Forecast/Analysis critique (02/28/05 Event)

[Todd Rittinger]

This is kinda my first serious kick at the forecasting cat and totally preliminary. I also posted it to a Canucky WX mailing list that I'm on. Any critique would be greatly appreciated! (apologies for posting this here, but I felt it doesn't warrant Target Area; Tim or Mods, please feel free to move to the Everything Else if this post violates the Weather and Chasing criteria)

TIA!
Be well, TR

Really not a forecast as I was tipped off by Kuhny, so more of an analysis and by no means complete in any way. Prior to writing this, I tried to avoid reading all list posts regarding this event. This analysis is focused on Southern Ontario.

The steps I followed:

1) Reviewed posts by Jerry on the WxCanada.com board (forecasting tips, skipping information already posted regarding this upcoming event) and Tom et al on mailing list. Additionally, followed two clues provided by Rob Kuhn: approx. event time, and inbound direction(s).
2) Head to Mike Sagers kewl model animation generator.
3) First run: 18Z, GFS-NCEP, Precip, North America, 96h. This model clearly shows 2 low pressure systems approaching SO, weaker one from the NNW, and the stronger one passing south of us from the SSW. Arrival looks like mid day Monday, with lingering effects into Wednesday. Barbs are also showing me some wind(s) attached to this event.
4) Second run: 18Z, ETA-Wisconsin, Precip, North America, 96h. This model only showed me 48h which in this case is not enough.
5) Third run: 18Z, ETA-DuPage, Precip, North America, 84h. This model agrees with the observations noted in step 3.
6) Fourth run: 18z, Canadian-Global (U of Q), Precip, North America, 144h. This model also agrees with the other two with one exception: the stronger southern low will be passing further south and east than the other models show.
7) What next? Surface (and higher) temps will effect the type of precip, and winds will determine drifting, visibility, and "piled up accumulations". Additionally, winds blowing over the lakes with affect precip totals, so one should determine great lake status for this event and direction of winds.
8) Fifth run: 18Z, GFS-NCEP, 500mb, North America, 144h. This model indicates the winds will be coming from the SSW then SSE by Monday afternoon and into Tuesday. Possible higher local accums from lake effect snow off Erie and Ontario. (I'm not sure at this point how much of these lakes are frozen over). Strongest winds appear to be Monday afternoon/evening, with the winds dropping off into Tuesday, but picking up again Tuesday aft/eve from the NNW and staying around into Thursday. 500mb temperature models are showing low enough temps that all precip should fall as snow. (see Remaining Question #1 below)
9) Then my brain exploded and I have developed a new found respect for meteorologists, forecasters, and storm chasers.

Conclusions:
While this is not even close to a complete analysis, we can draw some preliminary conclusions:
1) A winter event will occur beginning Monday, with effects felt into Wednesday (primarily drifting and blowing from strong winds, and some new precip). Monday will suck, Tuesday so-so for some of the day, Wednesday will suck. (That's official terminology as well)
2) The hardest hit areas will be (South) Eastern Ontario and the U.S East seaboard, with possibility of Maritimes. Southern Ontario itself will not feel the brunt of this event. Local accums near Erie and Ontario will be higher (assuming there is some open water). Wednesday will see local accums higher from Superior and Huron again assuming some open water.
3) Snow!
4) I have a LONG way to go in understanding the interactions between all the players in the weather drama.

Remaining questions:
1) Amount of snow based on QPF and RH.
2) Other factors contributing to, or detracting from this event.
3) Bunch of other stuff ;-)

Based on reading, reading, reading and then some reading, I'm concluding that successful forecasting relies on 4 steps:

1) Identifying events and/or event locations
2) Analyizing all the factors contributing to the event
3) Rejection or acceptance of the event based on #2
4) Refining and fine tuning as event draws closer (which could possibly lead to rejection of event)

Am I on the right track? There is so much information to consider, and as a result, I'm trying to formulate in my brain the basic steps/procedures to follow.


References:
http://www.michaelsager.com/weather/wim.html
http://ww2010.atmos.uiuc.edu/(Gl)/guides/m...sfcobs/wnd.rxml
http://jrscience.wcp.muohio.edu/coriolis/c...utermodels.html

EDIT: corrected #6 which read "passing further south and west", but should have read "passing further south and east".

 

[Todd Rittinger]

Revision One:

Lake effect snow from Mon-Wed event:
The data provided by Jill and Tom clearly answers the question about open water. I believe there is a significant amount of open water to enhance snow fall off Lake Ontario Monday, and from Superior/Huron on Tuesday/Wednesday. Now we just have to wait to see if the crystal ball is correct, or I just take it bowling...

 

[Robert Dewey]

This is a very interesting situation indeed. Models are pretty much all over the place in respects to where the SFC low will actual setup. As of right now, anyone from eastern lower MI to New England is game for some big accumulations. You are right about lake enhancement as well - For instance, northern lower MI (APX) states that snowfall amounts could be very impressive, into the double digit's (inches/accumulation).

Both the NAM and GFS seem to agree that this will be an extended event - Possibly 24 hours - With high snow to liquid ratios. What I get from the current models, is large swath of MDT to occasionally HVY snows persisting for 18-24 hours. Mixing ratios aren't really that impressive, only on the order of 2g/kg, but with the air as cold as the models are showing that is most likely why. Cross sections show relative humidity of >80% all the way through 500mb, with vertical velocities between 4-8 -ub/s well into the -15C to -20C layer - which is best for snow growth. There is actually some convective instability present in beneath the 700MB layer on the theta-e fields, along the TROWAL, which could make things even more interesting, but I would really like to see this extend just a tad higher, with stronger vertical velocities.

Plenty can go wrong between now and then, as is usual with systems containing the potential for nor'easter cyclogenesis. I could also imagine this storm moving up the east coast, with little or no reflection west of the Appalacians...

 

[Todd Rittinger]

Here is another statement in regards to this system:

AN UPPER TROUGH IS ADVERTIZED TO BECOME NEGATIVELY TILTED AND EVOLVE INTO A CUT-OFF LOW RIGHT OVER SOUTHERN ONTARIO. THE 700 AND 850 MB LOWS ARE ALSO PROGGED TO SLOWLY DRIFT OVERHEAD ENHANCING THE LIFT AND MAINTAINING A SLOWLY ROTATING SHARP INVERTED TROUGH/LOW OVER THE AREA.

What the hell does that mean?

Be well, TR

EDIT: OK, kinda got it at the links below. Man, how do you guys do it? :? Damned if I'm gonna give up though...

http://www.theweatherprediction.com/habyhints/126/
http://www.theweatherprediction.com/habyhints/127/
http://www.theweatherprediction.com/habyhints/128/

 

[Robert Dewey]

Originally posted by Todd Rittinger
Here is another statement in regards to this system:

AN UPPER TROUGH IS ADVERTIZED TO BECOME NEGATIVELY TILTED AND EVOLVE INTO A CUT-OFF LOW RIGHT OVER SOUTHERN ONTARIO. THE 700 AND 850 MB LOWS ARE ALSO PROGGED TO SLOWLY DRIFT OVERHEAD ENHANCING THE LIFT AND MAINTAINING A SLOWLY ROTATING SHARP INVERTED TROUGH/LOW OVER THE AREA.

What the hell does that mean?

Be well, TR

First, negatively tilted means the trough will be elongated in a northwest to southeast fashion (rather than the usual northeast to southwest). An upper level cutoff low means that the system is not located within the jet stream, and may hang around for awhile, as opposed to being stuck in the jet stream, where it would just scoot along. The 850/700MB lows being overhead would enhance lift, and provided enough moisture is present, create precipitation. That's because with the circulation overhead, the air will rise (lift).

Still very interesting, and I try not to get my hopes up because these northeast systems are *very* tricky...

 

[Todd Rittinger]

Very clear Robert, thanx!

P.S. from your post and my reading, I take it that from a severe weather point of view, this is a good thing?

Be well, TR

 

[Robert Dewey]

Originally posted by Todd Rittinger
... P.S. from your post and my reading, I take it that from a severe weather point of view, this is a good thing?

Be well, TR

It depends. Generally, the area directly beneath the 850/700 tend to be cloudy/cool, which would limit instability in the spring/summer. But, areas very near the low and mid level low pressure centers tend to get those unpredicted "mini supercell" outbreaks, or so I have observed. The negative tilt would be good in a severe thunderstorm setup, especially if you can get a slightly negatively tilted 850MB trough, while maintaining a relativly zonal flow aloft (to increase 0-6KM rotation)...

I doubt we will see any severe thunderstorms though, obviously :lol:

 

[Joel Wright]

A tenth of an inch of light rain, changing to light snow with maybe a half inch for northwest IL. I'm so pumped up for this storm, I just can't wait.. :roll: