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

Share this Blog
3
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 88 - 38

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19Blog Index

Oh, and below is an interesting one that has not been answered to date that I am aware of. Please, if anyone has information to the contrary, do not hesitate to post. I'll read it. I listen to both sides and then make an intelligent decision. I think it's obvious the way I am leaning at the moment, but I don't believe we know enough yet. Read, read, read. JMO.

In particular, would love for this to be answered from the linked:

"If you believe there is evidence of the CO2 driver theory in the available data please present a graph of it."

Link

And here's the graph using same MSU sat data from the letter:



Again, open, but would really like an answer to this one in particular.
Member Since: Posts: Comments:
Weather Channel lays off staff
By KRISTI E. SWARTZ

The Atlanta Journal-Constitution

Wednesday, November 19, 2008

The Weather Channel, which NBC Universal bought in September, has laid off some of its staff. It is unclear how many people were cut or whether they are receiving a severance package.

NBC Universal and Weather Channel officials would not comment beyond a statement.

“The economic realities of recent months have created challenges for everyone in our business. In addition, when NBC Universal purchased the Weather Channel earlier this year, we expected that there would be cost synergies as part of company reorganization. While it is always difficult to lose valued employees, we are doing our best to minimize the impact, and remain committed to providing the highest quality content that our viewers have come to expect from the Weather Channel.”




Member Since: Posts: Comments:
windchill up here has dropped to 20 and expecting single digit windchills tonight,
Member Since: Posts: Comments:
Bone,

It should be fair on Monday before the storm moves in with a southwesterly flow. That should sufficiently warm the boundary layer into the 40s for the coastal plain and mid to upper 30's across the interior. The airmass will be rather dry as the storm moves in through so temperatures will likely wet bulb down once the precip starts and with the strong dynamics associated with the storm itself and the impressive height falls with the mid-level low coming overhead it should quickly change to snow across any rainy interior locations. Along the coastal plain the changeover won't likely occur until the secondary low forms and pulls north of the latitude of the location in question.
Member Since: Posts: Comments:
Quoting atmoaggie:


??? No, just not convinced that the climate models have been given good physics and good initial conditions to work with. And then not convinced that they have good data to be validated against.

If you must call me names, call me an unconvincedist. And maybe call those that are in denial that there are possible weaknesses to our current capabilities to reliably measure and/or model climate parameters a denialist.


Well, you can add me to the denialist club. This global warming garbage has become a religion to some. It's all garbage in/garbage out. So far hundreds of NOAA's climate stations in the U.S. have been found out of compliance regarding placement, which 99% of the time provides higher than normal temperature readings. Couple that fact with the alarming discovery that NOAA is also "correcting" past temperature history by lowering historical temperatures and all of the data is completely inaccurate. Their climate models cannot even predict past weather accurately when they know the outcome, so how can they predict future weather? It's all part of the environmental wacko movement that desires everyone to be riding bicycles and eating nothing but uncooked vegetables.
Member Since: Posts: Comments:
Re: 72:

The AJC article didn't name names.

Is there a list somewhere of who was let go?

I used to work with Sharon Resultan and hope she wasn't one of the mets who lost their job.

Thanks.
Member Since: Posts: Comments:
yep,holding my breath as far as my job is concerned,not good times in the country
Member Since: Posts: Comments:
61. grayingwindsurfer

Here's a peer review on model validation:

PDF

Edited to add link to the multitude contributing to that one:

Link
Member Since: Posts: Comments:
Quoting hurricane23:


Yep some of those included Dave Schwartz,Dennis Smith and a few more. Article HERE.


Dave Schwartz was a weirdo anyways. Sorry to hear about the rest. A lot of people getting laid off because of the economy.
Member Since: October 28, 2006 Posts: 57 Comments: 29935
People have been complaining about the weather being too cold in Florida.
But in my area its picture perfect.

Fort Myers, Fort Myers, Florida (PWS)
Updated: 5 sec ago
75.4 F / 24.1 C
Clear
Humidity: 52%
Dew Point: 56 F / 14 C
Wind: 3.0 mph / 4 km/hfrom the NW
Pressure: 30.14 in / 1020.5 hPa (Steady)
Heat Index: 78 F / 25 C

Member Since: Posts: Comments:
No problem NE, I gave them pottery's address.
Member Since: Posts: Comments:
Rob,have a great weekend
shephard,a little short of feed this week,can you take care of my birds for me,much appreciated
Member Since: Posts: Comments:
Yeah, Bone, probably not smart but if I'm gonna get old, I'll go kickin and screamin all the way...

Gotta finish up some stuff, almost forgot it's Friday. If you get a chance, drop by my blog and look at the new pic. I'll be checking in later tonight.

Have a great weekend!
Member Since: Posts: Comments:
Forecast Earth is history.
Member Since: Posts: Comments:
Hey NEwxguy
Send some feed down here for these Sand Hill Cranes you sent me.
Member Since: Posts: Comments:
Heard about that, Adrian.

And does anyone have an further news on SJ from his burger challenge? :p
Member Since: Posts: Comments:
Quoting NEwxguy:
h23,on air people got laid off?


Yep some of those included Dave Schwartz,Dennis Smith and a few more. Article HERE.
Member Since: Posts: Comments:
LOL Rob. I know the feeling, happens to me once in a blue moon. Usually its my wife asking me what dumbass thing I did LOL
Member Since: Posts: Comments:
h23,on air people got laid off?
Member Since: Posts: Comments:
High school buddy, have to get together and act like teenagers once in a while. Usually his wife will call me up the next morning wanting to know what I did to her husband cause he hurts too much to get up. Great fun.
Member Since: Posts: Comments:
Wow how sad to see the weather channel personalities i grew up watching just get booted.Its a tough situation that continues unfolding good luck to those that got laid off.

In all honesty the way the current economy is this comes as no suprise.
Member Since: Posts: Comments:
LOL sounds like fun :) Used to do that with jet skis not boats though.
Member Since: Posts: Comments:
Quoting Bonedog:
Hey Rob hows chil errr Sunny Florida?


Beautiful day, T-shirt weather. Supposed to go play in the jet-boats this weekend...Still wondering about that as the last time we ended up in "jet boat wars" (ie: trim the nozzle up and try to soak each other) I got soaked and the engine died. Not really warm enough for that so I'll take foul weather gear.
Member Since: Posts: Comments:
Hey Rob hows chil errr Sunny Florida?
Member Since: Posts: Comments:
50 Bonedog

LOL and he sings too!

Hey Bone
Member Since: Posts: Comments:
62. NEwxguy

DOH! Didn't think of that. Thats where the boundry layer comes in. Nice catch NE =) Time to go relook at the models and try to figure this out now.
Member Since: Posts: Comments:
well,the saving grace Bone,is the ocean is still relatively warm,so except for inland areas,a strong storm will bring in warmer atlantic air.
Member Since: Posts: Comments:
Quoting Atmoaggie:
Ummm, you do still have initial conditions and naturally, error, in those initial forcings and current states, assumed periods of the climate cycles, and number of other parameters that will grossly effect the output.

Not to mention that the results, primarily in relative terms, can only be validated against those same poor initial conditions that went into the seasonal forecast.

This isn't even worth discussing, really, until a climate model actually scores a decent skill, and not against a surface observation from a station on a pole over a BBQ pit or from within the plume of jet exhaust next to a runway.


Sorry, but you are wrong. If you put different initial conditions into the same seasonal model, you will get very different forecasts. If you put different initial conditions into a long-term climate model, you will get very similar forecasts, proving that putting in accurate initial conditions are not important.

What is important it that crude (by today's standards) climate models in the 1980s predicted, among other things, greater warming in the arctic than at mid-latitudes. This has proven to be correct. The skill of 1980s models is not bad and the quality and complexity of the models are increasing.

Dismissing good, scientific, peer-reviewed results with suggestions that some people are collecting data over BBQ pits or in jet exhaust is insulting to the hard-working people collecting data and indicates a lack of thought. I prefer political rants be posted on political blogs
Member Since: Posts: Comments:
sulli thanks for that post. I didnt hink about the boundry layer only due to the fact how long the cold air has been in place up here. I figured the thermo profile was below freezing all the way up.

As far as the model diffrences I am going with a blend right now. I know the euro does better in the medium range as far as track and the canadian usually has a grasp of the temps in the time frame, but from my personal observations only, the GFS does good with picking up Miller B systems as far as coastal cyclogenisis goes.

Not saying the I95 is going to get socked but could be the first accumualting snowfall in the cities. Again depending on thermo profile.
Member Since: Posts: Comments:
Dr. Masters,
Thank you for yet another extremely clearly written, informative post. As a ground-water-flow modeler, I understand the initial- vs. boundary-condition issues well and am intrigued.

Member Since: Posts: Comments:
Looks to be a stormy December,like last year.
Member Since: Posts: Comments:
There were 5 of those storms on yesterday's GFS run...

This biggest concern for me with the upcoming storm for Monday-Wednesday will be initial boundary layer temps as the precip moves on Monday afternoon/evening. Right now it looks like anyone under 1,000' is likely to remain rain until the strong dynamics pull through.

Second is where does the secondary surface low form. Right now the GFS has gone furthest south with the low while the Canadian and Euro have trended slightly north. That would keep the precip confined to New England and northern New York with all points south and west receiving the first weakening band of precip from the parent low. I think this storm will be a big one for the mountains of northern New York and New England. There might be some 2' totals at sugarloaf, Stowe, Killington and the other northern ski resorts but for the Catskill region south and west the snow accumulations will likely be confined to the higher terrain and much lighter, generally under 4".

Member Since: Posts: Comments:
yea NE the latest GFS which I posted in 51 shows the Low east of you and keeps you on the cold side as well.

Sun 12/07

this is for tuesdays system, your on the warm side of it
Tues 11/25
Member Since: Posts: Comments:
Quoting MichaelSTL:


Wow. What a denialist...


??? No, just not convinced that the climate models have been given good physics and good initial conditions to work with. And then not convinced that they have good data to be validated against.

If you must call me names, call me an unconvincedist. And maybe call those that are in denial that there are possible weaknesses to our current capabilities to reliably measure and/or model climate parameters a denialist.
Member Since: Posts: Comments:
bone,the forecasts i've seen so far are expecting the low to come up right over me.Have you seen models moving more out to the east?
Member Since: Posts: Comments:
round 2



NE this ones for you =)
Member Since: Posts: Comments:


let it snow
let it snow
let it snow
Member Since: Posts: Comments:
A seasonal or a short-term weather forecast is what mathematicians call an "initial value" problem....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.

Ummm, you do still have initial conditions and naturally, error, in those initial forcings and current states, assumed periods of the climate cycles, and number of other parameters that will grossly effect the output.

Not to mention that the results, primarily in relative terms, can only be validated against those same poor initial conditions that went into the seasonal forecast.

This isn't even worth discussing, really, until a climate model actually scores a decent skill, and not against a surface observation from a station on a pole over a BBQ pit or from within the plume of jet exhaust next to a runway.
Member Since: Posts: Comments:

Freeze Warning Link


Statement as of 12:04 PM CST on November 21, 2008

... Freeze warning in effect from midnight tonight to 8 am CST
Saturday...

The National Weather Service in New Orleans has issued a freeze
warning... which is in effect from midnight tonight to 8 am CST
Saturday. The freeze watch is no longer in effect.

A light freeze is possible late tonight and early Saturday
morning across portions of east central Louisiana including the
Baton Rouge Metro area. A cold dome of high pressure will settle
over the mid and lower Mississippi Valley with clear skies and
light winds expected. Low temperatures may range from 29 to 32
degrees with freezing temperatures possibly lasting for 2 to 6
hours.

Stay tuned to NOAA Weather Radio... commercial radio or
television stations... or your cable television provider for the
latest on this possible freeze situation in and around the Baton
Rouge Metro area.

A freeze warning means sub-freezing temperatures are imminent or
highly likely. These conditions will kill crops and other
sensitive vegetation. Care should be taken for outdoor pets.
Member Since: Posts: Comments:
Loving it =)

Models are starting to look better and better for a storm next week
Member Since: Posts: Comments:
Hey,Bone,enjoying this cold I bet?
Member Since: Posts: Comments:
afternoon folks.

Nice topic, so as others have said Ill stick to my wolly worms and squirl tails =) LOL
Member Since: Posts: Comments:
quick "comment" for today



Oh how they fell

Link
Member Since: Posts: Comments:
Quoting KoritheMan:
Winter has struck with a vengeance here in southeast Louisiana. I don't remember it getting this cold this early in quite a number of years.

It's currently 48F here, and the overnight low could reach the upper 20s.


I second that. I do not remember having to scrape a frozen car in mid November like I did on Tuesday. 29 in Slidell that morning and likely that or a little less tonight, too.

EDIT: Nevermind, I am full of it. I went looking at the records and see an instance of ~30 at least once almost every year. I also see highs pushing 80 in every November, too. Link
Member Since: Posts: Comments:
Okay, how does Orca say it?

Complete blog refresh!
(sorry no mirror site)

not really a "complete refresh" but a more up to date photo since you liked the last one.
Feel free to post your comments on my page.
Thanks!
Member Since: Posts: Comments:
Winter has struck with a vengeance here in southeast Louisiana. I don't remember it getting this cold this early in quite a number of years.

It's currently 48F here, and the overnight low could reach the upper 20s.
Member Since: Posts: Comments:
Yo northern bloggers....Missing some birds???
The Sand Hills don't seem to care much for Orca's "clipper" he sent your way.
Member Since: Posts: Comments:
Dr.Masters thank you for a balanced update.
Member Since: Posts: Comments:

Viewing: 88 - 38

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.