A look at the weather

Posted by RC on Feb. 22, 2016, 10:51 p.m.

As some or most of you already know, I'm very much interested in the weather and meteorology… at least sometimes. I tend to lose interest in a lot of things after a while and meteorology is no exception, though I always come back to it anyway. Since my area is supposed to be getting a decent winter storm in the coming days, I thought I'd give you guys a glimpse at what I like to do when such events arise.

A brief look at the impending storm

See this Texas booger butt that's within that big, red circle? This is what's heading my way for the "big" winter storm of 2016. Note that I live in Indiana and the arrow is tracked to Ohio - there's a reason for this and that reason is because it's not going to directly hit my area, but that doesn't mean I won't be getting any precipitation. It's a big system, after all.

The system is to arrive in the area in about 30/36 hours which puts us into Wednesday. Of course, the track and timing is still uncertain as the weather is unpredictable despite our best efforts at predicting it. It's a guessing game, really - a guessing game in which patterns and history play a massively major role.

Looking at this radar image alone isn't enough to determine anything, really, so this is where other data comes into play.

Atmospheric soundings and models

I might not actually be a meteorologist, but that doesn't stop me from making my own forecasts. Atmospheric soundings and various forecast models help me when trying to predict what's going to happen in my area. I get area specific data, analyze it, and try to determine what the future will bring in terms of weather related happenings.

Let's take a look at a Skew-T for Wednesday afternoon:

I never really use Skew-Ts much when forecasting winter weather as the software I use (Bufkit) to analyze atmospheric data has a handy dandy overview section which provides all the data I need. Still, Skew-Ts are an important part of forecasting the weather, so it's nice to take a look at it anyway.

This Skew-T is for 18Z on Wednesday. Z time is pretty much the same as UTC or GMT, so for my time this is 1PM on Wednesday. The green line on the Skew-T represents the dew point whereas the red line represents the temperature. The higher up on the graph the lines go, the higher up into the atmosphere the readings are for with the lowest points being the surface readings.

The green and red lines are pretty tightly bound together - this means that the air is saturated with moisture which in turn means that there is most definitely going to be some precipitation going on. We can tell what kind of precipitation it will be based on the temperatures.

On this Skew-T you can also see the colorful numbers and barbs on the right-hand side; these represent the wind in knots (I think). If you convert this to MPH, you can see that the winds are going to be around 40MPH. This is going to make for a very windy, snowy day on Wednesday.

A look at the real toy: the overview

This is probably my most used tool when it comes to forecasting the weather. It does pretty much everything I would have to do myself when it comes to reading the Skew-T for forecasting the weather, so hurray for shortcuts!

Basically, what you're looking at here is a heap of different types of formulated data overlaid atop one another. The colorful, blocky looking greens and purples represent the relative humidity, whereas the red numbers and circles represent the omega values. The pink and yellow lines represent the ideal area within the atmosphere in which dendrites (snow flakes) would form - this is the area between -12C and -18C. The white line represents the amount of snow accumulation based on the given snow-to-liquid ratio.

I can't really go into too much detail because I can't remember every single thing about what all of this actually means, but I'll try my best to explain what's going on here.

Negative omega indicates vertical lift within the atmosphere - this is needed for snow to happen and probably some other things I'm not thinking about at the moment. The lower the omega value, the heavier the snow could possibly be. The negative omega, however, needs to be within an area of high relative humidity and within the ideal area for dendrite growth.

I'm not sure if you can tell through that picture or not, but we've got values of omega at -26 within a 95% relative humidity zone - the only thing is that it's not really within the snow growth area. The higher numbers are, such as -8, though, so not all hope is lost for heavy snowfall.

Now onto the more interesting bits

Now that you hopefully know a tiny bit about what the crap I'm about to talk about, it's time to move onto the point where I'm going to forecast the snow accumulation for the Wednesday/Thursday event.

We know it's going to snow. We know the storm is coming from Texas. We've got the latest data from the NOAA for my area which shows that it's going to be a somewhat heavy snow as well as pretty windy outside. How do we determine the amount of snow accumulation that I'm going to get from this system?

It's not really as simple as opening up Bufkit and checking out the overview, though it also is in a way. Bufkit does a lot of things so I don't have to, but I still have to figure out what the snow-to-liquid ratio is going to be.

Before I get too deep into this, I should probably explain a little bit about the snow-to-liquid ratio. The average snow-to-liquid ratio is 10:1, which means that for every 10 inches of snow is the equivalent of 1 inch of liquid precipitation. A colder snow won't be contain as much liquid as a warmer snow would, so colder snows would have a higher snow-to-liquid ratio than a warmer snow would. Snow with higher ratios are more powdery and not really good for making snowmen whereas snows with lower ratios are more wet and great for making snowmen.

Earlier tonight using older data, I decided to go with the method which uses the maximum temperature within the sounding profile. By doing this, I came up with a 5:1 snow-to-liquid ratio which brought the accumulation estimate to 3 to 4 inches of snow for my area, but this was considerably lower than what the local media was saying - it was, however, right on target for what the National Weather Service was saying. I trusted the data and my assumption on the 5:1 ratio and went ahead and posted it to my Facebook page for my local area weather.

Now that I've got the new data in, though, the amounts are a bit different. When using the initial 5:1 ratio, we're getting about 5 inches of accumulation in the area. What I actually neglected to do originally is use historical data based on the system's track to determine a better and most likely more accurate ratio for the storm.

This system originated in the Colorado area before moving into Texas. Based on this information alone, I can determine through historical patterns that this system's snow-to-liquid ratio will likely be 7:1 or 8:1; Colorado systems typically yield a ratio of 8:1, though systems originating in the Gulf of Mexico typically are around 6:1. Since the storm is going through Texas and close to the Gulf, assuming a ratio of 7:1 should be okay.

This system - using a 7:1 ratio - will bring snow accumulations of between 7 and 8 inches to my area. This is a big difference from my original 3 to 4 inch estimate. Had I used this ratio on the old data, my estimate probably would been about 5 inches. Still not the same, but not as off as it's portrayed in the currently available data.

This is all subject to change as more data comes in, of course. Nothing's ever certain this far from the actually event, and even then you can't be 100% certain about what's going to happen. It's all a guessing game - a fun guessing game, nevertheless, but a guessing game.

Something something end of blog bit

I hope that you found this at least somewhat interesting. I know I didn't really go too in-depth with things and a lot of it probably made no sense, but I just felt like giving you a peek at what goes on when I try to forecast snowfall. It's different for thunderstorms and whatnot, though snow is more fun in my opinion because you have to guess how much snow you'll get instead of just checking if the conditions are right for thunderstorm development.

I might update this blog if you guys are interested in seeing how the storm pans out and if my predictions are right. This 7-8 inch estimate is more in line with what the local media is saying, but I'm honestly still not 100% convinced that we'll get as much snow as it's looking like now. Maybe it's just because I'd hate to see my initial estimate get burned.


RC 8 years, 1 month ago

It had to happen. You had to be miserable.

Anyway, I guess I'll make my final assessment of the night. I've got work in the morning and I probably won't be around until the system's completely out of here, so I'll be able to at least write up a conclusion or something to this little storm tracker blog.

The snow has pretty much tapered off for the most part with maybe some light snow still falling. We've only gotten about 2 5/8 inches of snow depth the last I checked. It was difficult to check on the accumulation as it was melting as it reached the surface due to surface temperatures being above freezing all day long.

I read on a forum that the National Weather Service in Northern Indiana had measured almost 3 quarters of an inch of liquid out of a little over 4 inches of snow, bringing the snow-to-liquid ratio to 6:1 - slightly lower than I imagined with the system coming from Colorado, but a little bit more than my original 5:1 that I had been using a few days ago.

Anyway, the latest NAM and GFS models are showing an additional inch of accumulation tonight at the 6:1 ratio, but if it gets colder overnight that ratio could get a little bit bigger… either way, based on these two models alone, I'm thinking less than 2 inches of additional accumulation will occur through tonight and into Thursday.

The National Weather Service did finally adjust the Winter Storm Warning they have issued for me. They're now expecting 2 to 4 inches of additional accumulation instead of the original 8 to 12 (2 to 4 additional would mean 4 to 6 inches total accumulation for me).

I've got no time to post any graphics or anything tonight as I need to get up in about 7 hours and therefore should sleep, so I'm just going to end this post short for now. I'll see what's going on in the morning and hope that I can make it to work, and then after I get home and the storm's over I'll see what all went down.

I'm pretty confident in my original 3 to 4 inch accumulation prediction, now… or 2 to 4 inches as that was the last prediction I posted on facebook. I wasn't really buying the 4 to 7 inch accumulation prediction I posted above so I didn't post it to my facebook page, but I guess technically that was my final prediction. Still might come true if we get 2 more inches of snow, though I'm hoping we don't.

Seleney 8 years, 1 month ago

till might come true if we get 2 more inches of snow, though I'm hoping we don't.

Hey, if you don't want it. Give it back. I want snow!

Omega_Squid 8 years, 1 month ago

Quote: RC Trout Weather Lord

It had to happen. You had to be miserable.


RC 8 years, 1 month ago

Quote: Seleney
Hey, if you don't want it. Give it back. I want snow!
Come and get it, but bring the better weather with you!

Anyway, the storm is over. We ended up with a little over 3 inches of snow which is considerably less than the NWS and media had been predicting, and right in line with what I originally had in mind before making adjustments… though I never stated anything but 2 to 4 inches on my facebook page outside of the initial 3 to 4 inch prediction the day prior, so woo!


- The system originated somewhere near Colorado, went through Texas, and on Wednesday went through the Ohio Valley.

- Based on its track, I estimated a 7:1 snow:liquid ratio. Based on NWS observations, the actual ratio was 6:1.

- Above freezing surface temperatures created an environment where the snow was melting a lot upon reaching the ground. This likely helped keep the amounts down.

- The massive dry slot that started Wednesday afternoon also kept our amounts down. Don't think anyone really expected that.

- 3.3 inches was the final amount sent to the National Weather Service by someone in my county this morning. I trust it as I measured something around that before work this morning.

- My estimated 2 to 4 inch range (the last given on facebook) was spot on! Hurray!

In reality, I got really lucky with this forecast, I think. A lot of things were pointing towards a more significant snow, but my gut told me it wasn't going to happen. It was just too warm and that massive dry slot definitely helped us not get a lot of snow, though counties to my northwest got hammered just a bit (as I expected).

I'm not sure if I would be able to pull this off again and going against the media and government weather authorities usually isn't the best idea in the world as they know what they're doing better than I do, but it paid off in the end, I guess. You can't always follow along with what everyone else is doing.

With that said, there looks to be another system brewing up for next Wednesday which could produce some very significant snowfall amounts. I'll get to try my luck again, and if you guys are interested I might blog about that one as well.

Edit: Also, if you guys have any questions regarding things about these posts, ask away. I'm feeling like I'm slacking off a bit with my posts and not going into as much detail as I should be, and my recap definitely wasn't the best in the world, either.