Wednesday, July 28, 2010

Tornadic Supercells are on the menu for July 29th

Well I'm currently in Winnipeg for the next few days before I head out to the Lake of the Woods for the long weekend. Fortunately it looks like mother nature may unleash a mini outbreak of severe weather confined to parts of SE Saskatchewan and SW Manitoba tomorrow during the late afternoon.

A weak low is forecast to develop in the afternoon and situate itself somewhere near the Moosomin-Virden area. A warm front looks to be draped from NW-SE toward the international border. Moisture looks to pool along this front with dews likely in the low 20's. Great crossover winds are forecast to phase with the highest instability which should allow for storms to rotate with ease. The show looks like it'll start in the late afternoon. (6 o'clock magic)

Limiting factors for tomorrow: well it ain't moisture...the only thing I can see is capping in the area. H75 temps aren't that high, and the H85 thermal ridge looks to move east during peak heating to allow the cap to be breached! At the H50 level... it also looks like a weak shortwave will traverse the top of the ridge and some cooling moving in may lower the heights enough to again allow for storms to develop...timing of all these features may push back development to 7pm or 8pm...but since it's summer the days are still quite long.

Anyways...I'm quite excited for tomorrow...looks like Carlyle in 2008 and Pipestone in 2007 if the warm front can develop like it's forecast to do and a storm can ride the frontal boundary...CAPES looks insane too...~2500-3500 j/kg...and if you incorporate some ET into the equation CAPES might hit 4000+ j/kg! Here's to hoping!

Dave...what do you think?

Tuesday, July 27, 2010

Recap of July 26, 2010

All the ingredients were there, although the low-level shear was a little on the weak side. We targeted Carman, MB.

On the way to Carman we saw a storm try to go up west of us, but it really struggled against the cap and it was really neat to see the storm die from the bottom up.

We got to Carman and ate, got into the car and waited.

And waited and waited and waited.

An area of persistent cumuli was just west of us, not really moving. This had to be the place.

And waited and waited and waited.

The towers got more vigourous as we waited there, sometimes sending up more serious pulses:

But they didn't last long, as they were pretty thin and were obviously not breaking the cap. There was, however, one persistent tower that was much wider at its base:

Then it happened. The cap broke. I was telling the PASPC what I was seeing and, while I was on the phone with them, a new RADAR scan came in and confirmed what I was seeing: the storm was becoming severe.

It looked like a multicell line for a while, so we knew that it would require a bit of time to become organized. So we decided to go ... uh ... in search of frozen precipitation. (I know, don't do that.)

We got some twoonie-sized hail near Oakville, drove to Elie and bombed south through some quarter-sized hail. We came out the other side to see a pretty nice wall cloud. If it was rotating at all it wasn't very quick rotation. A scud tag out the bottom of it may have fooled some people into thinking that it was a funnel and, indeed, one was reported. (Not by us.) This picture is taken after the scud tag dissipated:

The storm had taken a hard right turn and so we had to stay ahead of it. Unfortunately, the road network there is conducive to going pretty much any direction except southeast. But we did happen to make it southeast of the storm, but not before going through some golf ball to baseball hail. I was scared, at least a little bit, that I would lose a windshield, but there weren't too many of them.

Once we got there, though, it was clear that it wasn't going to produce. We stayed back and got some nice pictures:

By the way, I will have the RADAR and satellite pictures from this event on Weather Central hopefully soon, like within a week. The lead meteorologist said he didn't issue a tornado warning for it only because he knew we were on the storm. Having looked at the RADAR I can understand.

Wednesday, July 21, 2010

Severe Threats for Edmonton Area on Thursday & Saturday with something potentially big for next Saturday the 31st

Well not much has been happening on the severe weather front this past week. Friday of last week was the last major severe weather day with tornado watches/warnings being issued for areas near Bassano and Brooks, Alberta.

Things will finally change for Thursday as a weak low sets up tomorrow near the capital region. The low level winds are going to increase to around 30km/hr out of the southeast...that's it for speed shear. High CAPE values, low level moisture, and amazing directional shear combined with a surface trough are all we have. We have no flow aloft to effectively vent the updraft...hopefully that can change...if that does then something big will happen.

However when facing reality it is likely after viewing water vapor imagery that the strongest mid-upper level winds will reside south/near the international border by tomorrow afternoon. So this means that we'll be dealing with strong multi-cell storms with left splits and right splits. Colliding outflow boundaries will occur I can guarantee that. Any storm that can find a boundary may allow for a brief tornado if moisture does make it into the upper teens like it's supposed to based on the 00z NAM/GFS.

Saturday looks interesting over Northern/Central Alberta too...the ridge breaks down allowing for a linear type convective line to develop after 6pm from around Fort Chipeywan through Edmonton to about Red Deer. Ingredients are in place for a squall line to rip through bringing an end to the warm, relatively humid weather for a couple of days...this wiper blade will flush out any moisture currently pooling in Alberta...after that it looks like a lull in severe weather chances for some time (2-3 days at least)

But Saturday...despite showing a strong squall line signal...might host an opportunity for discrete supercells...there is way better speed/directional shear associated with the low-upper level jets and when combined with a strong short wave moving looks like it might actually phase with the higher capes and moisture from 6-9pm...

And finally...about next Saturday the 31st of July...yesterday's run showed it better then today's but it looks like a strong upper low will move on shore and dig which will work to amplify a ridge over eastern Alberta through Saskatchewan. A great mid level SW flow develops over southern and central Alberta...I won't say anymore since that day is several days out...but that time of the year is quite sensitive to Capital city residents.

In the mean's to hoping for a great Thursday and Saturday!

Maybe someone will actually consider chasing these events especially on Saturday and actually 'chase' like they say they will instead of missing one of the few big days that Alberta has to offer in terms of severe know who you are...starts with an A and ends with lysa!

Saturday, July 17, 2010

Updates galore

Okay so it has been a pretty busy set of days. July 13th was pretty good in that 8 of us went out and we caught a striated supercell that teased us for about 5 hours. No tornadoes, but the structure was impressive.

We went back to Winnipeg and Wxdog picked me up in the morning for our chase vacation, which we're on now. We targeted near Minneapolis and had to get there in a hurry.

Not fast enough, it turned out. Storms blew up a bit on the early side and lined out after about half an hour. It was a long, frustrating day.

Wxdog and I then started off in Omaha, NE, with our initial target being somewhere around Akron, CO. We liked the dewpoints into the 60s in the area and although the 500 mb flow was meager, we thought with some okay 850 winds opposing them that we might get Wxdog a birthday surprise.

During the drive the RADAR showed us a mesoscale rotation area southwest of Akron, and convergence looked to be at a maximum just east thereof, a sign that our initial target was going to be close to working out.

We got to Ogallala, NE and saw the cumuli bubbling up to our south and southwest, which was corroborated by the visible satellite imagery: initiation was there. Driving to Akron we saw 3 distinct storms--one off to the southwest south of Denver, as well as a pair of okay-looking storms to our south and southeast. We decided, based on RADAR-observed storm motion, to go south and try to a) see both storms from behind and b) perhaps drive in between them. We got almost straight east of the dividing line between the two storms. On the way between them we saw some beautiful midlevel funnels that never came close to threatening the ground.

When we got to the front side of the storms we booked south to see what they looked like and what we saw was pretty cool: the north storm had a feature on it that looked like an epic struggle between becoming shelfy and wall-y. Some close lightning told us to leave the area so we went south, eventually getting onto the now-dominant south storm.

Some repositioning later we found ourselves south of the now south-moving storm that had some weak rotation in it, but visually and on RADAR it looked outflow-dominant. We kept with it for a while but, realizing we were getting into an area of weaker and weaker upper winds, decided to leave the storm.

Which, of course, is when it decided to look like a supercell on RADAR. A hook emerged out of the mess and we were just southeast of it: almost perfect position. We repositioned ourselves to be just east of the hook so we could see the inflow region, and we were treated to a gorgeous HP supercell beast with moderate rotation in it. It was moving south at quite a clip now, so we had to take our pictures and get out of there. It looked okay for about half an hour then became outflow-dominant again. We stood by the side of the road wondering what to do when we saw another inflow feature develop to our northwest. The outflow had collapsed and left us with another chance--and RADAR confirmed this soon enough.

Long story short, another beautiful stacked-plates laminar flow HP supercell emerged and we were in perfect position to see the beaver's tail, the storm-scale rotation and more significant low-level rotation. At one point it put down a cone funnel that went about halfway to the ground, but this was about the best it could do.

It soon became outflow-dominant and, as it was getting pretty late and pretty dark, we gave up for the day, and that's when the storm really lined out and finished the day for us. A medium-length drive to Goodland, KS and a stop for dinner with CoD ensued, and we went to our hotel for the night. Wxdog was happy with his birthday storms.

Yesterday was a repositioning day with marginal chance. We hung on as long as we could near Imperial, NE, but it didn't go.

Now for today. We're currently driving north from Sioux City, IA to somewhere around Fargo. Let's go over that list again.

Moisture: plentiful. Surface dewpoints in the area are already in the mid to upper 60s F and should reach 70 with ET and advection.

Instability: awesome. Because of the moisture and steep midelevel lapse rates observed on upstream soundings (BIS, ABR) there will be no shortage of instability.

Lift: great. In fact take your pick. Surface low, warm front, cold front. I like the low itself near the warm front. Either way, plenty.

Shear: very good. 50 knots is coming in aloft and the low-level winds should really crank up this afternoon with the approach of the upper flow.

In short, it looks like a promising day. The only negative I can think of is too much forcing, which could cause the storms to go linear in a hurry. Because of the proximity of the surface low, I don't think that's as likely to happen today as it was a couple of days ago in Minnesota. Backed winds near the front should help to keep storms discrete loner. But watch out, southern Minnesota: you'll likely get a major wind damage event this evening and/or tonight.

Follow us along if you like. We call ourselves "Winnipeg chasers".

Monday, July 12, 2010

Monday July 12, 2010 wrapup and a look ahead

So Justin went out today and I didn't.

In 3 words: too much forcing.
There were a lot of storms out there today and perhaps one produced, but finding that needle in the haystack would have been nigh on impossible.

I was nowcasting for him and I knew it was trouble when storms went off at about 2 PM MDT. A brief tornado was reported in the post-frontal air near Calgary. (I'll believe it if I see pictures more convincing than those currently on TWN's site. What I see there is a scud bomb. Nothing more.) Anyhow, storms went all over the freaking place, and because the upper flow lagged the surface forcing they were all multicell garbage. Justin was in the best area thermodynamically but the storms just couldn't lay down and stop competing with one another.

Tomorrow is a chase day that a few of us are going to take in. The current target looks to be Fargo to Grand Forks.

Moisture should be pooling in the RRV with surface dews approaching 20°C. This won't be a shallow moisture pool either, as good 850 mb winds will advect in moisture from the south.

Instability, as a result, should be fine. MLCAPEs 1500 to 2000 J/kg look reasonable.

Shear won't be a problem like it was today. At 500 mb 40 knots will be there at least. As for turning profiles we'll be good there, as the 850 mb winds look to be around 30 knots.

Lift will also likely be not a problem, be it with a pre-frontal trough or with one of the fronts.

So here's a forecast sounding for around Fargo at 00Z tomorrow. Would you go? I would. Will. Whatever.

Sunday, July 11, 2010

Monday: to go or not to go

There is a chance of some really good storms tomorrow near the Battlefords. Justin posted about this before, and here are my thoughts.

Moisture - progged to have dews in the upper teens at the surface.
Instability - MLCAPEs around 2000 J/kg.
Lift - warm front in the area draped across the South Saskatchewan River valley.
Shear - Good turning with height especially near the warm front, but more robust 500 mb flow is forecast to the south, down by Leader and area.

I'm a little bit skeptical of the moisture, seeing as how dews are currently in the 10 degree range--and that's at the moist stations.
Shear is only okay because the juxtaposition of the jets isn't great, but with looping hodographs a few supercells aren't out of the question.

I keep vacillating on whether or not to go, because it's a long drive for a one-day wonder. The moisture is the part that concerns me the most, so I'll be watching the dewpoints throughout today and tonight, and if they come up enough (and stay up) I could be making the long trek tomorrow.

If it all comes together, supercells will be likely along the warm front. Because of the more looping hodographs and less upper support, wet HP-ish rather than classic supercells will be the order of the day. Then again, maybe that would work in my favour because of raining near the updraft and providing the moisture in situ that's not there at all now.

If the moisture is indeed there, tornadoes are likely. If not, then because of the dry subcloud layer, wind will be the order of the day.

Saturday, July 10, 2010

Update for today

Wow, have things fallen apart for today!
This morning a cloud canopy is just to our north:

The surface winds are veered:

And the moisture isn't all that good:

I doubt there'll be any chasing to do over southern Manitoba this afternoon. I'll still be on the lookout, but storms will likely be embedded and kind of crappy.

Ah well, there'll always be more storms!

Active Few Days on Tap for the Prairies starting Sunday

Well it looks like a big bad upper low will be showing its face over the Western Prairies starting on Sunday.

This setup should yield some strong-severe thunderstorms along the foothills on Sunday which will pave the way for a better setup on Monday over West-Central Saskatchewan as the Upper Low edges slightly Eastward. A moist & healthy H85 jet gets going early Monday as the mid-level flow crosses over from the WSW at a decent clip. This should allow for great speed/directional shear with height. Now tie that in with high temps/dews at the surface and some cold air aloft and we my friends have an atmospheric profile with steep lapse rates conducive to supercells with large hail and possible tornadoes when you factor in the forecast shear profiles.

The tornado threaticus looks to be maximized along a Battleford - Saskatoon - Outlook Line along a warm front/surface trough that looks to be situated in that area around 4pm on Monday.

I've already heard that a certain someone may be making the drive from Winnipeg if this setup pans out the way the 00z NAM run suggests. Tuesday could be interesting too with the focus shifting slightly eastward towards the Regina - Yorkton - Estevan area.

Either way this setup bears watching since we might be in for 3 severe weather days...with the latter two days having heightened chances for tornadoes.

Ahh, this second night shift is killing me...I need some sleep!

Over and Out!!!

Wednesday, July 7, 2010

Saturday July 10, 2010: northwest flow outbreak?

Some of the more neglected setups in our neck of the woods are northwest flow setups.
Too bad, as these can be pretty good: for instance, Gretna 2003.

Okay, so let's look at the 08/00Z NAM run valid 11/00Z.

Moisture: well, as I write this we're in a pretty stagnant airmass with a northwest flow and still our dewpoint is a solid 14 degrees. So this time of year, one day worth of advection and unmitigated evapotranspiration can get dewpoints up into the low 20s. And this is what's forecast.

Instability, therefore, shouldn't be a problem. And the NAM is forecasting really healthy MLCAPEs in the area, around 2000 J/kg.

Shear isn't a problem. In fact, shear looks wicked:

Lift? Well, we won't really know till then. Models are notoriously bad at this time range anyhow, especially with subtle lifting features. But for what it's worth, the NAM paints this as lagging and therefore being a negative in the mix.

And because of this, the forecast RADAR image looks dry in the MB/ND/MN border region.

So we add this all together and we get a prog sounding and a prog hodograph that look like this:

Quite impressive, eh? I will definitely be chasing Saturday--heck, a local chase like this is a must-see.

Thursday, July 1, 2010

Southern Manitoba Canada Day chase?

I'm sitting here at home and watching things bubble up just to the southwest of Winnipeg.

At 19Z satellite imagery indicates a field of congested cumuli near the Manitoba escarpment. Check it out:

Upper charts and local VADs depict a decent amount of flow and there are many wiggles in the water vapour imagery. The SPC mesoanalyses show in excess of 1500 J/kg of MLCAPE.

Surface winds are veered a little bit but are pretty weak right now.

So if we can get an upper impulse coming in to increase lift and back the low-level winds, magic could happen.

I'll be on the lookout to go chasing this afternoon.