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Joe’s Weather Blog: Ice Storm Warning issued (THU-1/12)

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As expected the entire area has been placed under an Ice Storm Warning into the weekend. Significant accumulations of ice are expected in the area. I have a lot to write about today and only about an hour to do it. I will be doing a Facebook Live starting at around 4PM with additional details about the unfolding scenario. I also spent part of my afternoon talking  to a friend of mine regarding the power line situation which I wanted to write about as well.

Forecast:

Tonight: Fair skies and cold with lows in the teens

Friday: Quickly turning gray and overcast. Temperatures will struggle in the mid 20s. There is a chance of some light freezing mist/drizzle/showers developing towards the afternoon…near or after lunch, especially from KC southwards. Road treatments will help us on this round. Untreated surfaces though may get a light glaze.

Saturday: There may not be a lot happening for most of the daylight hours. Cloudy with some patchy freezing drizzle/mist. Temperatures in the 20s to near 30°

Sunday: What worse part of the storm occurs should happen before the game. There are still questions about how bad it will really be BUT my suggestion is to prepare for ice accumulations of 1/4-1/2″+ and slick driving conditions. What falls towards and after 3PM should be liquid as opposed to frozen.

Discussion:

I want to start with something that I put on my FB page earlier this morning. Feel free to “LIKE” that page for additional updates and live weather inserts

capture

I don’t know how much clearer I can put things…and my goal today in describing the unfolding events was that IN MY OPINION this WAS NOT going to be a repeat of 2002 in terms of the massive power issues that occurred back then. Can something change…sure…but this is where I’m at right now and hopefully this is the way things play out.

There are still questions, as expected, about the heaviest areas of freezing rain. Again for those who are joining the party late…there will not be any snow of noteworthiness with this event. It’s just too warm just above the surface for that to happen.

I talked to a friend of mine from KCP & L today…and we were talking about the potential power issues (or hopefully lack thereof). The system overall is rated to be able to mostly withstand 1/2″ of ice and 40 MPH winds (the wind factor is VERY important in these scenarios). We’re going to have more “wiggle room” with this event because we’re not expecting that much wind, unlike in 2002 when the winds were a BIGGER issue. Less wind…more ice load capabilities of the power lines. Things were so bad in 2002 that those high power transmission lines were “galloping”. This is what that phenomena looks like (sorry for music)

So that scenario will NOT be in play with this coming weekend’s event.

With that said…again as I mentioned yesterday…would it shock me if some had a power issue…no. I just don’t think it will be that terrible overall if you know what I mean. Regardless…I would hate to be without power on Sunday with a certain football game on.

Next item…I know many are looking at the model output of expected liquid equivalent of rainfall. Last night I was at our local AMS chapter meeting talking to some of my colleagues about ice “accretion”. Fancy word I realize…basically about how ice accumulates. Just because our models may crank out 1/4-1 1/4″ of liquid doesn’t mean that 1″ of “moisture will collect on the power lines…actually far from it.

Some colleagues of mine from the NWS in Topeka have created a new model that is getting more acceptance within the NWS across the country. The model is called the FRAM model. This model has proven in over 1500 hours of icing observations.  A couple of takeaways IF I understand the model parameters correctly. Let’s say you get 1″ of freezing rain (liquid equivalent). Due to various elements including the rate of rain/hour and other things…that 1″ of rain will freeze into roughly .7>.8″ of ice. On a radial surface though, for example a power line or a tree limb, due to dripping effects due to higher rain rates in some cases, the accumulation will be MUCH LOWER…closer to 30-40% or so of the total possible in a perfect world (1”). What does all that mean…well in a weird way…a long term slow freezing rain event actually accumulates on wires and tree limbs MUCH more efficiently than a faster and heavier event that doesn’t last for as long. On a horizontal surface, such as a solid table top or something along those lines…the ice accumulates faster.

Here is one of their graphics showing what I’m trying to explain…

capture

Courtesy: Brian L. Barjenbruch & Kristopher J. Sanders NWS Topeka, KS

I hope that all makes sense.

So now let’s move on to this little item that I dug up today. The KS Forestry Department did a study about how urban trees fared during icing events…they came up with the trees that did the worst and the trees that did the best in those situations.

So there’s that…needless to say there are a lot of the “susceptible” trees in our area as we are aware of.

Ice can add to the weight of a tree limb by a factor of 30 and each 1/2″ of ice adds 500 lbs to the weight of power lines that are long enough.

OK so where are we with regards to our system. Well it’s onshore now in western CA. You can see it clearly on the water vapor loop.

Let’s go up to about 18,000 feet and track the progress of this…into the weekend using the NAM model

I think you can clearly see the progress of the system as it drops into Mexico then cuts out into the western Plains on Sunday.

The various model solutions are still throwing low confidence into where exactly the heaviest areas of freezing rain will set up. For the purpose of this blog…I’m taking the freezing rain (liquid equivalents) through Noon Sunday,. After that we should see a transition from south to north into liquid.

The 18Z GFS model…

gfs_tprecip_kc_14

GFS 18Z model

ecmwf_tprecip_kc_14

EURO model

nam_total_precip_kc_25

Monkeywrench ALERT…the NAM model

Let’s assume the NAM model is off…BUT again it highlights the LACK of clarity when it comes to the location of the heaviest amounts…again this is expected and should resolve a bit better tomorrow. ALSO REMEMBER as I wrote about earlier…this isn’t a 1:1 conversion to ice accumulation. Cut this 20-30% for icing and another 40-50% for icing on a power line accumulation.

More coming soon.

Feature photo is from John Carter…of the 2002 ice storm of course

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FB Time.

Joe

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