PWO for MDT risk days?

I have noticed a few instances in the past where the SPC has issued a Public Severe Weather Outlook, yet never upgraded the categorical convective outlook risk beyond Moderate. A couple of examples are June 08, 1995 (Pampa, Allison, Kellerville, TX), and October 04, 1998 (Oklahoma October Outbreak). In the SPC's ZIP files of archived products, the 6-5-95 convective outlooks include the wording "a public severe weather outlook will be issued shortly" but none of them go to high risk. Likewise for 10-04-98. Eric Nguyen's page even has both archived PWOs from that day. http://www.mesoscale.ws/98~documents/#981004

Does the SPC still do this? I wonder what the criteria are seeing as there are many MDT risk days on which PWOs are never issued.
 
I, for one, would hope SPC wouldn't refrain from putting out a PWO when they think they should.

Kind of a qualitative vs. quantitative kind of think.

I am curious as to what policy is in place.

mp
 
I'm not so much saying SPC should refrain from issuing a PWO if they feel it is necessary, but rather wondering why if they feel a PWO is necessary why they then don't also upgrade to high risk? Don't the two kind of go hand in hand as ways to emphasize a dangerous outbreak situation?
 
Here's what SPC says:

The Public Severe Weather Outlooks (PWO) are issued when a potentially significant or widespread tornado outbreak is expected. This plain-language forecast is typically issued 12-24 hours prior to the event and is used to alert NWS field offices and other weather customers concerned with public safety of a rare, dangerous situation. The PWO is reserved for only the most serious weather situations where a HIGH risk is forecast for a potential tornado outbreak. The SPC issues around 5 PWO's each year.
 
Here's what SPC says:

The Public Severe Weather Outlooks (PWO) are issued when a potentially significant or widespread tornado outbreak is expected. This plain-language forecast is typically issued 12-24 hours prior to the event and is used to alert NWS field offices and other weather customers concerned with public safety of a rare, dangerous situation. The PWO is reserved for only the most serious weather situations where a HIGH risk is forecast for a potential tornado outbreak. The SPC issues around 5 PWO's each year.

Well, my guess is they will issue a PWO on a MDT risk day that has the potential for being very widespread... I think we are getting mixed up with "probability" and "coverage"... A very small HIGH risk area (a very small portion of a state) may not warrant a PWO, whereas a MDT risk spanning several states just might fit the bill...
 
I think what you are saying _should_ be the case, but it's clear (capital letters and all) that a HIGH risk needs to be in place or SPC won't issue one.

Here's the exact wording from their directives:

5.3.3 Content. SPC will issue a Public Severe Weather Outlook when it forecasts any of the following conditions:

a. High risk of severe thunderstorms in the Categorical Day One Outlook;

b. 25% or greater probability of tornadoes, and a forecast of a 10% or greater probability of tornadoes which could cause F2 or greater damage within this area; or

c. 45% or greater probabilities of convective damaging wind gusts in conjunction with a 10% chance or 65 knot or greater wind gusts.

If a High Risk is initiated on the 0600 UTC Day 1 Outlook, a PWO will be issued at approximately 1000 and 1700 UTC. If the High Risk is initialized at 1300 a PWO will be issued at 1300 and 1700 UTC. A PWO may also be written around 2000 UTC for a high risk that is expected to occur during the overnight hours.
 
John Hart:

Our guidelines for PWOs have changed over the past few years. There
was a period (1993-1997) when we issued PWOs for high-end MDT risk
days. However, for the last several years, we have not done that.
Our current guidelines specify only issuing a PWO when a HIGH risk has
been issued. PWOs are issued so rarely that we often wonder about the
distribution and/or receipt of the product.
 
LOL Yep... probably the latter, though the current PSWO is incorrectly-formatted, which still makes me suspicious that they were debating about making it /sending it out, but sent it prematurely and/or accidentally.

I would think that the a PSWO would be issue if they were forecasting :

+ WIDESPREAD severe with damaging winds or very large hail
+ Scattered/isolated SIGNIFICANT strong/violent tornadoes

So, it's a case of numerous middle-end events, or at least scattered high-end events (strong/violent tornadoes, very damaging winds, etc). I think some of this may be SLIGHTLY political with metro areas possibly at risk (Tulsa, Springfield, Kansas City it appears in this case), but I don't want to make it sound like I think SPC folks let that stand in their way of outlooking objectively. This was brought up last year regarding whether population density (which, given a set area, would determine the number of people at risk) should be considered when issuing a high risk.

Anyways, I think they are anticipating widespread moderate-level severe, thus the issuance of a PSWO (despite that I'm still questioning the legitimacy of the PSWO given the atypical formattting)...
 
Interesting to see the discussion about this in Target Area...some are predicting an upgrade to high risk while others think the moderate risk/15% tornado prob will be removed.

My opinion regarding the PSWO is that it should be reserved for high risk days with an outbreak of strong/violent tornadoes anticipated (25% or 35% tornado probability with hatching) or an extreme derecho (45% hatched damaging wind).
 
LOL Yep... probably the latter, though the current PSWO is incorrectly-formatted, which still makes me suspicious that they were debating about making it /sending it out, but sent it prematurely and/or accidentally.

I would think that the a PSWO would be issue if they were forecasting :

+ WIDESPREAD severe with damaging winds or very large hail
+ Scattered/isolated SIGNIFICANT strong/violent tornadoes

So, it's a case of numerous middle-end events, or at least scattered high-end events (strong/violent tornadoes, very damaging winds, etc). I think some of this may be SLIGHTLY political with metro areas possibly at risk (Tulsa, Springfield, Kansas City it appears in this case), but I don't want to make it sound like I think SPC folks let that stand in their way of outlooking objectively. This was brought up last year regarding whether population density (which, given a set area, would determine the number of people at risk) should be considered when issuing a high risk.

Anyways, I think they are anticipating widespread moderate-level severe, thus the issuance of a PSWO (despite that I'm still questioning the legitimacy of the PSWO given the atypical formattting)...


Intesting thing happend....refreshed the SPC page. the PWO was gone. nowhere to be found.... This leads me to the conlusion it must have been some kind of error.
 
Andy -

It likely means that any severe weather encountered will be high-end severe, but the chances of actually encountering that severe weather are only MODERATE.

KR

EDIT: Although, after reading more of the posts on this thread, I would agree that I was fairly surprised to see the PSWO issued this morning.....I wasn't really expecting it and I DON'T know if it is really warranted.......maybe the button was pushed prematurely......we'll see.
 
pswo

The way the PSWO this morning was written, it looked like something they had written up just-in-case and was accidently sent out prematurely.
 
It looked like an accident to me too - and based on John Hart's comments - it looks like they may have indeed hit the send button by accident - and then had no choice but to make it legitimate and resend a corrected version. Hey, nobody is perfect.

Glen
 
The Public Severe Weather Outlooks (PWO) are issued when a potentially significant or widespread tornado outbreak is expected. This plain-language forecast is typically issued 12-24 hours prior to the event and is used to alert NWS field offices and other weather customers concerned with public safety of a rare, dangerous situation. The PWO is reserved for only the most serious weather situations where a HIGH risk is forecast for a potential tornado outbreak.

Well apparently the rules have been changed, because after deleting the initial PSWO they replaced it with a corrected one and did not upgrade to HIGH. They have also changed the wording on their PSWO "header" from

[Broken External Image]:http://sphs.angeltowns.net/images/pwo.gif

The SPC is forecasting an outbreak of severe thunderstorms today and tonight across portions of the United States. THIS IS AN EXTREMELY DANGEROUS SITUATION! Please read the latest public statement about this event.

To:

[Broken External Image]:http://sphs.angeltowns.net/images/pwo.gif

The SPC is forecasting an enhanced risk of severe thunderstorms today and tonight across portions of the United States. Please read the latest public statement about this event.

This does imply the difference in the percieved threat level, but I still think the PSWO should be reserved for those situations where the forecaster is thinking "this will be one for the severe weather history books". We might now see the PSWO become a near-routine product, given that moderate risks are far more common than high risks. While there are many noteable severe weather events that have occured on moderate risk days, most pass without any such major events. This is why I disagree with SPC's decision to once again issue PSWOs without a high risk as they did in the mid 1990s.
 
Because PWOs were *such* rare products (HIGH risk only, 3-4 times a year) they generally got little notice outside this sort of group (weather weenies who check for them specifically). PWOs were too rare!

Also, the technical SWOs are intended for meteorological guidance, not everybody at large. We get a LOT of feedback questions asking what CAPE means, what "30 NW END...RSL...TOP...25 N MKC" stand for, what is "deep layer shear", etc. Clearly there are a lot of folks trying to use the daily technical outlooks who don't (and shouldn't be expected to) understand them. This screams at the need for more frequent plain language products to convey the severe threat to more taxpayers. Yet we still wanted to reserve the PWO for only a most-critical subset of severe days that could be more dangerous than usual. Therefore...

Last winter I proposed increasing their frequency to all categorical MDTs in order to
1. Provide a plain language outlook (PWO) more often, explaining what the SPC forecasters expect on the days of heightened severe potential -- which are MDT and HIGH categorical risks (lately, 30-40 total/year on average)
2. Increase the visibility of SPC to the media and public through such outlooks.

Consensus among the staff was that it was worth a try, so we went with it -- a little later than hoped because one of the folks involved with software setup was out for a couple of months with medical problems. We also bumped down by one level a few of the probability thresholds for MDT risks. The various pages explaining these things should be updated soon, I hope.
 
Originally posted by Roger Edwards
Because PWOs were *such* rare products (HIGH risk only, 3-4 times a year) they generally got little notice outside this sort of group (weather weenies who check for them specifically). PWOs were too rare!

Also, the technical SWOs are intended for meteorological guidance, not everybody at large. We get a LOT of feedback questions asking what CAPE means, what \"30 NW END...RSL...TOP...25 N MKC\" stand for, what is \"deep layer shear\", etc. Clearly there are a lot of folks trying to use the daily technical outlooks who don't (and shouldn't be expected to) understand them. This screams at the need for more frequent plain language products to convey the severe threat to more taxpayers. Yet we still wanted to reserve the PWO for only a most-critical subset of severe days that could be more dangerous than usual. Therefore...

Last winter I proposed increasing their frequency to all categorical MDTs in order to
1. Provide a plain language outlook (PWO) more often, explaining what the SPC forecasters expect on the days of heightened severe potential -- which are MDT and HIGH categorical risks (lately, 30-40 total/year on average)
2. Increase the visibility of SPC to the media and public through such outlooks.

Consensus among the staff was that it was worth a try, so we went with it -- a little later than hoped because one of the folks involved with software setup was out for a couple of months with medical problems. We also bumped down by one level a few of the probability thresholds for MDT risks. The various pages explaining these things should be updated soon, I hope.

Sounds very reasonable to me...

There we have it guys, official word from SPC!
 
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