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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938. sporteguy03
10:50 PM GMT on November 24, 2008
Yep its an Ike!
Member Since: July 7, 2005 Posts: 0 Comments: 5417
937. CaicosRetiredSailor
2:28 PM GMT on November 24, 2008
NEW BLOG
Member Since: July 12, 2007 Posts: 0 Comments: 6069
936. TampaSpin
2:23 PM GMT on November 24, 2008
I just updated my blog....and played some Rock for my Rock friends including me.....:)

TampaSpins Weather Blog Link
Member Since: September 2, 2007 Posts: 179 Comments: 20448
935. HIEXPRESS
2:20 PM GMT on November 24, 2008
The CLP5 (climo) model can't be wrong every time, or else it wouldn't be climo would it? hmmm?
Member Since: October 13, 2005 Posts: 4 Comments: 2156
934. RTLSNK
1:40 PM GMT on November 24, 2008
930 - MissNadia - Let me explain it this way, I keep a large broom by the back door going into my garage so I can grab it as I go down the two steps into the garage if I see a large wolf spider, if its close to one of the three doors I hit the auto button and sweep it out into the driveway, if it jumps or runs toward me, then it gets whacked!!
Member Since: September 3, 2008 Posts: 0 Comments: 22130
932. GeoffreyWPB
1:31 PM GMT on November 24, 2008
SFWMD still doesn't have any models up on 96...Gonna try to do the dreaded X-Mas shopping today.
Member Since: September 10, 2007 Posts: 0 Comments: 11540
930. MissNadia
1:23 PM GMT on November 24, 2008
Quoting RTLSNK:
928 - TampaSpin - looks like something I had in my garage yesterday!!

Did you kill it ???
Member Since: July 27, 2008 Posts: 0 Comments: 3003
929. RTLSNK
1:10 PM GMT on November 24, 2008
928 - TampaSpin - looks like something I had in my garage yesterday!!
Member Since: September 3, 2008 Posts: 0 Comments: 22130
928. TampaSpin
1:01 PM GMT on November 24, 2008
Member Since: September 2, 2007 Posts: 179 Comments: 20448
927. TampaSpin
12:49 PM GMT on November 24, 2008
Good morning everyone.....
Member Since: September 2, 2007 Posts: 179 Comments: 20448
926. RTLSNK
12:42 PM GMT on November 24, 2008
Morning everyone - 41*F in Macon this morning, rain on the way coming out of the NW, already south of Atlanta.
Member Since: September 3, 2008 Posts: 0 Comments: 22130
925. MissNadia
12:36 PM GMT on November 24, 2008
God Morning from Coastal N.C.
30 F..clear skies..calm winds and a forecast high of 61... nice fall day!
Member Since: July 27, 2008 Posts: 0 Comments: 3003
924. Cotillion
12:34 PM GMT on November 24, 2008
Quoting JRRP:
Link


Seems Costa Rica has bought the Tampa-Jacksonville Bubble... Weird runs. GFDL scares me more, with the intensity... and there's only been two other R's used. Roxanne and Rita, both of which were retired.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
923. JRRP
11:59 AM GMT on November 24, 2008
Link
Member Since: August 16, 2007 Posts: 0 Comments: 6213
921. JRRP
11:53 AM GMT on November 24, 2008
000
ABNT20 KNHC 241145
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
700 AM EST MON NOV 24 2008

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS OVER THE SOUTHWESTERN CARIBBEAN SEA AND
ADJACENT LAND AREAS ARE ASSOCIATED WITH A BROAD AREA OF LOW
PRESSURE. THERE HAS BEEN LITTLE CHANGE IN ORGANIZATION DURING THE
PAST SEVERAL HOURS BUT THERE IS STILL A POTENTIAL FOR A TROPICAL
DEPRESSION TO FORM DURING THE NEXT DAY OR TWO IF THE SYSTEM REMAINS
OVER WATER. REGARDLESS OF WHETHER OR NOT A TROPICAL CYCLONE
FORMS...HEAVY RAINFALL AND LOCALIZED FLOODING WILL BE POSSIBLE OVER
PORTIONS OF PANAMA...COSTA RICA...AND NICARAGUA DURING THE NEXT
COUPLE OF DAYS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
Member Since: August 16, 2007 Posts: 0 Comments: 6213
920. surfmom
11:39 AM GMT on November 24, 2008
Morning, Checking to see what 96L has done through the night --
Member Since: July 18, 2007 Posts: 30 Comments: 26536
919. Cotillion
11:38 AM GMT on November 24, 2008
Quoting JRRP:
GFDL
Link


Bizarre run.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
918. JRRP
11:34 AM GMT on November 24, 2008
GFDL
Link
Member Since: August 16, 2007 Posts: 0 Comments: 6213
917. all4hurricanes
11:19 AM GMT on November 24, 2008
don't we know it
well gotto go
Member Since: March 29, 2008 Posts: 0 Comments: 2377
915. all4hurricanes
11:12 AM GMT on November 24, 2008
Trends continue
i think we're getting a TS soon
Member Since: March 29, 2008 Posts: 0 Comments: 2377
913. BahaHurican
11:09 AM GMT on November 24, 2008
Gotta go. . . work :o(. . .

Have a great day, all!
Member Since: October 25, 2005 Posts: 19 Comments: 22728
912. BahaHurican
11:08 AM GMT on November 24, 2008
Didn't someone suggest yesterday that once this Twave got into the WCar things could get interesting?


...TROPICAL WAVES...
TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 74W S OF 17N
MOVING W 10-15 KT. SATELLITE IMAGERY INDICATES CYCLONIC
CIRCULATION COINCIDING WITH THIS WAVE. A MAXIMUM IN DEEP LAYER
MOISTURE COINCIDES WITH THIS WAVE BASED ON TOTAL PRECIPITABLE
WATER PRODUCT FROM CIMSS. ALSO...UPPER AIR TIME-HEIGHT ANALYSIS
FOR CURACAO...LOCATED IN THE NETHERLANDS ANTILLES NEAR
12N69W...RECENTLY DEPICTS VEERING OF THE MEAN LOW/MID-LEVEL FLOW
FROM NE TO SE...SUGGESTING THAT THIS WAVE HAS LIKELY MOVED W OF
CURACAO. SCATTERED MODERATE CONVECTION IS OCCURRING WITHIN
150 NM EITHER SIDE OF THE WAVE AXIS S OF 16N. THIS WAVE IS
BECOMING ABSORBED BY THE BROAD LOW LEVEL CYCLONIC CIRCULATION
ASSOCIATED WITH THE 1007 MB SURFACE LOW NEAR 10N80W...WHICH IS
DISCUSSED IN THE SPECIAL FEATURE SECTION ABOVE.
Member Since: October 25, 2005 Posts: 19 Comments: 22728
911. BahaHurican
11:06 AM GMT on November 24, 2008
BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...SPECIAL FEATURE...
IN THE SW CARIBBEAN...A 1007 MB SURFACE LOW IS CENTERED N OF
PANAMA NEAR 10N80W. LOW LEVEL CONVERGENCE IN THE VICINITY OF
THIS SURFACE LOW IS INTERACTING WITH DEEP LAYER MOISTURE OVER
THE W CARIBBEAN TO RESULT IN NUMEROUS SHOWERS AND THUNDERSTORMS
OVER THE CARIBBEAN S OF 15N W OF 77W...INCLUDING PORTIONS OF
COSTA RICA...PANAMA...AND E NICARAGUA. THIS SHOWER AND
THUNDERSTORM ACTIVITY HAS INCREASED AND BECOME BETTER ORGANIZED
OVER THE LAST DAY...AND SOME ADDITIONAL DEVELOPMENT OF THIS
SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT DRIFTS
SLOWLY WESTWARD. REGARDLESS OF WHETHER OR NOT A TROPICAL CYCLONE
FORMS...HEAVY RAINFALL AND LOCALIZED FLOODING WILL BE POSSIBLE
OVER PORTIONS OF PANAMA...COSTA RICA...AND NICARAGUA DURING THE
NEXT COUPLE OF DAYS.
Member Since: October 25, 2005 Posts: 19 Comments: 22728
909. hurricanemaniac123
10:57 AM GMT on November 24, 2008
It looks like 96L is getting a spin. If quikscat finds a well-defined surface circulation today, we will have TD 18.
Member Since: September 21, 2008 Posts: 9 Comments: 688
908. KoritheMan
9:37 AM GMT on November 24, 2008
The QuikSCAT data for 96L is out, and there is no closed surface circulation as of yet -- not that I expected there to be, just saying. There is a bit of a wind shift, though.
Member Since: March 7, 2007 Posts: 602 Comments: 21302
907. KoritheMan
9:25 AM GMT on November 24, 2008
I may be wrong, but from the data I've looked at, and also per satellite imagery, I think whatever center there is (be it low or mid-level, what have you) is in the middle of the convective mass, southeast of that heavily sheared northern area of convection. Cyclonic turning seems evident there to me.
Member Since: March 7, 2007 Posts: 602 Comments: 21302
906. Cotillion
7:50 AM GMT on November 24, 2008
Still getting heavily sheared, you can tell easily by the way convection is on its north side.

However, the shear is slowly relaxing.. was under 50 kts a couple of days ago. Now about 30, and the tendency is a lowering from 5-20kts in that area. So, it may even be favourable soon. As the current tracking doesn't suggest it'll move north, it won't encounter some of the stronger shear sitting over the Greater Antilles.

I definitely thought the season was done, guess I could be wrong... I'll order mine in advance with Subway BBQ sauce please. ;)
Member Since: August 23, 2008 Posts: 7 Comments: 5300
905. HadesGodWyvern (Mod)
7:35 AM GMT on November 24, 2008
India Meteorological Department
Tropical Cyclone Outlook
11:30 AM IST November 24 2008
=========================================

A low pressure area has formed over Sri Lanka and adjoining neighborhood. It is likely to concentrate into a depression during the next 48 hours.

Elsewhere in the north Indian Ocean
-------------------
Convective clouds are seen over south Andaman Sea, south Bay of Bengal,a nd southeast Arabian Sea.
Member Since: May 24, 2006 Posts: 52 Comments: 46909
904. HadesGodWyvern (Mod)
6:57 AM GMT on November 24, 2008
A broad low pressure (96L) located just north of Panama is producing large area of showers and thunderstorms over the southwestern Caribbean Sea and adjoining land areas. Showers and thundserstorm activity has continued to become better organized.. and a tropical deprssion could form in the next day or two if the system remains over waters as it drifts slowly westward.

Regardless of whether or not a tropical cyclone forms.. heavy rainfall and localized flooding will be possible over portions of Panama, Costa Rica, and Nicaragua during the next couple of days.
Member Since: May 24, 2006 Posts: 52 Comments: 46909
903. LostTomorrows
5:19 AM GMT on November 24, 2008
Hahaha I love that Palin video. She's totally oblivious, and it is so ironic.

Anyway, that 96L looks really good right now. I'm guessing Rene might actually be forming soon.
Member Since: August 26, 2008 Posts: 0 Comments: 617
902. Skyepony (Mod)
5:11 AM GMT on November 24, 2008

Member Since: August 10, 2005 Posts: 225 Comments: 39376
901. nishinigami
5:00 AM GMT on November 24, 2008
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.


This was my first hurricane season living in LA. With that said, the aforementioned season nearly cost me all of my hair. Luckily I found this website and though the storms didn't want to follow the rules, listening in here made me feel a lot better and helped me make the decision on when to evacuate from Gustav. Thanks bunches from a newbie!
Member Since: August 24, 2008 Posts: 2 Comments: 221
900. HurricaneKing
4:02 AM GMT on November 24, 2008
Quoting CosmicEvents:
My question was just one last chance this season to spoof the numerous posts we see every year when a storm's out there, 1000 miles from land.
.
Now watch...it's somehow gonna' happen...lol


If it does it better bring snow. If it doesn't I'm going to hunt you down for jinxing me. LOL
Member Since: July 6, 2005 Posts: 71 Comments: 2485
899. HIEXPRESS
3:44 AM GMT on November 24, 2008
I got my first avocados on my tree this year. I understand this is pretty far north to go long enough without a freeze to get production. A freeze of significant duration kills the tree back to about 6', but it grows back fast.
Member Since: October 13, 2005 Posts: 4 Comments: 2156
897. weatherblog
3:22 AM GMT on November 24, 2008
Quoting CosmicEvents:
My question was just one last chance this season to spoof the numerous posts we see every year when a storm's out there, 1000 miles from land.
.
Now watch...it's somehow gonna' happen...lol


lol Okay I'm glad that wasn't a serious question.
Member Since: July 10, 2006 Posts: 27 Comments: 1623
896. CosmicEvents
3:20 AM GMT on November 24, 2008
My question was just one last chance this season to spoof the numerous posts we see every year when a storm's out there, 1000 miles from land.
.
Now watch...it's somehow gonna' happen...lol
Member Since: August 3, 2005 Posts: 10 Comments: 5684
895. BahaHurican
3:14 AM GMT on November 24, 2008
Amazing to see that map on 24th November. Practically Turkey Day!
Member Since: October 25, 2005 Posts: 19 Comments: 22728
894. BahaHurican
3:14 AM GMT on November 24, 2008
Quoting pottery:
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.
Read something earlier this week saying the news crew asked her if she wanted to move and she said "No worries". I think sometimes she forgets she's not playing to only a "hometown" audience who wouldn't find the turkey slaughter particularly out of the ordinary. And face it, people, 100 years ago, most people prepped their own birds, so they wouldn't have been shocked by the vid.
Member Since: October 25, 2005 Posts: 19 Comments: 22728
893. JRRP
3:13 AM GMT on November 24, 2008
Link
why here don´t show 96L ?
Member Since: August 16, 2007 Posts: 0 Comments: 6213
892. pottery
3:11 AM GMT on November 24, 2008
WPB, I agree. I understand the irony too.

Member Since: October 24, 2005 Posts: 0 Comments: 24881
891. BahaHurican
3:09 AM GMT on November 24, 2008
Isn't OBX Outer Banks, NC???

[scratching head]
Member Since: October 25, 2005 Posts: 19 Comments: 22728
890. Drakoen
3:09 AM GMT on November 24, 2008
Member Since: October 28, 2006 Posts: 57 Comments: 30825
889. GeoffreyWPB
3:05 AM GMT on November 24, 2008
it's called ironic...that's all...
Member Since: September 10, 2007 Posts: 0 Comments: 11540
888. hurristat
3:03 AM GMT on November 24, 2008
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
Member Since: October 15, 2008 Posts: 11 Comments: 2312

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