THE BIG PICTURE
The weather pattern on October 9 posed some interesting challenges
which I didn't perform well on, with regard to my precipitation
forecast. Let's start by examining the big
picture on this day that my precipitation forecast busted. The
surface map, below, from 12Z on October 9 shows a low pressure
system in the Florida panhandle with a warm front extending over the
Jacksonville area. Also, it shows southerly winds transporting
high dew points to the north toward the low pressure, increasing the possibility for
rain.
This is a surface map from 12Z on October 9 that shows low pressure moving toward Jacksonville, Florida, courtesy of
the
Hydrometeorlogial Prediction Center.
The upper-air pattern appeared unsettled, too. At 500-mb, this
NAM 0-hour forecast valid at 06Z on October 9, below, shows a
strong closed low over eastern Alabama, placing Jacksonville in an area
of divergence which is favorable for showers and thunderstorms. Not
only did the 500-mb pattern appear favorable for rain, the winds at 850mb were forecast to be strong out of the southwest, creating a low level jet stream with high precipitable water values which I thought would create an ideal situation for showers.
This is a 0-hour forecast of 500 mb heights
valid at 06Z October 9, that shows a strong closed low over Alabama creating a favorable environment for rain over
Jacksonville, courtesy of National Center for Environmental Prediction
This Short Range Ensemble Forecast
of 24-hour precipitation ending at 06Z October 10 showed some spread in
solutions as indicated by the colors, with a mean precipitation total
of about .50 inches. On the other hand, these MOS tables from NOAA's Meteorological Development Lab run
on October 8 show only light precipitation amounts during the day
on October 9, much less than the .50 inches suggested by the SREF.
Even though the pattern looked favorable for rain, there was
still some uncertainty. Regardless, I made a precipitation
forecast of .55 inches. This became my biggest forecasting bust
of the Jacksonville period, because, as it turns out, no rain fell at
all. In the next section, I'll explain what I could've done
better and what I learned from this complicated forecast.
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