LESSONS LEARNED

As I mentioned, I learned some important things as a result of this forecast.  One very important thing I learned about MOS is that wind direction is a MOS temperature predictor.  After looking at the forecast surface map below valid at 12Z October 31 showing a cold front near Green Bay and seeing the change in wind direction on these MOS tables, I predicted a high temperature lower than the actual.  I did this because I automatically thought this front would be strong enough to keep the temperature from rising too dramatically above MOS. What I didn't know was this change in wind direction from southwest to north most likely kept the MOS predicted high temperature a few degrees lower than it should've.   


This is a forecast surface map valid at 12Z October 31, 2008 that shows a cold front passing through Green Bay,
courtesy of the Hydrometeorological Prediction Center.

One more thing I learned is to not just look at the high on MOS when trying to forecast the high temperature.  One reason is MOS typically forecasts daytime highs too cool at locations in the warm sector where it's totally sunny, as it was in Green Bay.  You can see the front arrived at approximately 16Z from seeing the change in wind direction on this series of METARS.  Another look at these MOS tables shows that the winds were predicted to be weak behind the front; therefore, the cold air advection was weak, as well, after the front moved through.  The image below of surface temperature advection valid at 17Z October 31 indicates this was, indeed, the case. In fact, this image of surface plots, from CoolWx, across the state of Wisconsin valid at 17Z October 31shows no wind at all at Green Bay.  

Not only did the MOS tables show the winds would be weak, it indicated the skies would be clear, too.  In late October, solar heating is still more than enough to offset the effects of weak cold air advection. As a result, the temperature stayed in the 60's all afternoon, as this series of METARS shows.  With the clear skies and light winds, the cold front ended up having little impact on Green Bay's weather during the day, much to my dismay.


This is an image of surface temperature advection valid at 17Z October 31, 2008 that shows only weak cold air advection to the north of Green Bay,
courtesy of CoolWx.

A better look at the big picture would've told me just how weak the front probably would be, then, I would've known better how to tweak MOS.  At least, I learned that wind direction is a MOS temperature predictor and how to adjust the MOS temperatures on days similar to this; therefore, I made more mistakes, as the third city in the WxChallenge continued.  Now, let's move onto a busted forecast I made in Quillayute, Washington, but first, I'll start with its climatology.


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