Friday, July 31, 2009

Mike Leuthold Comments re Guaymas Sounding

“I have been noticing an on again/off again problem with the sounding at Guaymas recently and it is occasionally too wet. Today, the error was the largest yet and somehow these bad data made it into the GFS. As you can see from the attachment (see above), the GPS/IPW corrections were huge at Hermosillo and over the far SW part of Arizona. The GFS initialized Guaymas with 56mm whereas the GPS/IPW was 42mm. Yuma was 9mm too wet and Organ Pipe was 6.7mm too wet. The corrections were not applied to the WRF-GFS run from this morning, as the GPS/IPW data were delayed, causing serious havoc within the forecast.

I also looked at the NAM and its IPW field was fine over NW Mexico.

I am surprised such a large error made it into the GFS initialization. Both the temperature profile/moisture profile have a warm/wet bias. It looks to me like a one time error. There is plenty of evidence that the data made it into the GFS as there is a temperature bulls-eye over Guaymas as well as a height field abnormality.”

Mike has sleuthed this out and I am embarrassed that I got sucked-in and highlighted a bad sounding (in hindsight a PW value of almost 3 inches should have set off all kinds of mental alarms). How ironic!

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