Winter forecast, part II: NOAA's predicts a warm winter for the Central U.S.

By: Dr. Jeff Masters , 2:51 PM GMT on November 21, 2008

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Let's follow up on yesterday's discussion about the long range forecast for the coming United States winter. Those of you outside the U.S. will probably be more interested in what the International Research Institute for Climate Prediction has to say for your country, and I encourage you to check out their excellent web site for their seasonal forecasts.

The official National Oceanic and Atmospheric Administration (NOAA) 90-day forecast for the upcoming winter, issued on November 20 by their Climate Prediction Center (CPC), calls for above average temperatures across the Central U.S. and Alaska. The remainder of the country has equal chances of above or below average temperatures. A dryer than average winter is expected over much of the Southern U.S., including the drought-stricken Southeast U.S.


Figure 1. Temperature forecast for the upcoming winter--December, January, and February 2009--made by NOAA's Climate Prediction Center. No areas of the country ar forecast to have an above-average chance of being colder than normal, but the Central U.S. has up to a 50% chance of having above-average temperatures.

How are the NOAA winter forecasts made?
NOAA uses several tools to make their forecasts. One key tool is their Climate Forecast System (CFS) model. This model includes a version of the GFS forecast model that we use for everyday weather and hurricane track forecasts. The CFS model also includes an ocean model that interacts with the atmospheric model. These models solve mathematical equations of fluid flow using a supercomputer for the entire globe, on a 100-km grid. NOAA also uses statistical models, which look at past winters and see how they depended on quantities such as sea surface temperature anomalies. Temperature trends are important, too--if it has been warmer than average the last ten years, it's a good idea to forecast a warmer than average winter.


Figure 2. Skill of the official 90-day forecasts issued 0.5 months in advance by NOAA's Climate Prediction Center. Note that the average skill over the past ten years is not very high (9 on a scale of 0 to 100), and has remained flat, indicating that our skill in making long-range forecasts has not improved.

How good are the NOAA winter forecasts?
NOAA rates its forecasts using the Heidke skill score, which is a measure of how well a forecast did relative to a randomly selected forecast. A score of 0 means that the forecast did no better than what would be expected by chance. A score of 100 depicts a "perfect" forecast, and a score of -50 depicts the "worst possible" forecast. For 90-day temperature forecasts issued 0.5 months in advance, NOAA has averaged a 9 out of 100 on the Heidke scale since 1995 (Figure 2). So, while there is some skill in forecasting what winter temperatures will be like, this skill is not much better than flipping a coin. Depressingly, Heidke skill scores for three-month precipitation forecasts are even worse, averaging just a one on a scale of 1 to 100 over the past 15 years.

Let's look at some examples. Last's year's winter temperature forecast issued in mid-November did poorly (Figure 3), failing to forecast that the U.S. would have equal areas with both above and below average temperatures. The 90-day forecast done in mid-November of 2005 for the winter of 2005-2006 was awesome, with a Heidke skill score of 45. However, the 90-day forecast done in mid-November of 2006 for the winter of 2006-2007 had virtually no skill, with a Heidke skill score of one.



Figure 3. Temperature forecast for Dec 2007-Feb 2008 issued by NOAA's Climate Prediction Center on November 15, 2007 (top). They predicted Equal Chances (EC) of either above or below-average temperatures for the Northwestern U.S. (white colored areas), and a 30-60% chance of above average temperatures over most of the remainder of the country. In reality, the U.S. experienced an average winter, with approximately equal areas of the country receiving above and below average temperatures (bottom). Image credit: National Climatic Data Center.

Why do seasonal forecasts do so poorly? Primarily, it's because the long-term weather patterns are chaotic and fundamentally unpredictable. To a lesser degree, we are limited by our imperfect physical understanding of what controls the climate, and our imperfect computer models we use to simulate the climate. As computer power continues to increase and our models include better representations of the weather and climate at finer grid sizes, I anticipate that seasonal forecasts will improve. However, given that long-range forecasts have not improved since 1995 despite a large increase in computer power, I doubt that this improvement will be more than 10-20% over the next thirty years.

Seasonal forecast models vs. climate models
A common complaint one hears about global warming predictions made by climate models is, "How can we trust the predictions of these climate modes, when they so such a lousy job with seasonal forecasts?" It's a good question, and there is no doubt that seasonal forecasts have pretty marginal skill. However, there is a fundamental difference between making a seasonal forecast and making a 100-year climate forecast. A seasonal or a short-term weather forecast is what mathematicians call an "initial value" problem. One starts with a set of initial meteorological and oceanographic values that specify the initial state of the planet's weather, then solve the equations of fluid flow to arrive at the state of the atmosphere a few days, weeks, or months into the future. This forecast is highly sensitive to any imperfections one has in the initial conditions. Since there are large regions of the atmosphere and ocean we don't sample, it's guaranteed that the prediction will suffer significantly from imperfect initial conditions. Furthermore, the chaotic and turbulent nature of the atmosphere leads to many "bumps" in the weather pattern over time scales of days, weeks, and months. The nature of turbulence makes it impossible to accurately forecast these "bumps" that are superimposed on the mean state of the climate.

A 100-year climate forecast, on the other hand, is what mathematicians call a "boundary value" problem. Given an initial and final set of factors (called "forcings") that influence the climate, one runs a climate model 100 years into the future. The final state of the climate will depend on the strength of the forcings supplied. This type of model is not very sensitive to initial conditions, and is not trying to forecast the "bumps" of chaotic, turbulent atmospheric motion superimposed on the mean climate. Rather, one is trying to forecast the mean climate. As computer power increases and our physical understanding of how the climate works grows, these type of models will continue to significantly improve. While climate models do fail to properly simulate important aspects of our past climate, such as the Arctic warming of the 1930s, and the observed 0.1°C global temperature increase that occurs at the peak of the 11-year solar sunspot cycle, they have been very successful at simulating things like the global cooling triggered by the 1992 Mt. Pinatubo eruption, and the observed pattern of greatest global warming in the Arctic. I believe that climate models are already significantly more reliable than seasonal forecast models, and should continue to improve steadily in coming years.

Support the Portlight Christmas for Gulf Coast Kids Honor Walk
Saturday is the portlight.org Christmas for Gulf Coast Kids Honor Walk. This is a fundraiser to buy gifts for the kids along the Gulf Coast who might not have much in their stockings this year because of the ravages of Hurricane Ike. Our own StormJunkie will be walking up the Arthur Ravenel Jr. Bridge in Charleston, SC, and will be taking his webcam along. Tune in to the webcam site at 2:30 pm EST to follow the walk, and participate in a live chat. Sponsorships of any amount, small or large, are appreciated! The cam will go active about an hour before the walk. It should be a cold but beautiful day.

Jeff Masters

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Quoting Drakoen:


LOL. I can't stand Palin's voice. It feels so forced and sharp. Don't mind some gory turkey action lol.


mind you its from the huffington post...
Link

sounds exactly like something she would say, but she didn't
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Quoting BahaHurican:
Don't bother. It's a lot of yadayada from Palin and some gory turkey action in the background. As has been said ad infinitum, not a good choice of location, unless of course you WANT to shock the world. . . . kinda like snapping numerous pics of the alligater after the hurricane, then choosing the one where it's scarfing down someone's deceased pooch or kitty to post beside your news article on recovery efforts. . .


LOL. I can't stand Palin's voice. It feels so forced and sharp. Don't mind some gory turkey action lol.
Member Since: October 28, 2006 Posts: 57 Comments: 30559
I hold no brief for Ms. Palin. But I am sure that she had no idea what was going on over her shoulder in view of the camera.
I have had some experience with media, and the Cameraman must have been thinking "please dont turn around to see what I am showing the world here."
I do believe that the video is a breach of media "good faith". Or it should be.
An abuse of a situation by the media involved.
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Quoting Drakoen:


I didn't even look at the video sorry... lol.
Don't bother. It's a lot of yadayada from Palin and some gory turkey action in the background. As has been said ad infinitum, not a good choice of location, unless of course you WANT to shock the world. . . . kinda like snapping numerous pics of the alligater after the hurricane, then choosing the one where it's scarfing down someone's deceased pooch or kitty to post beside your news article on recovery efforts. . .
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Quoting CosmicEvents:
What are the chances that 96L will hit the OBX (NC) as a cat 2?


This made me laugh, as this can't be even remotely a serious question.

Regardless, the percentages of that actually happening are <.00000000001%.
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for the record...how old is drak?
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Quoting GeoffreyWPB:
Come on Drak...Sarah Palin pardoned a turkey...then in her post interview...turkies were killed behind her.....bad move publicity wise?


I didn't even look at the video sorry... lol.
Member Since: October 28, 2006 Posts: 57 Comments: 30559
Quoting Drakoen:


Well this season helped me learn a lot about everyone. I know whose real and whose fake in here. Things will be different next year... at least on my end.

No one in this blog has the power to run over me LOL!
I'm sure we'll have some more [new] real and fake people next season . . .. seems we get a new crop every year LOL

Actually this was a good teaching season in a lot of ways, not least because there were so many "unusual" or record-setting storms. Also the season's track trend was a rather unusual one. I don't think we have too many seasons where the high hung so far SW that everything for 6 - 10 weeks ran over the greater Antilles . . .
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Quoting CosmicEvents:
What are the chances that 96L will hit the OBX as a cat 2?


OBX???? If you mean north of Costa Rica, >1%
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That would indeed be very freaky, Baha.
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Come on Drak...Sarah Palin pardoned a turkey...then in her post interview...turkies were killed behind her.....bad move publicity wise?
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Quoting BahaHurican:
It would really be very interesting if we ended with Rene-Rachel, a ATL-EPAC crosser. Talk about ending as we began, only in reverse . . .


It's cyclic...
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Quoting Drakoen:


Well this season helped me learn a lot about everyone. I know whose real and whose fake in here. Things will be different next year... at least on my end.

No one in this blog has the power to run over me LOL!


I have believed you since 2006, but I still thought Dolly would form earlier... And I learned something. My writing and thinking style is apparently very similar to an unmentioned troll (not going to mention the name), and when I first got on here I had to dispel rumours. But I eventually came into a better light and I have new friends. Thank you. (sends hug to everyone)
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What are the chances that 96L will hit the OBX (NC) as a cat 2?
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It would really be very interesting if we ended with Rene-Rachel, a ATL-EPAC crosser. Talk about ending as we began, only in reverse . . .
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l just thought it ironic..since a pardon...but knows what happens in real life..thank you
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Quoting BahaHurican:
Surely have to in this blog, or u may just get run over. . . LOL

It was an interesting summer.

Interestingly enough, while many storms toasted our edges, and the SE part got fried, no storms actually ran right over us. Guess that means my 1926 / 1928 analog years were a bit off. . . .


Well this season helped me learn a lot about everyone. I know whose real and whose fake in here. Things will be different next year... at least on my end.

No one in this blog has the power to run over me LOL!
Member Since: October 28, 2006 Posts: 57 Comments: 30559
Quoting pottery:
LOL Hurristat. Changing the names of storms is one thing. Changing their gender is quite another. How can we be so insensitive? No wonder these things become hard to predict and all.


I have two friends, one named Rachel, and then one whose name is extremely similar to Rene, and they are complete opposites, and then to lump them together in the same storm... (shivers)
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WPB. Of course not.
Did you create it? No.

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Quoting Drakoen:


I know how to hold my ground and hold it well lol.
Surely have to in this blog, or u may just get run over. . . LOL

It was an interesting summer.

Interestingly enough, while many storms toasted our edges, and the SE part got fried, no storms actually ran right over us. Guess that means my 1926 / 1928 analog years were a bit off. . . .
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LOL Hurristat. Changing the names of storms is one thing. Changing their gender is quite another. How can we be so insensitive? No wonder these things become hard to predict and all.
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Pottery...and others...should I receive hate mail over this? Which I most likely will again....
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Ouch. (863) Gore doesn't seem to bother her. ;)
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Quoting CybrTeddy:
No, if a Storm maintains atleast TD status, with the LLC intact, the storm retains its name. If the LLC dissipates and then reforms then it gets a new name.


I was joking... I know that, but think how amusing it would be to have Alma-Arthur and Rene-Rachel in the same year. Alliterative names. Fun.
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It still looks like an open trough on the quicksat. No evidence of a well-defined surface circulation.
Member Since: October 28, 2006 Posts: 57 Comments: 30559
Come on...this is ironic...

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Amen, CybrTed (857). Ivan made a big loop over the southern US came back, redeveloped to a tropical storm again going into SW La. The NHC had a debate over keeping the same name, but that is how they did it.
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Quoting cycloone:
SO does 96L have a chance of becoming Rene??


Well, one thing we know. It's now moving north(1 MPH) and winds are at 35 miles per hour. All it needs to do is fully consolidate a center of circulation to be classified as a Tropical Depression. Tropical Disturbances(a.k.a. Invests) can approach TD and TS strength(remember Fay?). but rarely a hurricane(until forming that coc).
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Quoting pottery:
Hurristat, the Damsel in distress turned out to be some freak making the whole thing up.........


ooooohhh... :O
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859. JRRP

Link
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Quoting cycloone:
SO does 96L have a chance of becoming Rene??
The NHC gives it a 20-50%
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No, if a Storm maintains atleast TD status, with the LLC intact, the storm retains its name. If the LLC dissipates and then reforms then it gets a new name.
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Quoting BahaHurican:
Ah, the Dolly discussions!!! I remember that like yesterday. . . . lol Particularly how Drak was so quietly adamant, while most of the rest of us kept railing against him . . . LOL

Like kman, I really started to get the concept of convergence and divergence after that - Dolly was a good teacher. I think we had some better calls after that point from a lot of people.

Oh, and let's not forget all the people who kept writing off the NHC forecasts. . . . lol


I know how to hold my ground and hold it well lol.
Member Since: October 28, 2006 Posts: 57 Comments: 30559
yeppers...was called a liberal..(voted for Gov. Crist and Tom Rooney, bot Rep.)...i just found it ironic and funny when you pardon a turkey and do an interview in front of the machines that kill turkies..and yes...i am eating turkey for thanksgiving.
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Quoting sullivanweather:
The rule is if it retains tropical storm status it retains its name. If it drops down to a depression or remnant low that regenerates it gets a new name.


I thought it was as long as the kept issuing advisories. So if it drops down to td rene but they still issue advisories then it would stay rene. But if they issue the last advisory then then it gets the new name.
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Another sign around here says

"lawn cutting done here"

Think about the logistics involved there....
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I'm out - mucho work tomorrow
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SO does 96L have a chance of becoming Rene??
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This is in regard to the Atlantic-Pacific crossover storms.
Member Since: March 8, 2007 Posts: 273 Comments: 12612
The rule is if it retains tropical storm status it retains its name. If it drops down to a depression or remnant low that regenerates it gets a new name.
Member Since: March 8, 2007 Posts: 273 Comments: 12612
WPB, did you really get hate mail for that ?
Boggles the mind.
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844 Goef - No NO no LOL - let that one slide
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Quoting Tazmanian:
they no longer we name storm if a storm comes from the Atlantic if we get Rene here in the Atlantic and it move in to the E. Pacific it will still be called Rene


Last I checked they change the names.

Ex. 1996 Cesar (atlantic)- Douglas (pacific)
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Quoting Drakoen:


Don't give me a yard I might take a mile LOL!
Ah, the Dolly discussions!!! I remember that like yesterday. . . . lol Particularly how Drak was so quietly adamant, while most of the rest of us kept railing against him . . . LOL

Like kman, I really started to get the concept of convergence and divergence after that - Dolly was a good teacher. I think we had some better calls after that point from a lot of people.

Oh, and let's not forget all the people who kept writing off the NHC forecasts. . . . lol
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Quoting surfmom:
We did once have a night of "carnage"... and lost 6 hens -- it was early on. We didn't sink the fence and a racoon dug under and ... I had to pick up chicken parts -- then my kid and I didn't know what to do w/the bag... so we're driving around at night with , God, chicken parts in a hefty bag ....


Maybe I should post the Sarah Palin turkey pardon video again lol...I actually got hate mail for posting that.
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Hurristat, the Damsel in distress turned out to be some freak making the whole thing up.........
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they no longer we name storm if a storm comes from the Atlantic if we get Rene here in the Atlantic and it move in to the E. Pacific it will still be called Rene
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ROTFL Pottery !
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Quoting pottery:
Yes indeed. This season had some incredible moments.
The lonely damsel in distress with a hurricane approaching, trying to convince her stoned daddy to listen to reason.
Certain amazing revelations.
And storms that just would not follow instructions from the NHC or anyone.


I missed that. that is really depressing... (hides in corner)
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jfv was a classic...every storm in the atlantic was going to hit dade county...plus he brought the bow tie back into vogue
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....and talking about parts, there is a sign on the highway near here, advertising

"Used Japanese Body Parts"

I think it refers to Nissan and Toyota, doors and fenders and such, but I dare not stop to ask.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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