October 27, 2009
I hinted at flooding at the middle of this week in one of my posts last week. Then, that same storm transitioned from a minor windstorm to a major windstorm with heavy rain and flooding to practically nothing. Now, we are back with the idea of flooding, with some wind to boot. There are many reasons why the models have had such a difficult time with this moisture and the storm system they are forecasting it to produce, but the biggest reason is that it has residual moisture from Typhoon Neki in it. Models generally have a hard time dealing with tropical moisture. This model shows the precipitable water values in the atmosphere at the time (the total amount of water vapor in inches in a given column of the entire atmosphere).
Here, you can see the 24 hour precipitation amounts for 5 P.M. Thursday to 5 P.M. Friday. It looks like the Puget Sound basin will be rain-shadowed from Everett South (usually it is the other way around). The mountains, on the other hand, will see tremendous amounts of rain. I would not be surprised if isolated spots hosted storm totals as high as eight inches, locally even higher. We’ll be dry tomorrow but the rain will come in late that night and continue into Thursday for the lowlands, while it looks to be a mainly mountain show from there on out.