As severe
weather marches northeast on Wednesday, Florida residents are drying
out after ludicrous levels of overnight rainfall.
The
National Weather Service called
the event “historic.”
The official rain gauge at Pensacola’s airport measured an
astonishing 5.68 inches in a single hour before it failed around 10
p.m. Tuesday. An
analysis by
the NWS office in Mobile, Alabama, estimated that single hour to be a
1-in-200- to 1-in-500-year event. The official rain gauge and weather
radar both gave
out,
presumably from lightning strikes, so we might never know exactly how
much rain fell Tuesday night.* Still, several
unofficial rain gauges measured impressive
totals.
One
flabbergasted Pensacola resident live-tweeted his rain gauge
throughout the night, ending up with more than 2 feet of rain:
Pensacola’s
highest previous midnight-to-midnight rainfall total was
15.29 inches,
during a land-falling tropical storm in
October 1934.
Local rainfall records go all the way back to 1879, so it’s
possible that Tuesday’s storms produced the heaviest rainfall event
in Pensacola in more than 130 years, even factoring in every
hurricane that has hit north Florida during that time span. To get
five times the typical monthly rainfall in roughly 24 hours is
mind-boggling.
The
overall storm system was monstrous. A strongly pronounced kink in the
jet stream has been effectively stuck in place for days, held fast by
a sluggish
dome of high pressure over
Hudson Bay in Canada. As I wrote earlier
this week,
blocking patterns like this are known for their ability to create
extreme weather.
If
that last image looks like climate change to you, you’d be on the
right track.
It
probably wouldn't be correct to say that climate
change caused Pensacola’s
floods, but it surely made them more likely. Climate change is
playing a role in extreme rainfall events like the one on Tuesday.
The science is here is relatively straightforward: As the atmosphere
warms, it can hold more water vapor. You can see this effect for
yourself on muggy summer days when droplets of condensation form on
the windows of air-conditioned buildings. There’s now more moisture
available that can turn into rain. Warmer days lead to more
evaporation, and more evaporation leads to heavier rainfall.
Essentially,
we’re supercharging the atmosphere by quickening
the hydrologic cycle.
In addition to causing more downpours, these enhanced evaporation
rates are also leading to an increase in drought severity in places
that are already dry, like
California.
In
the context of these greenhouse gas–induced changes to the water
cycle, the addition of an abnormally strong blocking pattern was the
perfect recipe for Tuesday’s epic rains. A bizarre S-shaped storm
system was responsible for funneling incredible amounts of moisture
northward from the Gulf of Mexico.
In
addition to rising global temperatures, the increasing frequency and
intensity of extreme rainfall events is one of the clearest already
observed effects of climate change. While these changes have been
documented in many parts of the globe, it’s more certain that
they’re happening in North America, in part because of better data
here.
In
recent years, a larger percentage of precipitation has come in the
form of intense single-day events. Eight of the top 10 years for
extreme one-day precipitation events have occurred since 1990.
The
freshly released Intergovernmental Panel on Climate Change fifth
assessment report found “high confidence” of a “likely”
overall increase in extreme precipitation events in North America.
Bring an umbrella: Climate change is already increasing the likelihood of downpours.
Heavy
rain and severe weather will continue to lash the East Coast on
Wednesday, with flood watches and warnings currently in effect from
Washington to New York City.
Update,
5:45 p.m.: The National Weather Service in Mobile has confirmed that
Tuesday was the rainiest day since at least 1880 in Pensacola. Using
a blend of rain gauges and nearby radar data, they estimate that
15.55 inches of rain fell during the 24-hour period. This total beat
the old record, measured during a tropical storm, of 15.29 inches.
(Return.)
Baltimore
Landslide
Florida
Highway Completely Destroyed By Two Feet Of Rain
Pensacola,
Florida, is under
water after
flash floods dropped two feet of rain in 26 hours, causing the worst
flooding in Florida in a generation.
Kevin
Roth, lead meteorologist for The Weather Channel, noted that five
inches of rain fell on Pensacola in the hour from 9 to 10 p.m.
Tuesday, which is more than during the entirety of Hurricane Ivan in
2004.
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1
May, 2014
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