Tuesday, July 17, 2012

Dubious Heat Advisories

In a season when heat advisories and excessive heat warnings are making regular appearances in Twin Cities forecasting lexicon, we’re starting to wonder whether they serve much purpose or at least question the proper use of them. A comparison of today’s weather with yesterday’s provides a good example.

On Monday, the Twin Cities was under a heat advisory. The temperature reached 98 degrees but the humidity was only moderate, and the heat index never reached advisory levels. And while it doesn’t figure in to the formal mathematical calculation of heat index, a persistent, gusty southwest wind made the heat more tolerable than it might otherwise have been.

In contrast, today’s high temperature reached 94 but the humidity was more oppressive. Toss in light and variable winds and it’s fair to say that most people would think today was more uncomfortable. The NWS did not issue a heat advisory and the heat index technically touched advisory levels (100). On June 27, a formal heat advisory was issued, yet the heat index never reached 100.

With the benefit of hindsight, an advisory (technically) should have been issued for Tuesday rather than Monday. And when you throw in the ill-advised heat advisory on June 27, that’s three days where the issuance/nonissuance of an advisory was wrong. To us, this merely points up the dubious nature of the formality of heat advisories in the first place. Throw in the oddly worded “excessive heat warning” and you’ve got even more confusion.

It’s simply very hot and uncomfortable weather! Nothing more, nothing less. In our minds, the advisories and warnings that occur in winter have far more relevance and significance to our daily lives. If the windchill is a gazillion degrees below zero and you take a long walk without being properly dressed, you’re going to suffer frostbite at a minimum and you could potentially freeze to death. If heavy snow arrives, particularly during rush hour, it’s going to mess with your commute and you might need to plan accordingly. But if the heat index one day is 100 and another day is 98, is that really much of a meaningful difference? And more importantly, is one day more worthy of a heat advisory than the other? We think not.

If you're curious to see official definitions for advisories, warnings, watches and the like for the Twin Cities, click here.

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32 comments:

  1. I do not understand why the NWS does not treat heat advisories/warnings like severe thunderstorm warnings. You monitor the situation and if a severe thunderstorm develop you issue a warning. Likewise you monitor the heat index and if conditions warrant you issue it.
    Like they issue a severe thunderstorm or tornado watch if conditions are favorable, they could issue a heat weather watch if conditions are favorable,but ONLY issue a warning or advisory if really needed.
    It seems plain and simple to me.

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    1. I believe they sometimes issue Excessive Heat Watches but don't issue "advisory watches." Also, whether an advisory is justified is not always known until after the fact. If they issue an advisory for expected heat indexes of 100 to 110 and the peak index is only 98 or 99, well then it was a blown forecast. The problem is that heat is not an instantaneous thing like a thunderstorm or tornado but rather a long-duration event lasting several hours. I still think the general public is rather clueless about advisories and warnings related to heat, which is why I question their value.

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  2. It is not "simply" hot and uncomfortable weather. There are serious threats to health and welfare when the temperature gets so warm, especially to the elderly, those with certain medical conditions, or those who are outside. A heat advisory or other heat-related watch/warning/advisory tells people that this isn't "just" hot weather - it notifies them that they need to take extra precautions, stay inside if possible or only go out for short periods of time, drink extra fluids, and be more alert to heat-related health concerns. Advance notice gives people without air conditioning a heads' up that they may want to find a friend with air conditioning to stay with, or that their health condition(s) may be exacerbated within the next few days.

    Re your comment of heat index forecast of 100-110* and it only hitting 98* being a bust - that is simply not true. Forecasting is not something that can be pinpointed exactly. There are too many variables for forecasters to say, with 100% certainty, that the weather tomorrow will be sunny with a high temperature of exactly 76* and a low temperature of exactly 56*. Temperature can vary from your front yard to back yard. Take the temperature in your front yard, where there are no trees, and your temperature might be at the forecasted number. Take the temperature in your shady backyard, and it might be five degrees cooler. Does that mean the forecast was a bust? No. If the forecast was for 100-110* and the heat index only hit 80, that is a blown forecast. Again, the weather is not something that can forecasted down to the exact degree. To tear apart the NWS and/or forecasters because the temperature or heat index was 2* above/below the forecast shows a lack of understanding of forecasting and makes you look ignorant and uneducated. It is okay to be uneducated, but if you don't understand something the appropriate response is to seek understanding, not tell the people with more knowledge that they're idiots. If I started tearing your profession apart, with little understanding of the details and nuances of that field, you would think I was an idiot, roll your eyes at me, and laugh at my ignorance. Yet you have created an entire blog around tearing apart an industry that you are not trained in.

    If the general public is clueless about something, then there needs to be more education. Simply getting rid of the thing the general public is clueless about is ridiculous. The general public doesn't often understand why doctors order certain tests or prescribe certain medications. Should we tell doctors to stop doing those things because people don't understand them. People don't understand everything a lawyer does, or why lawyers need to follow certain procedures. Should we do away with laywers? Education is the answer, not getting rid of tests, procedures, or warnings/watches/advisories.

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    1. @Pam Thanks for taking the time to post such a well thought-out, articulate response. You make some good points.

      I would take exception to the idea this blog is devoted to tearing down an industry. I can see how you might come to that conclusion based on the recent entries regarding heat advisories, but the general idea is to compare forecaster performance and even provide features of various forecasters. We also provide reviews of weather apps and ask the NWS for answers to questions in some cases (see also: http://www.minnesotaforecaster.com/2012/06/tornado-or-straight-line-winds-when.html).

      Perhaps it's useful for me to remember that the NWS is the only forecaster allowed to assert watches and warnings, which they are doing from a public safety perspective, and that that means they have more to be evaluated on than television stations that merely provide temp and precip forecasts. I may forget the public safety aspect and think more along forecast assessment as a kind of sport.

      I grew up in an area where summers were more similar to what Minneapolis is experiencing this summer, and in a time when heat advisories and watches did not exist. A forecast of "hot and humid with a high of 96" told us all we needed to know and we used common sense, a commodity that sometimes seems more scarce in today's world.

      Again, thank you for your input, and please feel free to share your views in the future.

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  3. Also. to further Pam's points are that the forecasts and the advisories/watches/warnings based on these are for more than just discrete points such as in the example of the Twin Cities Intl Airport observation point of KMSP. The June 27 heat advisory upon looking back was not ill-advised and was an excellent one for over 97% of the area it was issued to cover. Because parts, but not all of the Twin Cities did not hit the 100F value but rather 98F or 99F definitely backed the advisory given the situation at hand. Think of a Severe Thunderstorm Watch issued over numerous counties. Then a Severe Thunderstorm Warning for a segment of a county. That does not mean every square mile warned will definitely experience severe thunderstorms conditions (58+ mph winds or 1" or greater hail size), however, the probabilities of such to occur are fairly high based on radar signatures, reports and history of a storm. So when a section of west St. Paul is hit but the rest of the city is fairly free of damage that does not constitute a bust, either despite being in the polygonal warning issued. The probability of damage was just as high but luckily didn't happen for all areas.

    Regarding, Heat Advisories vs Excessive Heat Warning -- yes, there are definitely no perfect ways to word weather event 'alerts' but plenty of work and research has been done and in definitely progress which is now including social scientists on how to better NWS 'alerts' for the public. By the way, my friends at the Natl Hurricane Center do a nice presentation on this topic as many years ago Alerts were issued and people were very confused and thus TS and Hurricane Watches and Warnings were born from this problem in the 40s/50s. History sometimes needs to be addressed in this world including weather and climate's own past which is pretty interesting in itself.

    *One final note from a statistic seen last week that there have been 5 heat-related deaths in western Wisconsin, but fortunately none reported in Minnesota. But, this does not take into account the numerous incidences of heat-related exhaustion and stroke victims admitted to doctor offices, urgent care clinics and hospital. (These data are available in time as I have seen the CDC use these in the past.)

    Also, private forecast companies do issue heat-related type of forecasts and similar advisories for their clients so it is definitely more than the NWS that is responsible for advising people and industry of the weather situation whether it be heat, cold, snow, ice, blizzards, severe weather, hurricanes and fire weather to name a few.

    Hopefully, that helps and gives some additional insight to wide world of weather advisories/watches/warnings.

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    1. @DDwx Thanks for the additional information and clarification!

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  4. What's anybody's outlook for the remainder of the summer? We've been in an extremely boring patten for many weeks. Any chance for a change?

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    1. I'm curious if anybody has any preliminary thoughts on the setup for this weekend (8/3-8/4).

      In my admittedly limited knowledge, it looks and sounds (from SPC and MPX forecast discission) that something big will happen somewhere this weekend and it may be here.

      Does anybody have any thoughts on it yet? I know the timing of the front will be the largest determining factor, just kinda wondering what the odds are at this point...

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    2. @ disco- looks like an active set up for this week.

      @-Neil- I'd be more worried about today than this weekend right now. the weekend storm looks like it might simply skip over us.

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  5. Major league busted forecast yesterday. Twin Cities were right in the middle of SLGT risk and even had a severe thunderstorm watch in the early evening. I didn't get a drop of rain at my place.

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    1. I don't know if that was really a bust or not. I think the watch and slight risk designation only mean that conditions are ripe for t-storms, not that they're actually predicting it. That said, there was a 60% chance of rain if I recall correctly and none occurred here at TMF headquarters.

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    2. 60% chance of rain is still a 40% chance it won't rain. Sounds like a good forecast to me.

      --Kevin.

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  6. 6 of the past 14 months in the Twin Cities are in the top ten warmest for those respective months. That is incredible to me. The last two Julys have been the 2nd warmest (2012) and 6th warmest (2011) on record.

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  7. Plymouth Weather LoverAugust 6, 2012 at 12:00 AM

    Snow??

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    1. The cpc forecasts a winter similar to last winter. Otherwise, it is WAY too far out to tell.


      http://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=4

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    2. Upcoming winter update from weather.com:

      http://www.weather.com/news/long-term-pattern-cooler-20120813

      It looks cold,perhaps snowy, but it is still in question.

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  8. Considerable coolness coming......60's for highs and 40's for lows...........free AC!,after such a hot summer,this is a good welcome change,fall isn't too far behind

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  9. Right smack dab in the middle of SLGT and it appears they've canceled the watch. Wow. Another big-time bust.

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    1. Huttner this morning was predicting bow echoes!

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  10. @Disco80....it was such a big-time double bust.....it rained(hard) and much more yesterday morning(when no one predicted anything)then last night,when all the hype/forecast was for heavy rain with hail and damaging winds being the severe threat..........but I love this cool air after the front though,have all the windows open,even tonight when we dip into the 40's.

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  11. I also thought Tuesday's clouds and evening rain came ahead of schedule. It was a tough little two-day stretch for our mets.

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  12. Nice write up on MPX getting their first chance to use dual pol radar that was installed last week.

    http://www.crh.noaa.gov/images/mpx/081512StevensHail.pdf

    Looking forward to seeing it in action this winter.

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  13. I hope to have my forecast set for the entire run of the state fair by Sunday as I have that day off, I have been looking at some thing's and right now I'm thinking above normal high temps with near normal lows.

    Bill, it might be interesting to start a new thread dealing with the State Fair forecast, if you are so inclined to do so.

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  14. My forecast for the first weekend of the State Fair

    First of all let me say this, the Dew Points predicted by the GFS are so high they are almost laughable, and that impacts the predicted highs for that model. High temps should be much higher than predicted.

    Dews from the GFS: http://www.meteor.iastate.edu/~ckarsten/bufkit/images/plotter.php?site=kmsp&var=td&nam=1&namm=1&gfs=1&gfsm=1&rap=1&nam_mos=1&gfs_mos=1&gfsm_mos=1&nws=1&obs=1&con=1

    Temps from the GFS: http://www.meteor.iastate.edu/~ckarsten/bufkit/images/plotter.php?site=kmsp&var=tf&nam=1&namm=1&gfs=1&gfsm=1&rap=1&nam_mos=1&gfs_mos=1&gfsm_mos=1&nws=1&obs=1&con=1

    Notice the trend of the Nam model while looking at this, the dews are a little low in my opinion, thus the temps a bit higher.

    Thursday: High temp 87°. Dew Point around 60° Change of rain after 7pm 40%, would like to go higher with the rain chances as both the GFS and Euro show that, but this far out 40% is all I feel comfortable with.

    Friday: High temp 86° Dew Point around 65° scattered showers are possible in the am through late afternoon, clearing up after that.

    Saturday: High temp around 86° Dew point around 65° rain chances 20% (Euro show none)

    Sunday High temp around 75° Dew point around 65°, this looks like the best chance for rain at the fair grounds throughout the day.

    Monday High Temp around 78° with Dew points around 53° rain chances around 20%

    Best day for the 1st weekend looks like Saturday.

    After that it looks like equal chances of below or slightly above normal temps as the models diverge greatly

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    1. also keeping a eye on the Caribbean and the Gulf...While chances are low, say 20-30%, there is chance we could see a spike in gas prices if a Tropical Storm impacts the off shore drilling sites in the Gulf

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    2. @Randy,your efforts at best was 50/50 for your fair forecast,but that's just as reliable as our local mets,so you can take some solace from that,but at least you tried.....Thursday/Friday was pretty much spot on,with only a 1-3 degree variance.....Saturday/Sunday you got the temps reversed with hardly any rain,especially Sunday,your temp looks abit low for today(they should easily warm into the mid 80's).As far as the rest of the week goes,it will be pretty much dry and well above normal temp(not slightly)I could see a string of 5+ days at or above 90,good efforts on seeing Issac coming,any other tropical cyclones on the horizon?

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  15. This ought to be an interesting week to see how the forecasts perform. Today's forecast high is 90. As of 12.53pm, because of cloud cover, the temp was only 79. Likely bust.

    There's an "excessive heat watch" for Thursday -- with a forecast high of 90. A heat watch for 90 degrees. With a forecast of 95 on Wednesday, there's no heat watch.

    Confused.

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  16. What a forecast by NHC. Pretty close on track and nailed intensity 5 days out.

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    1. Agree on intensity, but I thought they were originally thinking it would hit near central Florida. I'd like to see a track/cone from five days ago. My sense was that it went to the western part of the cone at every turn.

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    2. For the final 5 days, the eventual landfall point was in the cone for all but one or two advisories three days out.

      Considering that forecasts will go outside the cone 1/3rd of the time, it was actually a pretty good forcast.

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  17. @Bill you are correct,at every turn Issac went to the western part of the cone,even as late as Sunday afternoon NHC had the center of Issac over the Florida panhandle,so in about 48 hours time it drifted west,there is an excellent graphic depicting the uncertainity cone of Issac since it became an TS,just go to NWS homepage,click on the Issac info,find the archives on that page,then go to 'Issac graghical archives' and it has everything,hope that helps.....@Disco80 not sure what forecast your looking at or why your confused over the Heat Watch,NWS has a high of 91 for WED,97 for Thur,and 92 Fri,accordingly for MSP!

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  18. Wunderground has Thursday's high at 93. The heat-watch-whatever looks like it's been cancelled.

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