IAP 12.310
January 2008
Significant U.S. Weather Events
Florida Pile-up (Jan 8-9, 2008)
(AP Photo/Reinhold Matay)
10 crashes involving 70 vehicles over two miles of I-4 in both
directions: 4 deaths and 38 injured, according to this
Orlando Sentinel.
What happened? It happened in the morning - so was it the fog
(when RH is at its highest)? Was it smoke from a nearby fire? or was
it the combined effects of both?
Although investigators in collaboration with the NWS Tampa are still
determining, we will take a look at what the weather records show.
According to this
time line, the Florida Fish and Wildlife Conservation Commission
lights a controlled burn that was supposed to be limited to 10 acres
on Tuesday morning but spread to 500 acres by evening. A sudden
decrease in RH was the reason given for explaining how the
fire got out of control.
A look at the 10 day meteogram shows, on that particular morning (Jan
8), not only did the temperature increase (which obviously happens
almost every morning), but also there was a sudden drop in dew-point
as well.
This caused the RH to drop 60% in 6 hours. To further
emphasize this, we look at the hourly observation:
Tue Jan 8 13:53:00
2008 16.7 16.7 1025.4 Clear 100
Tue Jan 8 14:53:00 2008 20 17.2 1025.4 Clear 84
Tue Jan 8 15:53:00 2008 22.8 16.1 1025.3 Few 65
Tue Jan 8 16:53:00 2008 23.9 14.4 1024.5 MC 55
Tue Jan 8 17:53:00 2008 25 13.9 1023.4 MC 49
Tue Jan 8 18:53:00 2008 25 9.4 1022.5 Clear 37
(Time, T, T_d, P, Sky, RH)
So the fire continued all day Tuesday and into Wednesday morning.
However, when morning approached, the "normal" fog gets extra "dense"
by all the soot accompanied by the fire. This is an excerpt from
a NWS forecast discussion:
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
933 AM EST WED JAN 9 2008
CORRECTED TYPOS
.UPDATE...WHILE WIDESPREAD FOG WASN`T A BIG ISSUE THIS MORNING...
SMOKE COMBINED WITH THE FOG NEAR INTERSTATE 4 IN POLK COUNTY TO
CAUSE SEVERE DRIVING CONDITIONS WITH VISIBILITY REDUCED TO JUST A
FEW FEET. THIS RESULTED IN NUMEROUS ACCIDENTS AND SPECIAL WEATHER
STATEMENTS HAVE BEEN ISSUED TO COVER.
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