General Weather Discussion - April 2015

[bchris02]

Damon Lane posted this outlook for the tornado threat for Saturday, I am thinking this is way overkill for tomorrow ??

https://twitter.com/KOCOdamonlane/st...045313/photo/1

I haven't been paying as much attention to the local media this year as I did the past two years, but I will say it seems like this year KOCO is definitely jumping on the hype train moreso than the other stations.

[venture]

Limiting factors for today getting too out of hand will be moisture. Dewpoints only in the mid 50s and it is fairly shallow moisture as well. HRRR & RAP hinting at some early showers/storms around Noon today over I-35. Then additional scattered development out west ahead of the dryline. SPC is sticking with a SLIGHT for today which could get bumped up based on trends today. We'll just have to wait and see.

[venture]

Upgraded to Enhanced Risk today.

..CENTRAL/SOUTHERN PLAINS...
MORNING WATER VAPOR LOOPS SHOW A PERSISTENT UPPER LOW OVER CO...WITH
SEVERAL SHORTWAVE TROUGHS ROTATING THROUGH THE BASE OF THE LOW INTO
THE SOUTHERN PLAINS. ONE SUCH FEATURE IS EVIDENT OVER SOUTHEAST
NM...WHICH WILL TRACK INTO WEST TX AND EVENTUALLY INTO WESTERN OK
LATER TODAY/TONIGHT. VISIBLE SATELLITE IMAGERY SHOWS POCKETS OF LOW
CLOUDS ALONG THE DRYLINE FROM WESTERN KS INTO WEST-CENTRAL TX...BUT
THOSE CLOUDS WILL LIKELY ERODE BY EARLY AFTERNOON ALLOWING STRONG
HEATING TO TAKE PLACE. DEWPOINTS IN THE 60S AND COOL TEMPERATURES
ALOFT /-16 AND COLDER AT 500MB/ WILL HELP CONTRIBUTE TO AFTERNOON
MLCAPE VALUES OF 1500+ J/KG AND ONLY A WEAK CAP.

SCATTERED THUNDERSTORMS ARE EXPECTED TO FORM ALONG THE ENTIRE LENGTH
OF THE DRYLINE FROM WESTERN KS INTO WEST TX. SUFFICIENT DEEP-LAYER
EFFECTIVE SHEAR WILL SUPPORT SUPERCELL STORM STRUCTURES CAPABLE OF
LARGE HAIL AND PERHAPS DAMAGING WINDS. ISOLATED TORNADOES ARE ALSO
POSSIBLE...BUT WEAK LOW LEVEL VERTICAL SHEAR WILL BE A LIMITING
FACTOR. THE AREA OF PERHAPS GREATEST TORNADO THREAT WOULD BE OVER
WESTERN KS INTO WESTERN NEB WHERE EASTERLY NEAR-SURFACE WINDS WILL
ENHANCE SHEAR. STORMS THROUGHOUT THE RISK AREA SHOULD PERSIST INTO
MID-EVENING BEFORE SLOWLY WEAKENING.

[venture]

[venture]

[venture]

Summary...the severe threat is increasing from south-central ks
across western and central ok into north tx. Large hail will be the
main threat as supercells storms track eastward across the mcd area.
However...a tornado or two cannot be rules out. A watch will likely
be needed in the next hour or two.

Discussion...the severe threat across the mcd area is increasing
this afternoon and a watch will likely be need within the next hour
or so. A surface dryline was analyzed from the eastern ok/tx
panhandles south/southwest to the tx big bend area. Further
east...an outflow boundary was located from parts of south-central
ks into central ok. Some strong thunderstorms had developed along
the boundary...but this is not expected to be the main focus of
severe thunderstorm development this afternoon and evening.
Thunderstorms are expected to develop near the dryline by 22z and
quickly become severe as they track eastward into south-central
ks...western ok and north tx. High resolution models suggest the
current southwesterly low level winds across western ok into western
north tx become become southeasterly before convective initiation
occurs. In fact...18z surface obs at sps and gag have become
southeasterly at around 5-15 kt. This is likely due to weak
cyclogenesis just ahead of the dryline due to weak height falls
resulting from a branch of vorticity ejecting across the tx south
plains into western ok. As a result...a narrow corridor may exist
where the tornado threat will be enhanced briefly across
southwestern ok. This may result in the need for a small tornado
watch across this area...with a severe thunderstorm watch from
south-central ks through central ok into north tx.

Otherwise...moderate instability near 2000+ j/kg sbcape coupled with
steep midlevel lapse rates will lead to a severe hail threat.
Although low level flow is modest...steepening low level lapse rates
with additional heating could also aid in some strong to locally
damaging winds with the strongest storms.

[venture]

[John1744]

Ugh all the local tv mets with their "tornado forecasts" today.

[venture]

Latest radar update. New storm trying to get going in Beckham County, will move NE like the hours and mostly through a pretty open environment. Severe storm by Alva getting ready to go into KS. Next severe storm will be down by Grandfield and will be move NE. HRRR has the storms in that area as the ones impacting the Metro about 7-8PM. We'll have to see.

[venture]

New storm over Chickasha moving NE.

[John1744]

That line is just exploding from the Chickasha storm south east. The main cell north of Chickasha grew fast.

[Bunty]

Severe Thunderstorm Watch Severe Thunderstorm Watch
Updated: Sat Apr-18-15 06:30pm CDT
Effective: Sat Apr-18-15 06:30pm CDT
Expires: Sun Apr-19-15 02:00am CDT

Severity: Severe
Urgency: Expected
Certainty: Likely

Status: Actual
Type: Alert
Category: Met
Areas affected: Atoka; Bryan; Canadian; Carter; Cleveland; Coal; Creek; Garvin; Grady; Hughes; Jefferson; Johnston; Kay; Kingfisher; Lincoln; Logan; Love; Marshall; McClain; Murray; Noble; Okfuskee; Oklahoma; Osage; Pawnee; Payne; Pontotoc; Pottawatomie; Seminole; Stephens

Message summary: Severe thunderstorm watch 77 is in effect until 200 am cdt for the following locations ok . Oklahoma counties included are atoka bryan canadian carter cleveland coal creek garvin grady hughes jefferson johnston kay kingfisher lincoln logan love marshall mcclain murray noble okfuskee oklahoma osage pawnee payne pontotoc pottawatomie seminole stephens

[venture]

We are in the chat right now: Weather Spotlight - Live Chat Room for Weather Event Coverage

[Easy180]

Raced home to south Moore after dinner with our neighbors warning of large hail. Got home just before the winds kicked in but thankfully no hail. Shew!

[Bunty]

A storm bypasses Stillwater by a few miles as thunder is heard from the southeast. Another line of thunderstorms coming in from western Oklahoma may affect OKC and Stillwater, but the southern portion of the line has been weakening.

[venture]

New development along the outflow boundary in NW OK that is moving Southeast. Could see this build down into the metro before it passes.

[venture]

Another busy week coming up...

Severe weather threat today - SLIGHT RISK for the Metro area back to the East with an Enhanced Risk over much of Eastern OK. All modes possible.

Tuesday - SLIGHT RISK over SW OK. MARGINAL RISK for the rest of OK pretty much west of I-35.

Wednesday - 15% risk over much of OK. All modes possible.

[Bunty]

Severe Thunderstorm Watch Severe Thunderstorm Watch
Updated: Sun Apr-19-15 01:40pm CDT
Effective: Sun Apr-19-15 01:40pm CDT
Expires: Sun Apr-19-15 08:00pm CDT

Severity: Severe
Urgency: Expected
Certainty: Likely

Status: Actual
Type: Alert
Category: Met
Areas affected: Adair; Cherokee; Cleveland; Craig; Creek; Delaware; Garvin; Haskell; Hughes; Kay; Latimer; Le Flore; Lincoln; Logan; Mayes; McClain; McIntosh; Muskogee; Noble; Nowata; Okfuskee; Oklahoma; Okmulgee; Osage; Ottawa; Pawnee; Payne; Pittsburg; Pontotoc; Pottawatomie; Rogers; Seminole; Sequoyah; Tulsa; Wagoner; Washington

Message summary: Severe thunderstorm watch 80 is in effect until 800 pm cdt for the following locations ok . Oklahoma counties included are adair cherokee cleveland craig creek delaware garvin haskell hughes kay latimer le flore lincoln logan mayes mcclain mcintosh muskogee noble nowata okfuskee oklahoma okmulgee osage ottawa pawnee payne pittsburg pontotoc pottawatomie rogers seminole sequoyah tulsa wagoner washington

[venture]

[venture]

Storms starting to fire over central OK. Hail big risk...don't be shocked to see a bunch of funnels though.

[venture]

Wednesday's risk has been upgraded to ENHANCED already for most of the Metro area back to Lawton and Wichita Falls and back to the southeast. All modes possible. The Day 3 SPC Discussion...



...SRN PLAINS/ARKLATEX
AN UPPER-LEVEL RIDGE IS FORECAST TO MOVE EWD ACROSS THE SRN ROCKIES
ON WEDNESDAY AS SFC LOW PRESSURE IN THE SRN HIGH PLAINS DEEPENS AND
MOVES SEWD. A WARM FRONT MAY BE PRESENT ACROSS SRN OK EXTENDING
ESEWD INTO AR. ALONG AND SOUTH OF THE BOUNDARY...SFC DEWPOINTS
SHOULD BE IN THE LOWER TO MID 60S WITH MODERATE INSTABILITY
DEVELOPING ACROSS MUCH OF THE WARM SECTOR BY AFTERNOON. AS A CAP
WEAKENS DURING THE DAY...THUNDERSTORM DEVELOPMENT APPEARS POSSIBLE
ALONG THE WARM FRONT AND FURTHER SOUTHEASTWARD ACROSS THE ARKLATEX
NEAR THE ERN EDGE OF THE STRONGEST INSTABILITY. AN MCS WILL BE
POSSIBLE ACROSS THE REGION LATE WEDNESDAY AFTERNOON WITH COLD-POOL
ORGANIZATION ALSO POSSIBLE BY EVENING.

NAM FORECAST SOUNDINGS FROM OKLAHOMA CITY SEWD TO NEAR THE RED RIVER
AT 00Z/THU SHOW MLCAPE IN THE 2000 TO 2500 J/KG RANGE WITH 0-6 KM
SHEAR OF 45 TO 50 KT. THIS WOULD SUPPORT SEVERE STORMS WITH LARGE
HAIL AND WIND DAMAGE. THE MAIN QUESTION IS WHAT STORM MODE WILL
DOMINANT. IF CELLS REMAIN DISCRETE...THEN SUPERCELLS WOULD BE THE
MOST FAVORED STORM TYPE. HOWEVER...THE PATTERN WOULD SUGGEST
COLD-POOL ORGANIZATION WHICH WOULD FAVOR A LINEAR STRUCTURED MCS
WITH ENHANCED WIND DAMAGE POTENTIAL. EITHER WAY...SOME TORNADOES CAN
BE EXPECTED WITH ROTATING CELLS ASSOCIATED WITH THE BETTER ORGANIZED
STORM CLUSTERS. WILL ADD A 30 PERCENT SEVERE PROBABILITY FROM NEAR
AND SOUTH OF OKC SEWD TO NEAR AND EAST OF DALLAS.

FURTHER TO THE SOUTH ACROSS SE TX AND LA...FORECAST SOUNDINGS AT 21Z
ON WEDNESDAY SHOW MODERATE INSTABILITY AND STRONG DEEP-LAYER SHEAR.
DUE TO THIS ENVIRONMENT...CELLS THAT CAN INITIATE ALONG LOCALIZED
CONVERGENCE ZONES COULD ROTATE AND POSE A THREAT FOR WIND DAMAGE AND
HAIL. A SEVERE THREAT COULD ALSO DEVELOP DURING THE LATE EVENING OR
IN THE OVERNIGHT PERIOD AS AN MCS APPROACHES THE REGION FROM THE
NORTHWEST.

[SoonerDave]

A general observation while I wait for a return message on something unrelated

I know the NWS and related orgs have been trying to improve the general means of communication for their severe weather forecast products. I can't help wondering, however, if perhaps we've "slud" too far the wrong direction with fractionally too much information that's either so granular or so vague that it becomes inherently hard to act upon. In turn, that dilutes the value of the information - particularly when local media outlets craft or reshape it in their own vernacular.

For instance, we now have the five-tiered risk outlooks that range from "Marginal" to "high" (and I'll offer immediately from a personal POV that "marginal" and "slight" are completely backwards. TO me, the lowest possible risk should be "slight," as in "barely on the map." It's *very* confusing for me, but then again, lots of things are ) We see other products or features that break down multiple sizes of possible hail, tornado risks, wind risks, again categorized, and then sometimes slotted with respect to probability percentages. On the one hand, there's a lot of information there. On the other, any one piece of information, eg a 15% chance of pea-size hail in location X, that leaves me saying..."okay, I'm not sure what I can do to prepare for that granular a risk?" And when Super Double Doppler Channel 59 Meterologist Guy/Gal Bobbie Joe Schmidlap sees that same kind of data, it immediately gets reinterpreted and recast into Channel 59's deisgnated weather parlance, and makes the problem that much worse for everyone.

Mind you, I understand the difficulty at hand in communicating weather information in this multi-facted media environment. And I know the weather folks are trying to do something different for the sake of improvement, so please don't think I'm being critical. I do get concerned, however, that an abundance of information can lead to what we might call "advisory fatigue." The NWS is wandering toward more of a "nowcasting" format in many of what I'd only expect to be considered forecasts. I mean, a forecast is looking ahead several hours, maybe a few days...but if a given forecast gets updated every...what...15 minutes (???) it really isn't a forecast product any more.

I know I grew up in the day when you had, essentially severe thunderstorm and/or tornado watches and warnings. That was it. And I know we're trying to subtract the fear factor and the Harem Scarem element out (no matter how hard certain, ahem, forecasters try otherwise), and the best way to do that is information. I still think we've yet to find just the right balance.

Thoughts?

[Anonymous.]

I posted something similar earlier this year, the NWS is most definitely shifting to nowcasting. This discussion would be better suited for the Media Coverage thread.

Right now looks like Wednesday will be a weird setup. The overall weather this week and weekend should be amazing, though.

[Roger S]

Right now looks like Wednesday will be a weird setup. The overall weather this week and weekend should be amazing, though.

Hmmmm... Maybe I should consider moving my regularly scheduled Wednesday evening yardwork to this evening?

[venture]

So in my haste, I completely skipped the rest of the week. I'll do a more indepth model review and such late this evening when I get off work.

Thursday severe risk appears to be confined to Southern Oklahoma mostly.

Friday is a day we must watch. SPC is focusing on the Euro solution right now which is showing a strong negatively tilter upper trough moving into the plains. GFS has the reverse with a positive tilt to the trough. Quick Weather School definitions...

A negative trough is when the orientation is roughly from NW to SE, almost like a digging motion. Here is an example (this is not for Friday)...


A good site to use as a quick reference is: WHAT IS A "NEGATIVELY TILTED TROUGH"?

A negative tilt to a trough is, essentially, music to the ears of storm chasers. It indicates a strong storm system, typically good jet stream energy, and a favorable vertical wind shear for upper level events.

So with that, we need to watch Friday because there are indications - if Euro is right - that we will have a negatively tilted trough moving through. The Euro solution at this point has storms firing by early-mid afternoon on Friday over the US 81 corridor. Surface winds would be backed from the southeast with CAPE values exceeding 2000 j/kg by initiation. We need to watch this as SPC is already using very strong wording on a Day 5 outlook, but keep in mind...Euro says one thing - GFS another. This is not set in stone.

MODEL SOLUTIONS DIVERGE
SHARPLY ON FRIDAY/DAY 5 WITH THE ECMWF MOVING AN NEGATIVELY TILTED
UPPER-LEVEL LOW INTO THE CNTRL HIGH PLAINS WHILE THE GFS MOVES A
POSITIVELY TILTED UPPER-LEVEL TROUGH OVER THE SRN HIGH PLAINS AND
CNTRL PLAINS. THE ECMWF SOLUTION WOULD BE FAVORABLE FOR SEVERE
STORMS IN THE SRN AND CNTRL PLAINS WHILE THE FASTER GFS SOLUTION
WOULD BE FAVORABLE FOR SEVERE STORMS OVER THE LOWER TO MID MS
VALLEY. AT THIS POINT...AM LEANING TOWARD THE SLOWER ECMWF SOLUTION
WHICH WOULD MEAN A POSSIBILITY FOR AN ENHANCED SEVERE THREAT IN FROM
NORTH TX NWD INTO SRN KS. LARGE HAIL...WIND DAMAGE AND TORNADOES
WOULD BE POSSIBLE FRIDAY AFTERNOON AND EVENING IN THE SRN PLAINS.
THE POTENTIAL EXISTS FOR AN OUTBREAK OF SEVERE STORMS IF THE ECMWF
SOLUTION VERIFIES. AT THIS POINT...THE LARGE SPREAD IN MODEL
SOLUTIONS IS TOO GREAT TO ADD AN ENHANCED SEVERE THREAT FOR FRIDAY.