One of the things that we Minnesotans are entitled yes ENTITLED to for enduring this place's ridiculous seven-month winters is sumptuously spectacular thunderstorms.

My usual source of weather forecast info is weather.gov. Usually they are pretty accurate about the upcoming temperature, clouds vs sunshine, etc.

But when it comes to predicting thunderstorms, they miss the mark and they miss it widely. Last Monday night there were supposed to be thunderstorms. I don't work Monday nights (when I do work I am three floors underground ) so I was severely looking forward to the weather, for all of the five yes FIVE DAYS that NWS had been telling us there was a 70% likelihood of thunderstorms that night. At no point during those five days did their website ever say the likelihood was anything less than 70%.

Late Monday afternoon/prevening arrived, and the local TV stations told us there would not be any thunderstorms, probably not even any rain, and indeed when I checked weather.gov it too was by then predicting a thunderstorm-free evening.

After FIVE DAYS of telling us there was a not-less-than 70% likelihood.

I would not be as furious about this as I am if it weren't for the fact that there was a time, now several years ago but I shan't forget it, when the same-night prediction was a 100% yes ONE HUNDRED PER CENT chance not just of thunderstorms, but of SEVERE thunderstorms... and throughout the night, nothing happened.

How can they be confident on one night that there's a 100% chance of storms later that night, when clearly that's not what was queued up to happen...

How could they have stayed confident for five consecutive days that there was a 70% chance of storms, when in fact no storms at all would happen (not even a little bit )....






I require my thunderstorms.

70% chance is like two-third. There are two-third chance that there will be storms and so there are one-third chance that there won't be any storms. It mean every one out of three tine when they make a 70% prediction they result would be different.
As for 100% prediction later the date, it probably is something rounded up from 95% or so. I don't think current knowledge of humanity knowledge would enable 100% prediction accuracy. You can look at radar see a cloud of storm coming, but just before they come to your location they split up and vanish, that's something that would happen rather frequently.

Where are you in MN? When I lived in STL I had the same issue: NWS predicting high chance of rain/tstorms only for them to fizzle out shortly before reaching the metro area and regaining strength once in IL.

Depending on where you are, my guess is the urban heat island effect. Even though added heat is beneficial to thunderstorms, the temperature gradient as it enters the zone may make the air turbulent, which may explain why storms sometimes fizzle out. Downwind, however, air is stable once more and allows for that warm, humid air to condense again. The other thing to consider is how the jet stream is behaving. Earlier this week, North Dakota was a prime area for severe weather. If the jet stream did not dip south and just stayed north (contrary to forecasts), that's the path the storms will follow. So northern MN probably saw some weather.

As for probability of rain, the number is composed of the product of two items:
1. A confidence number C (0-1)
2. Area coverage A (0-1).

If a forecaster is 100% confident that there will be rain, C=1. It comes down to what area coverage gets rain. If the forecaster believes 40% of the coverage area will see rain, A=0.4, so there's a 40% chance of measurable rain in the forecast area.

If the forecaster is only 60% certain, then 0.6*0.4=.24 = 20-30% chance of rain.

FWIW, I lived in the Twin Cities area from 83-96 while working for a certain airline which had a red tail. I thought the NWS did a very respectable job of forecasting the extremes of summer and winter weather. I think there is a certain bias toward being overly pessimistic when predicting TRWs. Better safe than sorry so to speak.

No one said you have to live in Americas Siberia.

I think summer thunderstorms are inherently volatile and difficult to predict. They know it will be hot and humid... guess what? Enormous convections of hot/cold material with a lot of sun energy do unpredictable things. It can fizzle or it can really go boom. With that much potential energy, big stuff can happen quickly. Or not.

8:30pm CDT and here is the view out my window (the skyscraper in the distance is Minneapolis's IDS Center).

http://imgur.com/CVugsdu


They're still saying 80% chance of thunderstorms; does it look like it?

I only listen to Cantore the dude is baller

And another thing...

When I logged on to weather.gov earlier today it said the current temperature ici in Minneapolis was 98°F. It also said the forecast called for a high of 94°F.

How do they with a clear conscience continue to report that 94 is the predicted high when THEIR OWN DATA disproves that?!?!??!?

Airstud wrote:

8:30pm CDT and here is the view out my window (the skyscraper in the distance is Minneapolis's IDS Center).

http://imgur.com/CVugsdu


They're still saying 80% chance of thunderstorms; does it look like it?

Those look like there will be storms over the Blue and Wallowa Mountains later, if those same clouds were in Oregon. But, the prairie? I don't have that experience.

Airstud wrote:

And another thing...

When I logged on to weather.gov earlier today it said the current temperature ici in Minneapolis was 98°F. It also said the forecast called for a high of 94°F.

How do they with a clear conscience continue to report that 94 is the predicted high when THEIR OWN DATA disproves that?!?!??!?

That bugs me, too.

Here in OTH, the NWS has been predicting a high of 67 and sun for the past two weeks. The airport has not gotten above 65 since January 1. And, being right on the ocean, it is clouds and fog all the time. When I lived in PDX, there were days when NWS said "thunderstorms and 75" but, it was clear all day and over 85.

I was very young when I learned to never trust the weatherman....

Airstud wrote:

How do they with a clear conscience continue to report that 94 is the predicted high when THEIR OWN DATA disproves that?!?!??!?

Once the stop doing forecasts, maybe an hour before now, the forecast value doesn't change anymore. No reason to hide the fact that it was 4° off.
Also the actual temperature is a point temperature, or an average of several points, the forecast is for a whole grid square.

Best regards
Thomas

Airstud wrote:

How could they have stayed confident for five consecutive days that there was a 70% chance of storms, when in fact no storms at all would happen (not even a little bit )....

You grew up in New England, but you require correct weather forecasts??

Airstud wrote:

there was a time

...when I was so broken-hearted...

tommy1808 wrote:

Once they stop doing forecasts, maybe an hour before now, the forecast value doesn't change anymore. No reason to hide the fact that it was 4° off.
Also the actual temperature is a point temperature, or an average of several points, the forecast is for a whole grid square.

Which, is what I said basically.

tommy1808 wrote:

Also the actual temperature is a point temperature, or an average of several points, the forecast is for a whole grid square.

The temperature read is that of a single weather station. The other thing to note is that a forecast is just that: a forecast. Forecasts will never be 100% accurate.

Besides, can you really notice a 4 degree difference? Now, if you say there's a 10 degree difference (say 80 to 90), THAT'S a significant change.

vikkyvik wrote:

Airstud wrote:

How could they have stayed confident for five consecutive days that there was a 70% chance of storms, when in fact no storms at all would happen (not even a little bit )....

You grew up in New England, but you require correct weather forecasts??

I require my thunderstorms, is what I require. See opening post.




Tonight, they said they'd be here starting at 2am so already they're late.

Airstud wrote:

vikkyvik wrote:

Airstud wrote:

How could they have stayed confident for five consecutive days that there was a 70% chance of storms, when in fact no storms at all would happen (not even a little bit )....

You grew up in New England, but you require correct weather forecasts??

I require my thunderstorms, is what I require. See opening post.




Tonight, they said they'd be here starting at 2am so already they're late.

See also #2 post

You know, I have bone to pick with the NWS after all.

They said today was gonna be a sunny day. Their forecast chart clearly said sunny; not party cloudy, not fair skies, not mostly sunny...SUNNY. So why were there little white clouds isolated in the sky?

False advertisement!

The 70% chance means in actuality that in the forecast area, 70% of the area will have t-storms (or whatnot) un the given time. I t says nothing about your specific lat/long having a 70% chance of a storm occurring.

MarSciGuy wrote:

The 70% chance means in actuality that in the forecast area, 70% of the area will have t-storms (or whatnot) un the given time. I t says nothing about your specific lat/long having a 70% chance of a storm occurring.

I.

Require.

My.


THUNDERSTORMS !!!!!!!!!!

While you are deprived, here is an absolutely excellent 45 minute video on storm spotting technique, emphasis on visualization of supercell structure from the ground

https://youtu.be/bq0-QXXtOro

Do what my wife did who is from Minnesota; move to Kansas. They are extremely good at predicting thunderstorms here. Even better at predicting when tornado outbreaks will happen. So good in fact that when threats are elevated you usually see people leaving work early based on forecasted times.

Most people who live in Kansas (and I imagine the same is true for others in the lower plain states) are quite good at recognizing the right conditions for severe weather. I can look at a radar and tell you if there is a super cell is capable of producing a tornado almost instantly.

trpmb6 wrote:

I can look at a radar and tell you if there is a super cell is capable of producing a tornado almost instantly.

I can look at the spinning ground from my flying Toyota and tell you the same thing.

I'm near MSP on a chronic level. The last two nights of thunderstorm predictions were spot on. I gave up storm chasing and spotting a few years ago. Someone else can enjoy getting their vehicle dented by thunderstorm hail. Anyway, I like watching flight radar during thunderstorms near MSP. The usual 30 minute hop from MKE to MSP took the aircraft up to Canada and around the back side of the storms near BRD. And that folks, is how you make a 30 minute flight into a two hours nightmare. The fun part was watching the Menard corporate E135 (N538M) trying to make it from LSE to EAU. The guy flew at 2000 ft to AUW and then hung a left to EAU.... right through the storm.