October 28,2013
When people think of severe weather, they probably think of springtime. But fall is another part of year when meteorologists expect hail, high winds, and even tornadoes.
As the last week of October begins, severe weather will once again rear its head, bringing periods thunder and lightning from the Plains to the Mississippi Valley.
(MORE: Tornadoes in October, November: Fall Considered Second Severe Season)
We’ve been telling you that severe thunderstorms will be rumbling, but what meteorological elements are coming together for this late season event? Below is a day-by-day analysis of the ingredients that could help create this week’s severe weather.
Tuesday, Oct. 29
Tuesday looks like a pretty marginal day for severe weather and that’s welcome news for people that live in the eastern Texas Panhandle and southwest Oklahoma.(MORE: Halloween Week Severe Storm Threat)
Even so, some parameters are coming together to produce rough weather.
Tuesday's Severe Ingedients
- Moisture: As a big
low-pressure system moves over the Rockies, it’s helping to draw
moisture up from the Gulf of Mexico. Moisture is a key component in
determining the buoyancy – or how easily air can move up and down. If
the air is buoyant, it makes storm initiation much easier. Dew points
will be high, in the mid and upper 60s.
- Energy:
Energy – more specifically CAPE, or Convective Available Potential
Energy – is integrally linked to moisture and helps meteorologists
determine the atmosphere’s instability. Generally, the higher the
moisture, the higher the CAPE. CAPE can also give us an idea of how
strong thunderstorm updrafts might be, and that allows meteorologists to
have insight into the robustness of potential storms that develop.
Tuesday, CAPE values will be in the 2,000 J/kg range. That’s high
enough the warrant some concern, but not all that alarming.
- Forcing: Forcing
is a general term that meteorologists use to describe how certain
atmospheric features – like a front – will affect an air mass. Think of
it this way: A bulldozer uses force to move dirt forward. A frontal
feature, like a cold front or dryline, is a forcing mechanism that
pushes air forward and up. Tuesday, a dryline – a line where warm,
moist air is on one side and dry, hot air is on another – will push
through the Plains Tuesday, helping to fire off storms.
- Mid-level Temperature: Around 700 millibars, or roughly 10,000 feet in the air, meteorologists focus on the atmosphere’s temperature. More specifically, we’re looking at a temperature inversion. That’s where this area of the atmosphere is warmer than parts above or below it. It acts as a barrier to rising air. Think of a lid on a pot of boiling water: the lid traps the hot air and when you remove the lid, hot air races up. That’s kind of how an atmospheric capping inversion works. If the cap is too strong, the severe weather potential is pretty limited. Tuesday’s cap looks pretty strong at this time.
Wednesday, Oct. 30
The chance for severe weather will increase as the low over the Rockies pushes out over the Plains states. Hail, high winds, and isolated tornadoes will be possible later in the afternoon. The severe threat will shift further east, including an area from North Texas to northern Missouri.(MORE: TWC's Exclusive TOR:CON Index)
Here’s what we know:
- Moisture: As
a strong low-pressure ejects into the midsection of the country,
moisture will continue to stream north. Dew points in the mid and upper
60s will reach further north than Kansas City.
- Energy:
CAPE will be a bit more limited than on Tuesday. Forecast models are
predicting about 1,000 J/kg of CAPE over central Oklahoma and
south-central Kansas, but this is subject to change. If the sun peeks
out for a couple of hours, the atmosphere could become more
destabilized.
- Forcing: The dryline will be
less of a feature on Wednesday, as the cold front overtakes it. That
said, the cold front should provide sufficient lift to fire off some
thunderstorms.
- Mid-level Temperature: The capping inversion will be less of a detriment to development on Wednesday. This layer of the atmosphere will be a bit cooler over the main threat area, essentially lessening the “lid effect.”
Thursday, Oct. 31
Weather on Halloween could be pretty scary from some in and around the lower Mississippi River Valley and the Tennessee River Valley. Hail, high winds and isolated tornadoes are all possible.(MORE: Looking Inside a Hailstone)
Thursday's Severe Ingredients
- Moisture: A stream
of moisture will continue pouring into the Southeast. Dew points will
be in the upper 60s area-wide. Dew points in the 70s, closer to the
coast, aren’t out of the question.
- Energy:
At this point, CAPE looks pretty limited on Thursday, around 500 j/kg.
This forecast is definitely subject to change between now and then. If
more sunshine is forecasted, instability could increase.
- Forcing:
The cold front will continue its eastward march as the parent
low-pressure system pulls up to the northeast. The majority of the
storm activity will focus on the front.
- Mid-level Temperature: The capping inversion, much like on Wednesday, won’t have much of an impact on storm development.
It’s important that you remain weather-aware over the next couple of days. Check back with us frequently, we’ve got all the information you need.
MORE: Mitch Dobrowner - Storms
Texline, Texas
'Mammatus', Texline, Texas, 2009 from 'Storms', photographs by Mitch Dobrowner (Aperture, 2013)
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