General Weather Discussion - April 2014

[venture]

Reed Timmer works for ratings, and only ratings. He is a very bright guy, but I'm not sure why anyone would take his opinion over other professionals, especially when the hype machine has been known to be in effect.

Some of the models have me doubting a large scale outbreak (particularly tornadoes) on Saturday. Moisture return seems to be getting increasingly meager on the models, and yesterday's dewpoints verified much lower than models had it. The drought is doing its magic. It wouldn't totally shock me to see just a few supercells go up. Unfortunately, meager or not, the moisture return is expected to increase right around sunset, so it wouldn't shock me if the tornado threat existed into the night which is obviously no good -- but I'm not sure I'm seeing epic outbreak on Saturday like maybe I once was. Still some nasty analogs being noted by CIPS, but that's assuming the modeled dewpoint values are correct (among other things).

This sums it up well...on both Saturday and Timmer.

Winds from the SSE or SE empirically bring back more moisture as they're typically sourced out of the Gulf of Mexico, bringing in buckets of humidity to fuel a storm-favorable environment.

Exactly.

[venture]

12Z NAM and GFS all but eliminate any severe threat Sunday along and west of I-35 for the main show - anything overnight/left over from Saturday is not included in this. Until we start to see a reversal and slowing of the dryline's progression, there just isn't going to be much of a threat to the area and west.

Saturday the models can't agree on where things will pop. Overall setup hasn't really changed. The moisture return on GFS is pathetic...waiting until Saturday morning for richer moisture to work back up here - which isn't going to be in time for any significant. It'll be like yesterday where dewpoints did creep up pretty good, but the depth of quality moisture was terrible.

I've been trying to stay fairly neutral but I'm going to show a bit more pessimism on the setup unless things change. I also am reminded that this is still April. In my experience the better setups have always seems to race through and impact Eastern OK more.

[ou48A]

SPC SREF SREF_prob_sigtor_5_
?

[venture]

SPC SREF SREF_prob_sigtor_5_
?

Did you have a question about that product?

[ou48A]

Did you have a question about that product?

I have never seen this before.....I guess I should have ask how accurate is it?

[venture]

I have never seen this before.....I guess I should have ask how accurate is it?

Sig Tor is a product that's been around awhile. I've linked it in the past as it is also available from some of the model runs. It usually holds some weight in paying attention, but it also needs to be used in conjunction with what is actually going on. The version you link for example. It shows a pretty focused area and moderate/high SIGTOR values over SW OK early this morning at about 4AM. Of course - there wasn't any tornadic weather at that time. We really need to have other factors line up for SIGTOR to be worth anyone's time. If there is on going storms at the time, or storms are expected to form, and other conditions are favorable for convective development - then we would look at SIGTOR to get an idea on tornado potential and risk for a strong tornado. It is also important to watch the time stamps of the forecast. Anytime after dark and through the morning hours will normally showcase moderate SIGTOR values just because it is when we normally have higher shear and helicity values. While CAPE, CIN, and LCL height are factors in the equation so is bulk wind shear and storm relative helicity. Those last two can make things look worse than they are. Now. Last year during the May tornadoes, we did have higher SIGTOR values during convective activity so it lined up and actually meant something.

For those that want to see the math: Significant Tornado Parameter (STP)

Sig Tor (CIN) = (mlCAPE / 1500 J/kg) * (ESRH / 150 m2/s2) * (EBWD / 12 m/s) * ((2000 - mlLCL) / 1000) * ((mlCINH + 200) / 150)

[venture]

Okay I've been debating putting this out there, and have discussed it with others here about it, but I think it might be important to do so since it is floating around on facebook pages and other forums.

CIPS, the Cooperative Institute for Precipitation Systems, puts out a product title CIPS Analog Guidance. What this does is compare upcoming events to previous events that share similar environmental setups. It is not 100% accurate and just gives us another tool to use and compare to what could happen with what has happened in the past. It doesn't mean it will do what it did on these past dates, but it allows us to compare with the faults and successes of those setups. So when you hear some drama queens going on about how this weekend matches a big day in the past, this is probably what they are using to pull those dates from.

So for Saturday, here is the 12Z NAM Analogs: CIPS Analog Guidance: Southern Plains F060

Top Analogs - Scores:

Columns in the table are sortable by header. For more information about a specific event, click on the date. A perfect field score is 1.0. The final score weights 850HGHT 3 times, 850TMP 2 times. The maximum final score is 14

DATE	300HGHT	500HGHT	850HGHT	850SPED	PMSL	850TMP	850MIXR	2mTMP	2mDWP	AVGRELH	PWTR	F054	F060	F066	FINAL
19840426/0000	0.940	0.946	0.957	0.911	0.950	0.755	0.894	0.834	0.830	0.863	0.937	11.841	12.489	12.468	12.266
20110410/0000	0.915	0.920	0.948	0.895	0.923	0.842	0.854	0.871	0.830	0.845	0.929	11.761	12.509	12.420	12.230
19990504/0000	0.860	0.869	0.937	0.907	0.935	0.756	0.882	0.845	0.872	0.882	0.947	11.981	12.321	12.379	12.227
20050405/0000	0.871	0.864	0.865	0.928	0.928	0.805	0.858	0.869	0.905	0.874	0.919	12.194	12.222	12.165	12.194
20060406/0600	0.887	0.864	0.933	0.889	0.933	0.824	0.789	0.773	0.813	0.821	0.893	12.215	12.108	12.037	12.120
19940425/0600	0.844	0.919	0.929	0.878	0.928	0.830	0.866	0.748	0.813	0.839	0.931	11.702	12.212	12.239	12.051
20110510/0000	0.909	0.915	0.889	0.823	0.906	0.865	0.836	0.842	0.798	0.869	0.915	12.209	12.209	11.620	12.013
19890427/0000	0.847	0.877	0.884	0.747	0.868	0.918	0.825	0.907	0.892	0.802	0.918	12.141	12.171	11.588	11.967
19820402/0600	0.902	0.903	0.913	0.878	0.919	0.723	0.864	0.586	0.769	0.770	0.895	11.778	11.671	12.388	11.946
19910326/0000	0.785	0.880	0.911	0.927	0.925	0.812	0.866	0.919	0.853	0.824	0.913	11.888	12.248	11.630	11.922
19850511/0000	0.799	0.846	0.904	0.821	0.929	0.841	0.832	0.888	0.804	0.794	0.892	11.642	11.999	12.116	11.919
19930607/0600	0.868	0.908	0.938	0.856	0.918	0.833	0.703	0.842	0.679	0.805	0.843	11.667	11.901	11.922	11.830
20060330/0600	0.907	0.917	0.945	0.873	0.940	0.736	0.822	0.603	0.670	0.803	0.921	11.648	11.763	11.979	11.797
20070607/0000	0.774	0.860	0.950	0.845	0.957	0.807	0.795	0.844	0.825	0.849	0.909	11.724	12.119	11.542	11.795
20020418/0600	0.795	0.832	0.922	0.801	0.923	0.867	0.782	0.776	0.790	0.805	0.906	11.931	11.908	11.546	11.795

ENSO Phase Occurring with Analog: Warm , Cold , and Neutral

Note: ESNO phases are for reference only and are not used in the selection and rank of individual analogs.

For the 12Z GFS: CIPS Analog Guidance: Southern Plains F084

Top Analogs - Scores:

Columns in the table are sortable by header. For more information about a specific event, click on the date. A perfect field score is 1.0. The final score weights 850HGHT 3 times, 850TMP 2 times. The maximum final score is 14

DATE	300HGHT	500HGHT	850HGHT	850SPED	PMSL	850TMP	850MIXR	2mTMP	2mDWP	AVGRELH	PWTR	F078	F084	F090	FINAL
20050410/0000	0.895	0.855	0.941	0.923	0.958	0.875	0.875	0.852	0.901	0.810	0.894	11.850	12.534	12.214	12.199
19990504/0000	0.853	0.824	0.898	0.939	0.940	0.885	0.829	0.814	0.916	0.758	0.901	11.685	12.239	12.637	12.187
19840426/0000	0.917	0.902	0.898	0.828	0.928	0.911	0.804	0.809	0.851	0.809	0.864	11.789	12.227	12.436	12.151
19910412/0000	0.911	0.935	0.965	0.848	0.922	0.892	0.887	0.767	0.917	0.769	0.886	11.721	12.523	12.202	12.149
20050508/0000	0.883	0.878	0.931	0.916	0.937	0.836	0.872	0.858	0.891	0.809	0.914	12.186	12.422	11.722	12.110
19940425/0000	0.873	0.888	0.941	0.896	0.953	0.861	0.858	0.861	0.875	0.806	0.897	12.089	12.450	11.735	12.091
19910326/0000	0.817	0.874	0.912	0.893	0.956	0.890	0.851	0.902	0.858	0.712	0.861	12.043	12.239	11.855	12.046
19850422/0000	0.799	0.772	0.952	0.911	0.956	0.860	0.865	0.760	0.914	0.776	0.888	11.604	12.219	12.255	12.026
19840315/0000	0.878	0.806	0.913	0.915	0.951	0.868	0.858	0.813	0.852	0.815	0.892	12.078	12.254	11.689	12.007
20100430/0000	0.819	0.834	0.871	0.845	0.899	0.942	0.825	0.914	0.886	0.781	0.861	11.692	12.161	12.126	11.993
20120415/0000	0.789	0.862	0.930	0.875	0.937	0.870	0.848	0.792	0.949	0.804	0.897	11.498	12.282	12.169	11.983
19980514/0000	0.904	0.880	0.915	0.922	0.901	0.906	0.798	0.774	0.853	0.814	0.888	11.865	12.291	11.776	11.977
19810328/0000	0.964	0.969	0.948	0.939	0.951	0.813	0.822	0.854	0.797	0.783	0.873	11.823	12.425	11.664	11.971
19990510/0000	0.673	0.748	0.911	0.952	0.923	0.929	0.842	0.862	0.876	0.858	0.893	11.986	12.216	11.624	11.942
19820402/0000	0.852	0.834	0.911	0.915	0.951	0.890	0.842	0.880	0.876	0.714	0.852	11.670	12.229	11.856	11.918

ENSO Phase Occurring with Analog: Warm , Cold , and Neutral

Note: ESNO phases are for reference only and are not used in the selection and rank of individual analogs.

[venture]

MESOSCALE DISCUSSION 0394
NWS STORM PREDICTION CENTER NORMAN OK
0113 PM CDT THU APR 24 2014

AREAS AFFECTED...PORTIONS OF ERN OK AND WRN/CNTRL AR

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 241813Z - 242015Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...THE RISK FOR SEVERE THUNDERSTORMS WILL INCREASE THIS
AFTERNOON...POTENTIALLY REQUIRING WW ISSUANCE.

DISCUSSION...SFC MESO-ANALYSIS INDICATES A STRONG COLD FRONT
CONTINUING TO TRACK EWD ACROSS ERN OK. FRONTAL ASCENT AND STRONG
DCVA PRECEDING A PV MAX WILL CONTINUE TO SUPPORT AN EWD PROGRESSION
OF ONGOING CONVECTION. DESPITE CAPPING EVIDENT IN THE 12Z OUN
RAOB...ALSO SIGNALED BY STANDING WAVE CLOUD FORMATIONS/BILLOWS OVER
THE OUACHITA MOUNTAINS...DIURNAL PRE-FRONTAL HEATING WILL CONTINUE
TO SUPPORT AN EROSION OF ANTECEDENT MLCINH WITH MLCAPE INCREASING TO
AROUND 1000-1500 J/KG. AS SUCH...FRONTAL CONVECTION SHOULD INTENSIFY
AS IT SPREADS ACROSS THE REGION. FURTHERMORE...PREFRONTAL ISENTROPIC
ASCENT -- MAXIMIZED INVOF A REMNANT/DECAYING OUTFLOW BOUNDARY
ANALYZED FROM SERN OK TO CNTRL/S-CNTRL AR -- MAY CONTINUE TO BOLSTER
CONVECTION IN ITS VICINITY INTO THE AFTERNOON. THIS WOULD OCCUR AS
SFC WINDS VEER TO THE SSW /PER RECENT OBS/ AND SUPPORT THE INFLUX OF
RICHER MOISTURE AND AN INCREASE IN BUOYANCY. GIVEN FAST MID-LEVEL
FLOW CONTRIBUTING TO 40-55 KT OF EFFECTIVE BULK
SHEAR...ORGANIZED/SUSTAINED STORMS WITH SVR HAIL/WIND WILL BE
POSSIBLE.

..COHEN/CORFIDI.. 04/24/2014

[ou48A]

Sig Tor is a product that's been around awhile. I've linked it in the past as it is also available from some of the model runs. It usually holds some weight in paying attention, but it also needs to be used in conjunction with what is actually going on. The version you link for example. It shows a pretty focused area and moderate/high SIGTOR values over SW OK early this morning at about 4AM. Of course - there wasn't any tornadic weather at that time. We really need to have other factors line up for SIGTOR to be worth anyone's time. If there is on going storms at the time, or storms are expected to form, and other conditions are favorable for convective development - then we would look at SIGTOR to get an idea on tornado potential and risk for a strong tornado. It is also important to watch the time stamps of the forecast. Anytime after dark and through the morning hours will normally showcase moderate SIGTOR values just because it is when we normally have higher shear and helicity values. While CAPE, CIN, and LCL height are factors in the equation so is bulk wind shear and storm relative helicity. Those last two can make things look worse than they are. Now. Last year during the May tornadoes, we did have higher SIGTOR values during convective activity so it lined up and actually meant something.

For those that want to see the math: Significant Tornado Parameter (STP)

Sig Tor (CIN) = (mlCAPE / 1500 J/kg) * (ESRH / 150 m2/s2) * (EBWD / 12 m/s) * ((2000 - mlLCL) / 1000) * ((mlCINH + 200) / 150)

Thanks for your explanation....
The vast majority of us still understand we are still dealing with something that is inexact and can change very quickly....
That's one reason why I don't mine informed WX dissenting opinions.
I feel most of us are smart enough (or should be) to make good WX decisions for our own life’s.

[venture]

Not related to this weekend, but longer range there has been consistent hint of another round of active weather coming in around May 3rd through at least the 9th. Not every day...but that period of time.

[Ginkasa]

May 3rd

[Plutonic Panda]

Not related to this weekend, but longer range there has been consistent hint of another round of active weather coming in around May 3rd through at least the 9th. Not every day...but that period of time.

I'm telling you, if another EF5 goes through Moore on May 3rd, that place is cursed and needs to be vacated

[Roger S]

I'm telling you, if another EF5 goes through Moore on May 3rd, that place is cursed and needs to be vacated

I dare one to even try.... I'll be standing on my back porch with my putter in my hand ready to strike it down!

Edit: Oops... Just realized I'll be in Ardmore that weekend with a fishing rod in my hand..... Moore will have to fend for itself.

[Dessert Fox]

Although it doesn't mean much, KOCO's tornado scale rates western oklahomas chance at a 4/10 and the Metro at a 2/10

[LocoAko]

https://www.youtube.com/watch?v=30xt2lHCPyI

[Plutonic Panda]

I dare one to even try.... I'll be standing on my back porch with my putter in my hand ready to strike it down!

Edit: Oops... Just realized I'll be in Ardmore that weekend with a fishing rod in my hand..... Moore will have to fend for itself.

Maybe someone could get drunk and run up to it naked, with a bottle of whiskey like Bill did and scream ''HAVE A DRINK''

[PennyQuilts]

Not related to this weekend, but longer range there has been consistent hint of another round of active weather coming in around May 3rd through at least the 9th. Not every day...but that period of time.

Chris just swooned!!! (I kid, I kid). If we get tornado attack during that time, there are going to be people so freaked out he's going to be the one telling them to calm down.

[jn1780]

You know eventually were going to run out of days in May that is not associated with some kind of historical tornado event. lol

[PennyQuilts]

Seriously? Someone on FB just sent this to me!!

Forecasters Are Already Predicting a Massive Tornado Outbreak This Weekend

[s00nr1]

Everyone needs to chill out a bit in regards to this weekend.....things are far from certain for the metro and at this point I don't see anything near the magnitude of last May in the cards.

[PennyQuilts]

I read the article thinking it would tone down the eye catching headline but it was just as bad. I even looked at the NWS site to see if they were saying it was going to be severe on top of severe and didn't see that. I wanted to be nice to the lady who sent it to me because I appreciate that she cares. But with that sort of thing going on, half my friends and family are going to be convinced I am in the grim reaper's crosshairs.

[Klop]

Although it doesn't mean much, KOCO's tornado scale rates western oklahomas chance at a 4/10 and the Metro at a 2/10

Dessert Fox, this is in no way directed at you, more aimed the mainstream weather. When we have a chance of rain, its 40% and 20%. But, when we have a chance of tornadoes, its 4/10 and 2/10???? Most of us can do some basic math.

[SoonerDave]

I read the article thinking it would tone down the eye catching headline but it was just as bad. I even looked at the NWS site to see if they were saying it was going to be severe on top of severe and didn't see that. I wanted to be nice to the lady who sent it to me because I appreciate that she cares. But with that sort of thing going on, half my friends and family are going to be convinced I am in the grim reaper's crosshairs.

Venture can and obviously will correct me if I'm misreading this, but the most recent severe outlook for OK on Saturday doesn't look *nearly* as ominous as many were suggesting earlier this week. Some of the earlier forecasts were suggesting ridiculously high instability (something like 4K+ CAPE values) with big moisture return and dewpoints into the 70's, but it looks (again, assuming I'm reading the outlook correctly), initiation may form in a much narrower region of much lower (but still respectable) CAPE and lower dewpoints. Mind you, there's still a severe threat there, but it isn't nearly as grim.

Bottom line: Heed Venture when he warns us all not to take the long range outlooks as carved in stone. They're just that - outlooks based on mathematical models and a great deal of intuition, and maybe some cold pizza and oregano

[Uncle Slayton]

With the appropriate sensitivities considered, I have this sinking feeling that the big show is going to pass central OK by this time through.

[zookeeper]

Bottom line: Heed Venture when he warns us all not to take the long range outlooks as carved in stone. They're just that - outlooks based on mathematical models and a great deal of intuition, and maybe some cold pizza and oregano

And these days, maybe defining "oregano" loosely.