A Huge Challenge For Next Weekend

The models are going to be in flux this week as they decide what to do with Typhoon Hagibis. The storm is recurving, as typhoons often do this time of year. It is going to be a big early season storm for crab fishermen in the Bering Sea, so for those of you that watch Deadliest Catch in the spring remember this storm. Exactly where its remnants end up is the question. There is also going to be subtropical energy that is going to try to make its way into the southwest US, further confusing the models. Early indications show the remnants from Hagibis driving a small trough into our area Thursday night, which is unlikely to have a significant impact on our weather, however, a much more significant piece of energy shows up Saturday night and Sunday. This is the one to watch, no doubt there will be the potential for a lot of hype with this storm as the operational models are on a wild roller coaster ride.

Meteorologists are trained in these situations to seek the answers and guidance from the ensemble model runs, these “multi-model” are made up of a family of model members, the GFS has 21 members and the Euro has 51 members, each member produces it’s own version of what it thinks will happen, the solutions are blended together to come up with a consensus. Personally, I think a lot of things get missed if a forecaster relies too heavily on the ensembles. They are also low resolution, low-resolution models are horrible for our area with our diverse terrain.

Heavy reliance on ensembles the day before a storm hits usually sets a forecaster up for a big miss. For those of you that followed through the winter a huge example of this was when the Herald wrote a story quoting me saying Durango would get 20 inches of snow and the forecaster at the NWS in Grand Junction said that they didn’t rely on one particular model (ie operational), their blend of models (ensemble) was showing 4 inches of snow. I point this out not to discredit anyone, and I mentioned that after we got the 20+ inches, it is simply what they are trained to do, to fall back on the ensembles.

With all of that being said, we are 7 days out, and taking one particular operational run 7 days away and relying on that for a forecast is actually worse than relying 100% on ensembles the day before a storm hits.  So for the next few days, I will be tracking the ensembles as well as the operational models, by Thursday or so I will switch over to tracking only the operational runs as they approach a consensus solution.

So let’s look at the last couple of operational runs, versus the latest ensemble runs of the Euro and the GFS.

Here is the latest GFS snow forecast for next weekend. I normally would just disregard this and never post it, however, the point the whole point of this is to show how much the models are struggling with this.101306zGFSsnow

Just 6 hours earlier (GFS runs 4 times per day). The same operational model looked like this.


This is why you can trust one operational run. Here is the more balanced ensemble run.


The Euro is also on a roller coaster, although it is a much smaller coaster. Here is the latest Euro operational.


12 hours earlier (Euro runs twice a day) it looked like this.


And here are the Euro ensembles.


I put these up in a particular order because Facebook usually highlights the last photo on my post and I didn’t want the operational models to show up until you read enough of the post to keep things in perspective. So if you skipped over the whole post to look at the pictures you might want to go back and read it before you get excited about that GFS operational run.

Whatever happens with this, it does appear we will get one more chance after this for snow towards the end of the month. My next post will be on Tuesday.


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