100MPH (the bridge was obviously closed, LOL)... Further south towards GRR and DTX, things were more "tame" with widespread 60-70MPH gusts (Ludington, Flint, etc.).

 

[Andy Wehrle]

"The lake, it is said, never gives up her dead, when the skies of November turn gloomy..."

:shock:

Of course, the ETA has a much less impressive system, but...

CONSENSUS OF SURROUNDING OFFICES IS TO GO WITH THE GFS MODEL FOR THE WEEKEND SYSTEM...AS IT CLOSELY MATCHES THE ECMWF/UKMET AND CANADIAN SOLNS. THESE MODELS ALL SUPPORT CYCLOGENESIS OVER COLORADO AS THE UPPER TROF CROSSES THE CNTRL ROCKIES. THIS SYSTEM IS EXPECTED TO DEEPEN AS
IT LIFTS INTO SOUTHERN MN BY SATURDAY AFTERNOON.

Edit: OK, NAM/ETA has now fallen into consensus with the GFS and bombs this thing into the low 980s.

 

[Robert Dewey]

All of the medium range models are pretty intense with yet again another November Gale (this would the the third one in 15 days!)... We may have to start another thread about this one if it looks like it will hold together (it's not too far away, and most of the models agree... but I don't like forecasting wind events more than 24 hours away).

 

[Robert Dewey]

Excuse my meteorological french, but holy sh!t! Look at the 00Z NAM at 42HRS (especially the 850MB map), that thing looks like a hurricane!