Bizarre storm…no doubt…the title of the blog this afternoon will serve as an analysis of what happened and why the forecasts were poor for the end result. although as I’m writing this it’s actually finally snowing pretty good…but again even with this band that will last for awhile…we still won’t get up to our forecasted totals…so let’s analyze why as I do a postmortem on the storm.
I/WE WERE WRONG….so let’s get that out of the way. I need to refer to previous blogs however to point out certain things…NOT in an effort to say…see I told you this could happen…but more for the purpose of referring back to them for additional explanations. Please look back to THU/FRI’s blogs for that information.
OK now let’s get into the why factor…
Twice per day the NWS sends up balloons (6AM/6PM) called soundings that go up through the atmosphere and collect weather information in the form of temperatures/dewpoints/wind direction/speeds. From that information we get a profile of the atmosphere. We’ve talked about this extensively in the past.
The balloon this AM that went up at 6AM at it shows exactly why we had a sleet storm and not a snow storm that was expected. Look at the diagram below and click on it to make it larger.
I want you to pay attention to several lines…one is the diagonal BLUE line that I put in that goes from the left middle of the image up to the right towards the 32F. That represents the freezing line. As the balloon goes up…it traces the temperatures as it ascends…that is represented by the RED line. It also sends back dewpoint information represented by the GREEN line. Where the RED/GREEN line overlap that means the air is totally saturated. The more they spread apart the drier the air is. Notice where the RED/GREEN lines intersect then go to the RIGHT of the diagonal BLUE line. That means that the temperature and the dewpoint both exceeded 0°C or 32°F…in other words…above freezing.
What does that mean…well snowflakes that formed dropped through that layer of above freezing air. What happened? They melted…turned back to liquid…then dropped through the layer of air that was WELL below 32° down towards the ground. What happened then? They re-froze into pellets/sleet and boom there goes the forecast.
It poured down sleet…and we easily lost 4-6″ of snow from that. Sleet doesn’t accumulate nearly as fast as snow does. It would take hours and hours and hours of pouring sleet to accumulate 6″…never has happened before in KC. Whereas it would’ve taken about 3-5″ of heavy snow to accumulate 6″ of fluffy powdery snow. That obviously didn’t happen.
To show just how close this was to what we thought…now let’s analyze just how thick that “warm” (above freezing air was).
To do that let’s use the information from NEXLAB…take a look at this data.
This is more detailed data about the balloon’s information as it went up in the atmosphere…for the sake of discussion the #’s on the far left will be called “levels”…the information from the levels are categorized but the top line…remember everything is metric.
So for example…at the SFC (surface) which has an elevation of 270 meters the temperature as the balloon launched was -15.9°C with a dewpoint of -19.5C. Convert that to English units and at the surface with an elevation of 886′ the temperature was 3° and the dewpoint was -3°. Following me?
Now let’s go up through the atmosphere and we find that through “level” 13 the air is totally below 0°C or 32°F. Good so far…oh and to determine how “thick” that layer of cold air is…subtract the level 13 height…1844 m from the surface height/elevation 270 m. You get 1574 m or 5164′. So what this means is that the layer of cold air extends from the surface to 5164 feet. OK?
Now let’s look at the trouble area. Look at level 14/15/16. Those layers are 0°C+/32°F+ and do the calculation. Level 14 was at 1973m-270m=5587 feet above the ground. Level 16 was at 2439m-270m=7116 feet above the ground. 7116′-5587′ = 1529 feet.
1529 FEET…that is the layer of “warm” (32°F+) that destroyed the forecast more or less. 3/10’s of a mile…and to add insult to injury as far as the forecast goes…that layer of air reached a whooping 1°C…or 34°F. It was 2° above freezing. 2°.
Now where did the models go wrong…they were forecasting this layer to be there at the beginning of the event and then erode away as the evening wore on…hence the forecast of sleet to snow and the model trends were for the atmosphere to be colder and colder so that the “warm” layer would be an almost non-factor. As a matter of fact here was the forecast profile of the atmosphere for 12AM this morning from the 6AM yesterday morning model run…this is what led me to thinking we could get 6-12″ in places.
How could we have done better? That is the tricky part. One would be IF we had access to temperature data every hour on the hour that was true data…i.e. balloons that went up every hour for real-time information. That is not going to happen. On occasion aircraft will help out with temperature reports…not sure IF that was available for the event last night. Somehow we needed to figure out (and really after about 1-2 hours of sleet I knew we were toast) when this layer of air would disappear or even IF it would…it didn’t till this afternoon. The other thing about this is something that I wrote about the other day. We have dozens of temperature sensors on the ground through the region that give us information every few minutes or more frequently than that faster than that..and yet rely on about 100 sensors/balloons for the temperatures of the atmosphere aloft for the country as a whole…although satellites are helping to fill the data voids a bit now…at least where skies are clear. Not exactly helpful when there is a storm and clouds in the area of interest.
So we erred in two major ways…one was trusting the models were correct in the elimination of this warm layer of air aloft before the event really started…and two was the assumption the models were sort of correct with the amount of precipitation they were generating…remember that map I posted yesterday evening…showing parts of the area with over 1″ of liquid. I knew that was wrong…so I cut it by about 25-50%…then factored in the higher and fluffier ratios…and still came up with the heavier snow totals. You’ll notice the snow band this afternoon is set-up where the heaviest snow was predicted. This would’ve/should’ve been the icing on the cake for the snow totals forecasted by yours truly.
1529 feet and 2°….Geez
All this with a surface temperature below 5°. Never seen that before in this part of the country. It may have happened somewhere in the Plains…but I sure don’t remember writing about something like this before
Latest radar trends are getting interesting again as we’re not done yet with the storm and there is certainly the potential for additional snow accumulations from KC southwards down 69/169 and I-49 into S MO over the next 6-8 hours or so. Snow is increasing across parts of central KS now. Heavy snow is falling in Hutchison and Pratt and is moving towards the ENE. We still need to erode the above freezing air that was on the Topeka sounding this AM around 5500′ however…once that is done we can actually get some efficient accumulating snow to fall.
The best odds of this happening are from KC southwards…and KC will be on the northern edge so it will make it tough to figure out…and we’ll just have to watch radar this AM. For the next few hours keep an eye on radar information from the NWS in Topeka, KS…and you can track the sleet/snow moving towards the ENE.
The activity as of 10AM west of Emporia is most interesting to me in terms of how it plays into things this afternoon. additional accumulations of 1-4″ are possible from KC southwards should this play out.
Reports from around KC indicate anywhere from 1/2″-2″ of a mostly sleet and snow mixture. areas across N MO and NE of the KC area have had 2-4″ thus far and will miss out on the last batch of precip moving into the region.
Areas south of KC have had mainly sleet and even some freezing mist/rain. accums have been minor but there are slick conditions on the roads.
Keep and eye on the radar above…then this afternoon look at the radar below. I’ll update the blog again around 2PM or so. For snow lovers it’s been frustrating and while we may get some additional snow in the metro…this will go down as a forecast bust for me/us. I’ll explain more about the why of the forecast bust this afternoon.
I’m sure some want to rip away at me/us. Human nature. Totally get it…and I can’t be doing blogs saying the forecast worked out…and then not admitting when the forecast didn’t work out. Nor will I play the revisionist history game and say well 3 days ago I said this…so I’m right in the end. I don’t play the game that way and my readers know it. I’m publicly critical of my forecasts to a fault, moreso than any TV meteorologist I know, and this forecast, clearly didn’t play out according to plan.
So have at it…I’m a big boy.
More this afternoon
In the end…as radar echoes are decreasing the sleet has won the fight for now..although to be honest with you…even IF this would’ve been all snow…it’s hard to imagine it would’ve been over 4-5″ in just a few hours time.
Most areas have had 1-2″ of sleet and snow…some may have done a bit better in the snow department…perhaps 2-4″ on the far northside of the metro through N MO.
As near as I can tell the devil to the sleet was what was happening up around 10,000 feet up where the temperatures in the clouds were only near 30°. This is not exactly a prime temperature to get snowflakes to form. Usually like to see that 10-15° colder. Meanwhile the temperature profile of the air below that was in great shape for a high snow ratio event (lots of fast accumulating fluff). When the temperature profile is like it is you get lots of chunks and not as many flakes. On occasion as the mid part of the atmosphere cools in spots you will get flakes of snow for a period of time…
It’s amazing to think about but the temperatures at 1AM are 4°…and yet aloft the temperatures are about 25° warmer right now. Odds favor today to be the coldest March day ever in KC…as temperatures may stay in the single digits all day long. So we’re in rarefied territory right now in terms of the weather.
Here is a graphic my colleagues at the NWS in Pleasant Hill put together…
As far as what’s going on out there now…here is a look at radar from the NWS in Pleasant Hill
So let’s move on to the potential of additional snows as the disturbance in question moves our way. The actual “storm” part of this is still aways away and it’s not out of the question as it gets closer this afternoon that we cloud see renewed snow to forma and move towards us. Tough to imagine however we can get more than 1-4″ of snow out of that potential however IMHO.
The main part of the storm is, as of this writing, in AZ now and moving ENE. It’s forecast to pass well south if the KC area. As it does so this afternoon we may see some additional snow develop across KS and spread towards the ENE. This would be our chance of picking up an additional 1-4″ should this pan out. Certainly not a slam dunk though…but let’s not throw in the towel yet on the storm and the snow aspect.
Just for the heck of it I’ve created another snow map for you…let’s see how it pans out…the only way we get to 6″ I think in the KC Metro is if we get a good chunk of snow as the day moves along…we’ll see about that.
I’ll update you again on the news…may try to get another hour of sleep before going to work.