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ClicheVortex2014

March 9-10, 2019 | Severe Weather

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A western trough is going to enter the west coast and push east, possibly becoming a major weather system. Thankfully this setup will not favor significant severe activity in the region that just got devastated. The pattern didn't scream tornado outbreak, but there definitely were signs. This is not the case here.

Starting from the beginning:

A cold front is currently pushing southward and it'll eventually make it to Cuba. 

3Q9HVhG.png

 

On the morning of the 7th, the front will stall out and begin to bring moisture north. Notice the southerly winds in the southern Plains.

NN67Znz.png

 

A system with Pacific origins will strike the Midwest while effectively not having a cold front to push the moisture south. This is very important.

Lvh7tLL.png

6JJUsaZ.png

 

The trough seen off the coast of California in the above image is the trough that this thread will be focused on. By the time the trough crosses the Rockies, there's a decent amount of moisture... but out of context, not as much as one would expect from 2.5 days of southerly winds.

HSkCSb8.png

vWXoNo6.png

 

There's a good deal of uncertainty in amount of moisture return (which is a function of the weak system preceding this) and the speed/strength of this low pressure. Therefore, there's some uncertainty in where the severe threat is, and where it's the greatest. As of right now, it appears to be in the Arkansas/Louisiana/Mississippi area. A GFS sounding from that area shows sufficient CAPE and very strong wind shear. 

2qIBKeh.png

A couple things from CIPS 

Out of 15 analogs for this pattern, 5 were severe weather outbreaks in the aforementioned region. It's also showing a secondary area of severe weather further north near the low, which fits with what the GFS is showing.

DZuvhfE.png

 

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Euro has a significant severe threat for east Texas; 2000-2500 CAPE, 50 knots southwesterly winds at 850mb, 60 knots westerly winds at 500mb. Due to Euro being quite a bit further west than GFS, not expecting SPC to delineate any area yet.

XEYArC2.png

Xy0pLNF.png

PHgtRHM.png

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Great write up. I'm not sleeping on this one, woke up this morning and looked at the 0z GFS and instantly knew there might be something here. 

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SPC has a pretty expansive Day 5 area

 

day5prob.gif.6ff3850385d3139d3f0cb34ed90b403d.gif

 

Quote

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CST Tue Mar 05 2019

   Valid 081200Z - 131200Z

   ...DISCUSSION...
   Medium-range models are in reasonable agreement through roughly Day
   5 (Saturday 3-9), with respect to spatial positioning of the main
   synoptic features.  The GFS remains the more aggressive model with
   respect to deepening of the upper trough as it crosses the Rockies
   Day 4 and the Plains Day 5, and thus likewise depicts a much
   stronger surface cyclone during the Day 5 period.

   Beyond Day 5, the faster GFS outpaces the slower ECMWF, to the
   degree that confidence in the potential for accuracy in a convective
   forecast beyond Day 5 is too low to warrant any areal inclusions.

   In the Day 4 to 5 time range, when model agreement is higher, it
   appears that elevated convection will evolve across portions of
   Oklahoma and Kansas, and possibly northward into Nebraska.  However,
   confidence is not high enough that any hail risk evident at this
   point warrants a Day 4 area.

   Day 5, a surface cold front is progged to sweep across the central
   and southern Plains and into Missouri/Arkansas through the day, and
   then quickly eastward across the Mississippi River into the Ohio and
   Tennessee Valleys overnight.  While the strongest large-scale ascent
   is progged at this time to sweep across the Ozarks vicinity during
   the day, as the trough takes on a negative tilt, substantial
   questions remain as to the degree of moistening/destabilization that
   will be able to occur this far north.  Greater severe risk may
   therefore remain farther south, from east Texas/Louisiana across the
   Lower Mississippi Valley region, and possibly into the central Gulf
   Coast states late.

   Aside from questions regarding instability, this appears likely to
   be a strongly dynamic system with strong flow/shear covering a broad
   area.  As such, damaging winds, and potential for tornadoes, is
   evident at this time.  At this time, a large 15% probability area
   will be issued centered on a north-south zone from Missouri to the
   Lower Mississippi Valley, with additional areal, and risk-level,
   refinements to be made in subsequent outlooks.

   ..Goss.. 03/05/2019

 

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There's no thread, but did anyone see the 2-3" in Jacksonville, NC and surrounding regions?

 

 

20190305_084039.jpg

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SPC went with an interesting approach. 

10 hours ago, Ingyball said:

Great write up. I'm not sleeping on this one, woke up this morning and looked at the 0z GFS and instantly knew there might be something here. 

Thanks. Yeah, the entire pattern screams something's bound to happen but this would be a bigger event if we didn't have a cold front push to Cuba. 

For being the GFS, got some decent parameters. One thing that won't be lacking is shear because of how strong the system will be. Just need better moisture.

4N0F7j0.png

Dwtb15s.png

Southern LA

lEstAmC.png

Eastern MS

3iNBICj.png

 

00z Experimental CIPS analog-based severe probabilities. I haven't seen 15% tornado yet on this, so that's interesting. Keep in mind that I don't think these analogs came after a big Arctic blast, so moisture was probably richer.

Qgm4sgn.png

MWEycVy.png

CIPS analogs based on 00z GFS
XHdf435.png

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12z Euro continues with a more impressive severe threat especially for far east Texas, Arkansas, and at least the west half of Mississippi. Still looking like yet another big negative tilt.

FQSop4N.png

bwXKCeg.png

zBPxqCv.png

 

uTpfvwG.png

33fX7oG.png

xltGSRF.png

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46 minutes ago, ClicheVortex2014 said:

SPC went with an interesting approach. 

Thanks. Yeah, the entire pattern screams something's bound to happen but this would be a bigger event if we didn't have a cold front push to Cuba. 

For being the GFS, got some decent parameters. One thing that won't be lacking is shear because of how strong the system will be. Just need better moisture.

4N0F7j0.png

Dwtb15s.png

Southern LA

lEstAmC.png

Eastern MS

3iNBICj.png

 

00z Experimental CIPS analog-based severe probabilities. I haven't seen 15% tornado yet on this, so that's interesting. Keep in mind that I don't think these analogs came after a big Arctic blast, so moisture was probably richer.

Qgm4sgn.png

MWEycVy.png

CIPS analogs based on 00z GFS
XHdf435.png

Those last CIPS analogs are new to me. Looks identical to the SPC delineation. Wonder if that's what SPC uses for their outlook graphics? I always wondered how they determined the specific shapes they use.

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41 minutes ago, WeatherMonger said:

Those last CIPS analogs are new to me. Looks identical to the SPC delineation. Wonder if that's what SPC uses for their outlook graphics? I always wondered how they determined the specific shapes they use.

Im sure it’s a part of guidance they use but it’s experimental. It’s new and made to be identical to SPC

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12z CIPS analogs has an area that had at least 1 severe report in 73% of the analogs. Within that is an area that had at least 1 tornado in 43% of the analogs.

iK87X5B.png

ykL91Vm.png

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Latest from WPC is interesting. They're saying a squall will be ongoing at 12z Sunday.

WEo32Yt.gif

vkCmfvj.gif

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GFS is still pretty weak with moisture. It does show a sufficient combination of instability and shear to hint at an overnight squall.

fpe9X9Z.png

CF1cBWB.png

6GHVBFa.png

 

Tornado potential in a case of a squall line is best found by looking at the low-level shear. In this case, low-level shear is greatest from 15z-00z, then weakens overnight due to the low occluding and the negative tilt/strongest winds removing itself from the cold front. Therefore, the highest severe threat with the overnight squall would be early, gradually tapering off throughout the night.

GFS has the cold front stalling out just off the Gulf shore. This would set the stage for another system to take advantage of the reservoir of rich moisture created by this system.

rAHd8SJ.png

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GFS 06z 500mb 850mb and Energy Helicity.

1543897176_850mbwindGFS3_6_19.thumb.png.b75be0c5dd8edac5218f9c5dec6761ef.png397388574_500mbwindGFS3_6_19.thumb.png.72b4c85adc77b477260a29008ac354be.png

floop-gfs-2019030606.ehi03.conus.gif.37adbcfc160a818055132f65ca055b59.gif

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This is really a massive area outlined for severe weather. Literally includes all of this subforum.

6FNqve2.gif

Quote

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CST Wed Mar 06 2019

   Valid 091200Z - 141200Z

   ...DISCUSSION...
   Medium-range models appear to be in reasonably good agreement over
   the U.S. through Day 6 (Monday 3-11), with the main upper feature
   early in the period being a negatively-tilted upper trough that will
   move quickly out of the central and southern Plains, across the
   Upper Midwest, and into the Upper Great Lakes Day 4 (Saturday 3-9). 
   As this system continues to progress into eastern Canada and the
   northeastern U.S. Day 5 (Sunday 3-10), a strengthening trough
   farther west is progged to be digging southward along the West
   Coast, before shifting more eastward/inland Day 6.  At this point,
   model agreement deteriorates significantly with eastward
   progression/evolution of this system, and thus forecast confidence
   remains low during the second half of the period.

   In the meantime, widespread showers and thunderstorms are forecast
   to expand across a large area from eastern portions of the central
   and southern Plains early Day 4, eastward/northeastward across the
   Mississippi Valley and into the Ohio and Tennessee Valleys through
   Sunday morning.  Given the strength of this system, and the
   accompanying/strong kinematic field, risk for at least isolated
   severe storms remains evident -- including potential for damaging
   winds and some tornado risk.  However, a primary limiting factor
   appears likely to be limited CAPE (in part due to the widespread
   convective development).  As such, will maintain only 15% risk at
   this time, though strength of this system and accompanying
   deep-layer wind field warrants attention in future outlooks.

   Day 5, models suggest that continued cold frontal advance across the
   East Coast and Gulf Coast states will occur, with the front
   currently progged to reside near both the Atlantic and Gulf Coasts
   near the end of the Day 5 period.  Ahead of the boundary, modest
   CAPE but strong shear is expected, warranting introduction of a 15%
   risk area from the central Gulf Coast to the eastern Carolinas.  

   With the front largely offshore by Day 6, a lull in severe weather
   risk is evident at this time, prior to the advance of the next
   western upper system.

 

WPC has a squall line lasting for more than 24 hours. 

GJLT74W.gif

kdc15ex.gif

 

12z ramped up the event in spatial extent. Shear along the cold front in the south is rather underwhelming. Profiles are also pretty dry. I'm actually more impressed with the soundings up in the Midwest than in the south. Instability is only 300-600 j/kg... about half of down south... but shear is much stronger. 

TeJ2eWU.png

vNLvJ8X.png

 

NAM, on the other hand... LOL. Okay buddy.

uc3cfzu.png

mB5ZudS.png

 

SREF agrees with NAM... like usual

hJRUJfT.gif

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Comparison of the 3 models' surface-based CAPE. Euro is the middle ground between the two, but probably leaning more toward NAM. Like usual.
YJs9zW4.png

oOHWdZ9.png

QhNkYGR.png

 

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My first time seeing 45% contour

OzwWuvf.png

bD7EUag.png

 

Very high sigtor for this far out

5RkVsuP.gif

fwKoOos.gif

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Well... if you're going to be wrong (looking at you, GFS and NAM) at least produce some fun soundings. Thanks NAM. GFS needs to learn a thing or two from you.

uiTGlij.png

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13 minutes ago, ClicheVortex2014 said:

My first time seeing 45% contour

OzwWuvf.png

bD7EUag.png

 

Very high sigtor for this far out

5RkVsuP.gif

fwKoOos.gif

zOWspvR.png.284fea60b5e80f1f6d6b41dd92383a79.png

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gxbaZPE.gif

Quote

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0239 AM CST Thu Mar 07 2019

   Valid 091200Z - 101200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTERED FROM THE
   ARKLATEX/OZARKS EAST TO THE SOUTHERN APPALACHIANS...

   ...SUMMARY...
   A broad area of at least some severe risk is evident from eastern
   fringes of the Plains to the southern Appalachians -- centered over
   the Mississippi Delta Region into the Tennessee Valley Sunday.

   ...Synopsis...
   A strong mid-level trough -- crossing the Plains at the start of the
   period -- is forecast to shift northeastward through the day and
   eventually evolve into a closed low.  By the end of the period, the
   low should reside over the upper Mississippi Valley/western Upper
   Great Lakes vicinity.

   At the surface, a central Plains low should deepen through the day,
   tracking similar to the upper low and reaching the upper Great Lakes
   by Sunday morning.  A trailing cold front will shift rapidly
   east-northeastward across the lower MO/mid MS/OH valleys through the
   period, while sagging much more slowly southeastward along its
   southern fringe.  By the end of the period, expect this front to
   extend from the west slopes of the central Appalachians
   west-southwest across the central Gulf Coast states to the Texas
   coast.

   ...Eastern parts OK/TX eastward to the southern Appalachians...
   A large area of severe potential remains evident at this time, as
   the strong upper trough shifts from the central/southern Plains
   across the upper Midwest and into the upper Mississippi Valley/Great
   Lakes region.  Strong ascent -- focused primarily from the
   Ozarks/Tennessee Valley northward, and a broadly strong/favorable
   wind field, will accompany this system.  However, with widespread
   early-period convection expected, substantial uncertainty remains
   evident.

   At this point, it appears that widespread ongoing/initially elevated
   thunderstorms will spread east/east-northeast out of
   Oklahoma/Kansas, across the Ozarks and into the mid and lower
   Mississippi Valley through the morning/early afternoon.  Storms
   should become increasingly surface-based as low-level theta-e
   advection occurs, but degree of destabilization will largely be
   modulated substantially by the ongoing thunderstorms.  Where the
   airmass can remain unperturbed into the afternoon, strong deep-layer
   shear anticipated across the region would support strong/organized
   updrafts, and thus risk for damaging winds and a few tornadoes.  At
   this time, the most likely axis where conditions may become most
   favorable for a more substantial severe risk appears to exist from
   the Mississippi Delta region, east-northeast across northern
   Mississippi and parts of western Tennessee, and into the Tennessee
   Valley/northwest Alabama.  However, with any corridors of higher
   risk dependent upon details with respect to the evolution of the
   storms, will refrain from introducing any 30% probability contours
   at this time.  

   While severe risk should wane with storms spreading east-northeast
   into the Midwest, where instability should remain minimal, threat
   may linger overnight across portions of the central Gulf Coast
   region near the sagging front -- particularly if this region remains
   largely unaffected by earlier storms.

 

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There's really no need to look at other AFDs after reading this one

LZK

Quote

Area Forecast Discussion
National Weather Service Little Rock AR
250 PM CST Thu Mar 7 2019

.Short Term...Tonight thru Saturday...
All eyes are on Saturday right now, with the incoming system that is
expected to possibly result in severe weather.

Not a whole lot has changed with the dynamics of the system over the
last several model runs. A strong upper level system is continuing
to approach the area and will acquire a negative tilt on Saturday.
The dynamics and wind shear have been highly suggestive of a
potential tornado outbreak, but all along the limiting factor has
been whether or not there would be enough instability.

Prior to today, the GFS/ECMWF/Canadian models were keeping
instability on the low side. The notable exception was yesterday`s
12Z run of the NAM, which started to draw a lot of attention with
CAPE values over 1500 j/kg across much of the area.

Over the last 24 hours all models are showing two trends. First, the
timing of the system appears to be accelerating across the board. It
appears that convection will start in western AR in the morning,
reach central AR by midday, and push into eastern AR by the late
afternoon. Secondly, the models are trending up with expected
instability levels. The 12Z NAM is continuing to lead the pack with
CAPE values as high as 1500-2000 j/kg over central AR, while the
GFS/ECMWF clock in around 850-1250, and the Canadian lags at 750-
1050.

This upward trend is concerning considering all of the dynamic
energy with this system. At the moment there are three question
that are on my mind.

The first question is...how far north with the warm front advance?
The front will be advancing northward across the area which should
bring plenty of warm, moist, and unstable air into the region, but
the ECMWF/Canadian models are lagging quite a bit with this front,
and barely get it north of central AR before the following cold
front sweeps thru. The NAM/GFS favor the front getting all the way
into northern AR, but I cannot help but remember a recent system
that had a problems getting a warm front to advance far enough to
the north for severe weather. Much of the state remained in the cold
sector and didn`t experience much of anything. Will this system be
different? I am fairly confident the warm front will make it north
of central AR, but do have some concerns about it making it all
the way north of the AR border.

My second question is...how will the timing of this system evolve?
If the system continues to accelerate, the risk may be lower across
the western portions of the area. For the moment I will stick with
the median timing provided by the models, but this will require
close monitoring.

The last question is, will there be any significant upper level
support? There appears to be a split in the southern stream of the
jet, and I am not particularly confident in any of the model
solutions at the moment. My gut feeling is that support will
increase markedly as the storm system moves into the eastern part of
the area.

Putting it all together, with the timing, instability, wind shear,
and (probably) more favorable dynamics toward the east...I think
that the system will likely begin with a QLCS across western AR in
the morning that will intensify as it moves eastward. Some
supercells may develop ahead of the line as it moves across the
state. I think areas near the warm front will be a concern for
possible tornadoes, albeit with less CAPE. And storms across the
eastern portions of the state (especially the southeast) will be in
a more favorable region for the development of rotating storms.

 

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Not going to say I'm rooting for tornadoes, but this area is the zone that showed up in my analogs when I googled tornado outbreaks in March for the years I selected. I think the outbreak next week will be worse for severe weather than this one overall, but we'll see.

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4 minutes ago, raindancewx said:

Not going to say I'm rooting for tornadoes, but this area is the zone that showed up in my analogs when I googled tornado outbreaks in March for the years I selected. I think the outbreak next week will be worse for severe weather than this one overall, but we'll see.

Ominous. It was already troubling but this is another bad sign. 

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8 minutes ago, raindancewx said:

Not going to say I'm rooting for tornadoes, but this area is the zone that showed up in my analogs when I googled tornado outbreaks in March for the years I selected. I think the outbreak next week will be worse for severe weather than this one overall, but we'll see.

Yeah, lots of uncertainty with Saturday though regarding moisture and how far the warm front will actually go. But I agree about next week. Like I said in the spring thread, that setup reminds me of a multi-day severe outbreak sequence you'd see in May... except further south.

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These are the tornado outbreaks I used for my March tornado zone on my March forecast map -

https://en.wikipedia.org/wiki/March_1942_tornado_outbreak

https://en.wikipedia.org/wiki/Tornadoes_of_1970#March

https://en.wikipedia.org/wiki/Tornadoes_of_2005#March_21–22

My blend was 1942, 1958, 1970, 1975, 1999, 2005, 2010, 2015, with 1942, 1970, 1975, 2005, 2010 weighted twice, 1958 weighted three times. 1942, 1970, 2005 are all El Nino Springs - but they followed major hurricanes hitting the Gulf Coast, which for whatever always seems to precede incredible cold in the Western half of North America from mid-Feb to mid-Apr, usually March. The link actually shows March 2005 had over 100 tornadoes.

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Comparison of GFS, NAM, and HRRR for Saturday morning. GFS has much more warm sector precip and lower dew points, but a further north warm front. HRRR and NAM are very similar pretty much every way you cut it. They have the dry warm sector scenario covered which is the most ominous. HRRR's great resolution shows that the MCS has already formed by 12z... I'd guess that would travel east-northeast while some cells pop on its south side. 

z94aEoZ.png

FC8ouz1.png

2X9C1hB.png

 

0WGd4JB.png

nLJrGtd.png

4wpo6ev.png

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