Sometimes a forecast goes wrong..

One often learns a great deal from failures, and certainly Friday was not a great success for my profession....and it serves as a good illustration of how useful weather radar information is when the computer forecast models have problems.

The weather predictions for Friday afternoon was for relatively warm conditions  (70F for Seattle, 72 Tacoma) with only a slight chance of rain (roughly 10%). 

 The computer models did not show any rain over western Washington, such as this prediction by the NWS NAM model for the three hours ending at 2 PM:

 Or the UW WRF for the same period:

 Similar to solution to the NWS model.  And yes, my forecast for KPLU--made around 7:30 AM, and before the precipitation was obvious in the radar, was too dry and warm as well.

It became evident in the morning hours that the models were missing a major ingredient as precpitation was evident offshore and then moved in over us--thanks to the new Langley Hill radar (images at 10:30 AM and 12:03PM):

Most of this precipitation was due to mid-level instability (and convection) and very little reached the surface.  Thus in some sense the model verifications really weren't that bad...but the cloudiness resulted in the max temperature being well below the predicted and the edge taken off a supposedly nice day.  Sea Tac for example only reached 65F...5F below the forecast.

Here is a nice video showing the development of the mid-level convection:

http://www.atmos.washington.edu/~ovens/loops/flash2.cgi?/images/webcam2/movies/20110930.swf

So if one watched the radar carefully, you could have seen the forecast going wrongand alter it....we call this nowcasting.

So what went wrong?   There appear that there was a weak offshore disturbance that was poorly described in the initial state of our numerical models.  Here is the 9:30 AM infrared satellite photo that suggests such a feature:

During the next few months the NWS and the UW will be using the information from the Langley Hill radar to initialize our models, perhaps this will help improve the short-term forecasts of such events, but it will do little to help predictions more that 6 hours out.  To improve these will require better use of satellite data and more satellite data.

Note:  The Camano Island radar is down now for upgrading to dual-polarizaton...should be up by the end of the week....cliff


DOG Alert

We had a solid spotter report of my lost cockapoo in Mountlake Terrace near Terrace Creek Park...if any of you live or work up there can you keep an eye out?  For a picture of her, check the link on the right.  Thank you so much. 
http://misscockapoo.blogspot.com/2011/09/missing-black-female-cockapoo.html
Here is the area she was seen last in:

 

This dog was lost on 9/10 and has moved 10 miles in 19 days.