The Weather Whisper...2018/04/26 · The Weather Whisper May 2019 Volume 1, Issue 1 NWS Des Moines...
Transcript of The Weather Whisper...2018/04/26 · The Weather Whisper May 2019 Volume 1, Issue 1 NWS Des Moines...
Flood Stage Change for the West Fork Des Moines River J e f f Zo g g , S e n i o r H yd r o l o g i s t
The Weather Whisper
May 2019 Volume 1, Issue 1 NWS Des Moines
Cover Photo Credit:
NWS Des Moines Damage Survey at the Iowa Operator Engineers Training
Facility, northwest of Lacona, Iowa.
The morning of August 20th saw
severe storms across the state pro-
duce 3 tornadoes. Extremely strong straight-line winds also produced
widespread damage within Lacona that
was just as intense as was seen in
some of the tornado impacted areas.
Through coordination with
local officials, on July 19th
the NWS in Des Moines
changed the flood stage for
the West Fork Des Moines
River at Estherville from the
old value of 8 feet to the
new value of 10 feet, or an
increase of 2 feet. The NWS
periodically works with local
officials to evaluate flood
stages—and changes them if
necessary—to ensure they
accurately reflect flood-
related impacts.
The NWS considers various
factors in evaluating exist-
ing flood stages and making
recommendations for
changes including a statisti-
cal analysis—analysis of
past crests on the river—and
more importantly, flood-
related impacts. A good
rule of thumb is for the river
to reach flood stage around
once every other year, or
from a statistical perspec-
tive, an annual exceedance
probability of around 50%.
In the case of Estherville,
past crests on the river were
reaching the previous flood
stage multiple times per
year. This frequency of oc-
currence was a red flag that
the flood stage may be set
too low. Statistical analysis
showed that for past crests
to reach flood stage around
once every other year, the
flood stage would have to be
raised by around 2 feet.
Despite what the statistical
analysis may show, the ulti-
mate decision in a change to
flood stage rests with flood-
related impacts and local
officials such as emergency
management. Ideally, flood
stage represents the stage
on the river at which
“significant impacts begin to
life and property within the
reach of the streamgage.”
The “reach of the stream-
gage” is a NWS-specified
distance up and down-
stream from the streamgage
within which the readings,
forecasts, and flood warn-
ings are considered to be
valid. When “significant
impacts” occur, water from
the river typically affects
access and egress, and/or
may flood properties. The
NWS often relies on local
emergency management
and community officials to
provide this information. In
the case of Estherville, local
flood-related impacts sup-
ported raising the flood
stage by 2 feet, because im-
pacts at the previous level
were minimal to none.
River forecasts and flood
warnings for Estherville will
continue to be valid along
the reach of the West Fork
Des Moines River extending
from the Iowa-Minnesota
border to near Wallingford,
reflecting the new flood
stage value. The gauge has
been in operation since
1986, is maintained by the
USGS Central Midwest Wa-
ter Science Center, and
funded cooperatively by the
U.S. Army Corps of Engi-
neers and the USGS .
As with other NWS river
forecast points, the NWS
will provide river forecasts
when the observed or fore-
cast stages go above the
Action Stage. For Esther-
ville, the Action Stage was
also changed on July 19th; it
was raised from 6 feet to 8
feet. In addition, the NWS
will issue river Flood Warn-
ings and follow-up river
Flood Statements when the
observed or forecast stages
go above the Flood Stage.
River forecasts for the above
locations will continue to be
available on the NWS Ad-
vanced Hydrologic Predic-
tion Service (AHPS) Web-
site. River forecasts for
these locations are updated
as needed while the stream
remains at or above the Ac-
tion Stage.
“Ideally, flood stage represents
the stage on the river at which
‘significant impacts begin to life
and property...’“
Flooding on the West Fork Des Moines River
at Estherville, Iowa. Images courtesy of Mike
Ehret and where taken on April 26, 2018.
What’s Your Game Plan? K r i s t y C a r t e r , P a t h wa ys I n t e r n
The days are getting slightly shorter. Tem-
peratures a little cooler. School is back in
session. What else does that mean? Football
season is back! With tailgate season upon
us, it’s important to discuss your severe
weather game plan with your friends, fami-
ly, or fellow tailgaters before heading out to
your favorite tailgate spot or pre-game ac-
tivity since severe weather in Iowa is possi-
ble most of the year. Do you know what the
university, high school, or professional foot-
ball action plan is in the event of severe
weather? Where should you go from the
parking lot if severe weather were to occur
before heading into the stadium?
Tailgaters and tailgating activities can be
vulnerable to lightning, high winds (flying
debris), and heavy rain/flooding. Having a
game plan before the big game could save
your life if severe weather were to strike.
Here are some tips to add to your tailgate
preparations on game day:
Remain weather aware. Check the fore-
cast. Look before departing the house even
if you looked at the forecast earlier in the
week, or the night before, they can change!
Get a good weather app that can provide
weather warnings if needed.
Have a backup way to get those weather
warnings. Phone batteries can die. Consider
a portable NOAA weather radio.
Postpone tailgate activities if you hear
thunder. Return to your vehicle or get to a
sturdy building. Avoid metal objects and
water (puddles), as both are conductors for
electricity.
Heed all NWS warnings. On/near
bleachers, under trees, in a tent, or out in an
open parking lot are all not safe places to be
in thunderstorms, even if you can’t see the
lightning!
Don’t forget about the heat and its poten-
tial effects on your body! (Same with the
cold!)
Severe weather policies and action plans
vary by university, school district, and or-
ganization, so check with your team or tail-
gating location of choice for specifics to stay
safe during your next tailgate. Enjoy the
game!
Fire Weather Season Begins This Month! F r a n k B o k s a , M e t e o r o l o g i s t
The fall fire weather season for central Iowa
typically begins in mid to late September…
once the corn and soybean crops begin their
curing process. In central Iowa we experi-
ence two peaks in the fire weather season.
Each peak has their own threats. In the
spring, when grasses go from dry and
dormant to green, and Iowans are cleaning
areas from yard litter and burning the litter
in ditches when the weather can rapidly
warm and dry out (low humidity), the fire
threat comes from strong southerly winds
carrying embers from the ditches into dry
and mostly cured grass stands.
In the fall, the threat is very different and
actually has two phases. Beginning in Sep-
tember, crops dry and if we get warm and
windy days once crops are dry fires can
quickly spread. The threat early on comes
from farm equipment working it the fields
to harvest crops. Hot machinery can start
corn and bean stubble on fire and the wind
can carry these embers into standing crop
areas and adjacent grasslands. Fires can
quickly grow out of control and become a
danger. We would like to make the farming
community aware of our Grassland and
Crop Fire Danger maps issued in the fall
season to give a heads up to potential dan-
ger. If your area is in a very high or extreme
fire danger, please consider harvesting
when winds are light and humidity levels
are above 25 percent. This information can
be ascertained from our fire weather
webpage at: https://www.weather.gov/
dmx/fire
Towards the end of harvest through Novem-
ber, camping and warm season grass dry
down become the main danger. Be cogni-
zant of the conditions around you and the
dangers of campfires and dry conditions.
Make sure fires are completely extinguished
before leaving them and don’t discard lit
cigarettes and other smoking material into
an open area. Place them in a burn proof
container.
Eugene McAlexander (top left photo) of Beaconsfield, Iowa and Nicky Lenz (top center photo) of Boyer, Iowa were recently honored
for 30 years of service as volunteer observers for the National Weather Service. As observers, Eugene and Nicky send in daily tem-
perature and precipitation measurements, valuable in forecast verification and understanding the local climate. Eugene also re-
cently celebrated is 95th birthday—Happy Birthday, Eugene!
Interim General Manager Shawn Dietz (holding plaque in bottom left photo) receives a 25-year Institutional Length of Service
award on behalf of KLMJ Radio in Hampton, Iowa. Brad Fillbach (left in bottom left photo) presented the award. The NWS has
many institutions like KLMJ Radio that take daily temperatures and precipitation observations for several years.
Bretty Murley of Sac City, Iowa (top right photo) and Meg Beshey (holding award in bottom right photo) both received their 10-year
Length of Service award. Pictured with Meg is Brad (left) and Jeff Johnson, Meteorologist-In-Charge at NWS Des Moines (right).
Weather.gov/desmoines
Editor E-mail:
9607 NW Beaver Drive
Johnston, Iowa 50131
Phone: 515-270-2614
Cooperative Observers Honored for Their Years of Service B r a d F i l l b a c h , O b s e r va t i o n P r o g r a m L e a d e r