You
can’t beat the ideiocy and blindness of the the mainstream
"No
matter how we look at it, recent events in Oklahoma and Texas have
been rare.....Of course, El Niño alone cannot account for the
record-breaking nature of the rains. We cannot discount the influence
of natural variability of our atmosphere (extreme weather sometimes
just happens), as well as some influence from climate change."
Total rainfall across the Southern Plains in May 2015. NOAA Climate.gov map, based on preliminary data from the PRISM climate group at Oregon State University.
2
June, 2015
We
left off my previous post about the tremendous daily rainfall
event on
May 6 in Oklahoma City with a promise that I would explain what a
one-in-a-100- or 500-year event actually means. Specifically, I was
going to answer how we can even claim such things when records begin
only around 100 years ago.
I
was going to
do this, except it has not stopped raining in Oklahoma and Texas, and
the event itself deserves an update. A constant delivery of the
necessary ingredients for heavy rains has meant record-breaking rains
and flooding spread out over several weeks.
While
no single day in Oklahoma City has come close to the 7 inches of rain
that fell in 24 hours, the city has still received repeated heavy
rainfall for much of the month, including 3.73 inches on May 23. The
city totaled 19.48 inches of rain during the month of May, smashing
not only the previous May record of 14.52 inches (set in 2013), but
also the all-time wettest month on record, which was 14.66 inches in
June 1989. In short, the city has recorded almost 5 inches more rain
than it ever has before in a single month. The city receives only
4.65 inches in May on average.
This
hasn’t been just a wet period for Oklahoma City; the entire state
has recorded a great deal of precipitation. May rainfall has been at
least 200% greater than normal statewide, with southern Oklahoma
seeing rains 400% above average (over 20 inches of rain). For
reference, the 30-day accumulated total (May 2-31) of over 23 inches
of rain near Oklahoma City according to one weather station would be
a greater than a 1-in-1000 year event. This means that every year
there is only a 0.1% that any 30-day period would record that much
rain.
May 2015 rainfall compared to normal (1981-2010). NOAA Climate.gov map based on preliminary data from the PRISM climate group at Oregon State University.
The
wet weather was not simply an Oklahoma affair. Texas has also
received its fair share of drenching rains during the month of May,
and in particular over the last two weeks. From Houston to Austin to
Dallas, torrential one- to two-day rainfall of 4-12 inches has
created havoc. In fact, the suburbs of Houston received up to 11
inches of rain in just 24 hours on May 26. According to the state
climatologist of Texas, the state has averaged 7.54 inches of rain in
May, which is almost an inch higher than the previous record wet
month (June 2004).
Austin
has received 17.59 inches of rain already, beating the previous May
record by 3.49 inches, while Dallas/Fort Worth has also set its
wettest May record by over 3 inches. Overall, in the month of May,
one to two feet of rain has fallen across Texas and Oklahoma, greater
than 200% of normal. Rivers rose rapidly in response to the sudden
influx of water. And just like in Oklahoma City on May 6, the
National Weather Service declared flash flood emergencies for the
hardest hit areas.
Along
the Blanco River in Wimberley, Texas, roughly halfway between Austin
and San Antonio, downpours of rain upstream led to river levels
rising 35 feet in only 3 hours on May 23-24, cresting at least at
40.21 feet, after which the gauge stopped recording. This was 14 feet
above the major flood stage and an amazing 7 feet higher than the
previous record level. Rivers burst their banks all across the state
with flooding in major metropolitan areas, including Austin, Houston,
San Antonio, and Dallas. At least 28 people have lost their
lives, with others still missing.
River levels on the Buffalo Bayou (left) in Houston and the Blanco River (right) in Wimberley, Texas, in late May 2015. The Blanco registered 40.21 feet—7 feet
Combined
together, these individual weather events have made for a
climate-scaled catastrophe and a serious case of weather whiplash.
This region of the United States was suffering from drought
conditions for the better part of the last 4 years. All drought is
expected to disappear due to the recent rains.
The
culprit for these events has been a parade of slow moving storms and
a very moist air mass courtesy of the Gulf of Mexico.
Average wind speed (color) and direction (arrows) at the 300-millibar atmospheric pressure level for May 5-26, 2015. The jet stream persistently steered storms full of moisture into the Southern Plains states of Texas and Oklahoma. NOAA Climate.gov map by Hunter Allen, based on data provided by NOAA Climate Prediction Center.
On
a seasonal climate timescale, above-average rains during the spring
across the southern tier of the U.S., including Texas and Oklahoma,
is a pattern often seen during El Niño events. During El Niños, the
jet stream (an area of fast moving winds high in the atmosphere) can
extend across the southern US, helping to track storms across the
south, including the type of storm systems capable of producing the
severe thunderstorms that soaked the region (compare the above figure
to the wintertime El Niño pattern). During May, this was exactly
what happened, leaving Texas and Oklahoma in a prime location for
stormy weather.
Of
course, El Niño alone cannot account for the record-breaking nature
of the rains. We cannot discount the influence of natural variability
of our atmosphere (extreme weather sometimes just happens), as well
as some influence from climate change, since extreme precipitation
events are likely to increase and have increased as the planet warms
and the atmosphere gets wetter.
No
matter how we look at it, recent events in Oklahoma and Texas have
been rare. From 7-11 inches of rain in one day, to monthly rainfall
amounts never seen before, there has not been a shortage of 1-in-25,
-50, -100, even -1000 year events. Stay tuned for an upcoming post
that gets into the nitty-gritty of how this is done—even when we
only have 100 years’ worth of observations. To get you thinking in
the right direction, remember that just because you don’t have all
the letters in a Wheel of Fortune puzzle doesn’t mean you can’t
figure out the answer
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