Page 5 - Twin & Turbine January 2018

for airports without a TAF. The MOS is derived from the output of weather prediction models such as the North American Mesoscale (NAM) and Global Forecast System (GFS).
Another distinct benefit is that the MOS is updated hourly. You’ll get a refreshed forecast at an airport that will tend to track better with the actual weather. Moreover, MOS is highly tailored for each airport. So, if the airport is in a valley or near an ocean, MOS is aware of the nearby terrain features and local effects of the weather for that airport.
MOS is most accurate in the first six hours and, since it is location specific, will usually provide you with more detailed guidance. One thing to note, however, is that MOS should never be used for legal requirements such as determining an alternate on an IFR flight plan.
Finally, one important way to discern the accuracy of a forecast is to check the forecaster’s confidence. The forecast discussion gives you insight into what the meteorologists at the NWS are thinking and what they believe the models are telling or not telling them.
T o m o r r o w, I a m s c h e d u l e d t o f l y a n A n g e l F l i g h t m i s s i o n a n d the forecast has been a mess. After studying all the resources, I decided to change•the patient hand-off point to a different airport. Sometimes these tools don’t give us what we want, but they can give us what we need to stay safe.
Happy New Year and fly safe throughout 2018. T&T
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