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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Hi everyone,

was hoping we are done with "swirls" but is that a "swirl" I see in the SW Caribbean?
Please tell me it is "nothing"..


bbl,
gams
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RAMSDIS floater is showing some good rotation in the extreme southwestern Caribbean just north of Panama. Has become better defined. NHC is sleeping...
Member Since: October 28, 2006 Posts: 57 Comments: 30832
Quoting hurristat:
Due to lack of... substance, what are your predictions for next year's storms, in the TS:Hurricane:Major Hurricane format. I'm thinking 15:8:5


I think:
Non-Named: 14
S/TS: 12
H:9
MH:6
Member Since: April 27, 2008 Posts: 29 Comments: 2097
Quoting stormwatcherCI:
NHC-seasons archive 1958-1994


Thanks for the help, but...
I have looked through that website 4-5 times now trying to find data for TDs. I can't though, because they stop supplying the data for TDs in 1990, because the TDs aren't in the ones that end -prelim/. Does anyone know another website with TD data for 1958-1990?? Thanks for the help
Member Since: October 15, 2008 Posts: 11 Comments: 2312
NHC-seasons archive 1958-1994
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Quoting Cotillion:
I'm going to say 14/7/3. Something tells me it won't be as bad.

I'll even go one step further!

Tropical Storms: Ana, Bill, Claudette, Fred, Ida, Joaquin, Mindy.

Hurricanes: Danny, Kate, Larry, Nicholas.

Majors: Erika, Grace, Henri.

I'm not going to predict on retirements though, as that's low.


I'll say Kate should me major, since every time its or a variation of its name has been used, it has been a Cat. 3
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Does anyone know where to find data on tropical depressions previous to 1991??
Member Since: October 15, 2008 Posts: 11 Comments: 2312
I'm going to say 14/7/3. Something tells me it won't be as bad.

I'll even go one step further!

Tropical Storms: Ana, Bill, Claudette, Fred, Ida, Joaquin, Mindy.

Hurricanes: Danny, Kate, Larry, Nicholas.

Majors: Erika, Grace, Henri.

I'm not going to predict on retirements though, as that's low.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting CybrTeddy:


Seems a little low, Its forcasted to be a La Nina.

17/9/5

is this all of our forecast for next year?
15/8/4
Member Since: March 29, 2008 Posts: 0 Comments: 2377
"Living with the Wolfman"
Wolfman 6
Wolves 0

Their time will come...
Member Since: September 11, 2008 Posts: 9 Comments: 10167
4:47 1st Qtr
(15) Michigan St (9-2, 6-1 Big Ten)
(8) Penn St (10-1, 6-1 Big Ten)
1 2 3 4
0
7
T
0
7

GameCast | Box Score | RealTime | Conversation


Daryll Clark pass complete to Derrick Williams for 9 yards to the PnSt 28 for a 1ST down.
Passing: Clark (PSU) 63 yds
Rushing: Royster (PSU) 15 yds
Receiving: Norwood (PSU) 49 yds
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thanx
Member Since: September 11, 2008 Posts: 9 Comments: 10167
Quoting stormwatcherCI:
After OSU's last touchdown, Michigan fumbled the kickoff return back to the Buckeyes. Todd Boeckman, in for Pryor, then found Brian Hartline for an 18-yard touchdown pass. The final is 42-7 Ohio State.



phale... darn it, no Michigan State team going to Rose Bowl. What was the score of the MSU-PSU game?
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Quoting KoritheMan:


>_>

Let's not talk about my philosophy regarding names, okay? LOL! :)


ok LOL
Member Since: October 15, 2008 Posts: 11 Comments: 2312
After OSU's last touchdown, Michigan fumbled the kickoff return back to the Buckeyes. Todd Boeckman, in for Pryor, then found Brian Hartline for an 18-yard touchdown pass. The final is 42-7 Ohio State.

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I missed it.
What was the score of the Mich Ohio St game ?
Member Since: September 11, 2008 Posts: 9 Comments: 10167
Quoting hurristat:


Just like in your philosophy for retiring names (LOL). We seem to get into that discussion A LOT!!!


>_>

Let's not talk about my philosophy regarding names, okay? LOL! :)
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Quoting KoritheMan:


La Nina may very well develop, but we don't know how strong just yet. I'm trying to remain conservative for the time being.


Just like in your philosophy for retiring names (LOL). We seem to get into that discussion A LOT!!!
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Quoting CybrTeddy:


Seems a little low, Its forcasted to be a La Nina.

17/9/5


Hey Korithe; Teddy
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Quoting CybrTeddy:


Seems a little low, Its forcasted to be a La Nina.

17/9/5


La Nina may very well develop, but we don't know how strong just yet. I'm trying to remain conservative for the time being.
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Quoting KoritheMan:
14/8/4


Seems a little low, Its forcasted to be a La Nina.

17/9/5
Member Since: July 8, 2005 Posts: 259 Comments: 24576
16/7/3
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14/8/4
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19:7:2
Due to lack of... substance, what are your predictions for next year's storms, in the TS:Hurricane:Major Hurricane format. I'm thinking 15:8:5
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Quoting twistermania:
Last time I saw snow was about 24 hours ago.


you need to get out some more!!! LOL
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Good afternoon! It's pretty cold in my town today; still below freezing!
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Been living here so long (36 yrs) now anything below 70 is freezing to me.
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Last time I saw snow was about 24 hours ago.
Quoting all4hurricanes:
Well it looks to late for anything else to form I think we half to wait till June 2009 in the meantime The southern cyclone will half to do
That sounds good to me. Had enough close calls this year. Dolly,Gustav,Ike and Paloma. Can't wait to take off the plywood for a few months.
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I sense a snowy surprise for Florida this winter!! It's forecast to be a cold and brutal winter for the eastern half.
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Wow, Hurristat! I part-time live in Holland (in the summer). South Haven (just north of me)got a foot. Benton Harbor (two miles south of me) was -8 F last night!
Well it looks to late for anything else to form I think we half to wait till June 2009 in the meantime The southern cyclone will half to do
Member Since: March 29, 2008 Posts: 0 Comments: 2377
Quoting stormwatcherCI:
They had snow in Miami, Fla in Jan 1977 but by then I had moved to Cayman. The last time I saw snow was in Pa. where I am originally from in 1964.

last time I saw snow was two minutes ago... LOL
Member Since: October 15, 2008 Posts: 11 Comments: 2312
They had snow in Miami, Fla in Jan 1977 but by then I had moved to Cayman. The last time I saw snow was in Pa. where I am originally from in 1964.
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Quoting twistermania:
I ahve about 3" on the ground right now, Surf.


I have about an inch... did you hear? Up in Holland, they got about 9!!! Also, you have the Lake Effect snow... i have the remnants of it, so I never get nearly as much as you do.
Member Since: October 15, 2008 Posts: 11 Comments: 2312
I ahve about 3" on the ground right now, Surf.
We had a beautiful dusting of snow in Cape Hatteras last night!! First time I've ever seen it stick on the ground here.
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Quoting twistermania:
I don't udnerstand C either, CI.


I've taught it to myself.
Member Since: October 15, 2008 Posts: 11 Comments: 2312
I don't udnerstand C either, CI.
ATTENTION!

Now, for my contest you can put eastern and central pacific hurricanes.
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Quoting hurristat:


Oh. I thought you lived in the Caymans. correct, and almost everywhere else in the world other than the United States uses Celsius, so I thought that would help you get a perspective.
I do live in Cayman but grew up in Miami. Temps here are reported in both F & C due to it being UK OT and close proximity to the US
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Quoting stormwatcherCI:
Sorry. Don't really understand celsius. Always think of temp in Farenheit.


Oh. I thought you lived in the Caymans. correct, and almost everywhere else in the world other than the United States uses Celsius, so I thought that would help you get a perspective.
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Quoting hurristat:


I meant Fahrenheit. Try -6 Celsius.
Sorry. Don't really understand celsius. Always think of temp in Farenheit.
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Afternoon all

As mentioned by Dr M, I am doing my Portlight Honor Walk on the Arthur Ravenel Jr bridge....



If you want you can watch me walk via the webcam. Join in the chat as well; it is always fun.

Hope everyone has a great Saturday!
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Quoting stormwatcherCI:
That's cool for us. Usually doesn't go below maybe 63-65 at night in the winter here. Very windy though so it feels cooler. Winds about 35 mph the past few days.


I meant Fahrenheit. Try -6 Celsius.
Member Since: October 15, 2008 Posts: 11 Comments: 2312
Quoting Jerrob:
Thanks. I know he wasnt a featured blogger anymore, but I dont see him on the list below either.


StormW's Blog is still there, but if you don't update or have any posts for a while, you drop off the bottom of the list...in which case you have to search alpabetically. Storm hasn't updated since the 10th.
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The SW caribbean disturbance wasn't mentioned in the TWO.
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Quoting hurristat:


only... LOL. It got down in the teens where I live.
That's cool for us. Usually doesn't go below maybe 63-65 at night in the winter here. Very windy though so it feels cooler. Winds about 35 mph the past few days.
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Thanks. I know he wasnt a featured blogger anymore, but I dont see him on the list below either.
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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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