The closed low takes a northerly track into the CWA, treks west, and then slowly moves east and out of the region as the upper level closed low reforms over the SWern states. The time breaks are the same for the WV imagery: Let’s take a look at a few of the satellite images. This is output from the 19.12Z run (if there is a way of retrieving previous model runs, I have yet to figure it out!).Īt this point (mid-event), the models had a pretty good idea of how the atmosphere would behave, but the NAM pinpointed the problem area and timing the best. The top left is the GFS, top right is the ECMWF, bottom left is the SREF, and the bottom right is the NAM. Model output spans the 19.00Z - 21.00Z timeframe. I’ve saved a four-panel of model 500-mb heights, 700 mb wind, 700-500 mb RH and surface precipitation. Although there was uncertainty in timing, location and amounts, it would have provided a heads-up for potential flooding in the general area. This may have been a good time to issue a hydrologic outlook (BOIESFBOI). As an office, we had thought on the 18th that the area of concern would be southern SW Idaho due to a wider model consensus. But as we approached the event date, the model blend seemed to identify the areas of greatest precipitation. There was obviously some uncertainty about what the closed low would do in the model outputs. The last frame is for 12 hours prior to the event. There are 6 frames, each is 12 hours closer to the event.
The models used in this blend are the NAM, the GFS, the SREF, and the ECMWF. Let’s take a look at a model blend of the PoP forecast for the 19th between 00Z and 12Z. On the morning of the 19th, instead of the closed low being centered over SW Idaho (with most of its impacts expected there) and on its way out, the low had moved farther west than we had expected, slowed, and was centered over our CWA for quite some time. We had expected the low to move east a bit faster than it did. The main factors to discuss are the day’s PW values and the track and speed at which the low moved. This was quite an event! So what factors produced this amount of precip? Let’s begin by looking at the storm totals: I’d like to look back at the event and discuss the damage reported after it was over. It seems like we didn’t truly expect the amounts produced, or the longevity of the event. On October 19th, a closed low passed over our CWA dumping a lot of rain before it moved out of the region. Collaborators: Troy Lindquist, Josh Smith, and Les Colin
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