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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Query, if someone could answer this via WU mail I would appreciate it?

Has anyone been to the Dominican on Vacation.. and if so, where and what did they think? I am looking at going on a last minute vacation down there.. or somewhere warm.

How bad was the Dominican area hurt by the Hurricanes this year?I know they were hit by few of the TD's.
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Anyone watch Twister? Pretty cool movie, it was just on TNT.
Member Since: July 8, 2005 Posts: 259 Comments: 24574
I can't wait till tomorrow we could have unforeseen Rene in a week
very late storms are so great
Good night
Member Since: March 29, 2008 Posts: 0 Comments: 2377
534. beell
You're humor is a little on the dry side.

And dusty too! I'll work on it some.
LOL
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quick everyone think of a clever thing to say when Rene forms before it is too late!
Member Since: March 29, 2008 Posts: 0 Comments: 2377
Quoting beell:


Aw, c'mon. Wish. Based on the over-abundant preponderance of querulous FL-based posts regarding recent anamolous sensible weather,...

You be da only one!


I lived somewhere where it snowed I probably would wish for snow. I post about Florida because I live in Florida lol. You're bombastic writing doesn't make it any harder to understand what you are saying lol.

You're humor is a little on the dry side.
Member Since: October 28, 2006 Posts: 57 Comments: 30825
Quoting 15hurricanes:
2008 Atlantic hurricane season:

Nov. 01-10: Paloma!
Nov. 11-20: ---

Rene will be next or not ??
Nov. 21-30: ?
Dec. 01-10: ?
Dec. 11-20: ?
Dec. 21-31: ?


Quoting GeoffreyWPB:
no..no...no...no..and no...jmho...done for the season


LOL ya I don't wanna eat another crow
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no..no...no...no..and no...jmho...done for the season
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Maybe it was a.....COOKBOOK!!!...(have to be a Twilight Zone fan to get it)...
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Quoting GeoffreyWPB:
maybe the aliens were delivering candy cane flavored egg nog!


That's thinking like the NHC at this time of the year

LOL

(don't bash me guys I'm clearly J/K)
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maybe the aliens were delivering candy cane flavored egg nog!
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ah man they fixed it to yellow now

its yellow on Post 510 too

too bad I liked the new green color

well at least I saved a picture of it :)
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Quoting GeoffreyWPB:
maybe they will make it red and white..candy cane colored!


mmmmmmmmmm candycane

LOL

PS it came from OuTeR SpAcE!!!!
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pretty cool video..

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maybe they will make it red and white..candy cane colored!
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wow
I looks for an online Ouija board and all they did was connect me to dead people it told me nothing about other storms of 2008 lol
Member Since: March 29, 2008 Posts: 0 Comments: 2377
520. JRRP
Quoting all4hurricanes:

green?!?
whats that mean go?
but the important part is that NHC recognized it
Maybe its less than a 0% chance

green means 99% i think
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Ummm...Ahhhhhhh...


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well since its that time of year I suppose when they "fix" it, the circle will be red and green

LOL!
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Quoting GeoffreyWPB:
think they are drinking their egg nog a little to soon!


mmmmmmmm eggnog
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Quoting all4hurricanes:

green?!?
whats that mean go?
but the important part is that NHC recognized it
Maybe its less than a 0% chance


Quoting all4hurricanes:
I realized green is the opposite of red and the scale is yellow to red so green is the low end of the scale in another dimension


LOL
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All I cared about was MSU and MU. Both lost! Good for me! LOL
Halftime:
Okla 42
Texas Tech 7
Member Since: September 11, 2008 Posts: 9 Comments: 10165
I realized green is the opposite of red and the scale is yellow to red so green is the low end of the scale in another dimension
Member Since: March 29, 2008 Posts: 0 Comments: 2377
think they are drinking their egg nog a little to soon!
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wpb actually its about 30,000 a month to heat the building iam a high rise superintendent 10 floors 140 apartments boiler heat 6 gas fire burners heat the building 2 gas fire burners make the domestic hot water temp set on building heat at 120f supply return comes back at about 85f with about 24 psi pressure that keeps the inside temps at about 75 76 all winter inside
Member Since: July 15, 2006 Posts: 178 Comments: 56021

green?!?
whats that mean go?
but the important part is that NHC recognized it
Maybe its less than a 0% chance
Member Since: March 29, 2008 Posts: 0 Comments: 2377
Quoting Cotillion:
By the way guys, on the SST map, anyone else noticed the Northern Australian anomaly?

It goes from around 30C waters to about 14...


I saw that too, but I think they're over 32-33 C instead and are really high.b
Member Since: October 15, 2008 Posts: 11 Comments: 2312
high of 40 for me in Berrien Srings, MI on Thanksgiving. HOW HOT! lol
I couldn't even imagine that Keeper..are your heating bills outrageous up there?
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your 10-day forcast 15 brings you down to 54 Thanksgiving morning with a high of 72
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as of 930pm 17.2f chill 9f already down 2 degrees passed the forecasted low for tonight they say 19 but its already 17.2
Member Since: July 15, 2006 Posts: 178 Comments: 56021
YouTube "Live" Tonight ...Link

YouTube LIVE! November 22nd at 8PM
Eric
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Part concert, part variety show and part party, the event will bring to life many of the amazing videos and talent that YouTube viewers have already made popular.

A global event that will feature a live broadcast from San Francisco and Tokyo.


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wpb i may not see 67 again for quite sometime
Member Since: July 15, 2006 Posts: 178 Comments: 56021
Good evening...
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not cold at all...below average though..right now about 67 in west palm beach..
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stl i think we will be in winters cold gripe till at least near end of dec and it will be snowy as well looks like a storm every few days with the first starting on monday and one following behind every few days after that first half of dec may be quite stormy
Member Since: July 15, 2006 Posts: 178 Comments: 56021
how cold is it in south florida, WPB?
I love the cool weather down here in so. fla. As long as we do not get any hard freezes that damage the crops and our economy...I am all for it!
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Love the cold! What is it future, 40 degrees in Florida? That's warm.
I honestly cannot stand the cold; this week has been in really tough in Florida.
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Cool weather has me wanting to hibernate --adios
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Quoting KEEPEROFTHEGATE:
18 f out side my door wind chill 9 f
I would just shrivel up and die...no doubt of it
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iam in southern ontario near western lake ontario
Member Since: July 15, 2006 Posts: 178 Comments: 56021

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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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