Forecast for the winter of 2012 - 2013

By: Dr. Jeff Masters , 4:53 PM GMT on October 18, 2012

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Expect increased chances of a warmer than average winter across most of the western U.S., and a cooler than average winter across much of Florida, said NOAA in their annual Winter Outlook, released on October 18. The forecast also called for increased chances of a wetter than average winter along the Gulf Coast, and drier than average conditions in the Pacific Northwest and Upper Midwest. This year's forecast was more difficult than usual to make, said Mike Halpert, deputy director of NOAA’s Climate Prediction Center, due to the uncertainty about what El Niño may do. El Niño strongly impacts winter weather patterns, by altering the path of the jet stream and the associated winter storms that travel along the axis of the jet stream. We currently have neutral El Niño conditions over the tropical Pacific ocean, which means that ocean temperatures are near average along the Equator from the coast of South America to the Date Line. But from early July to mid-September, a borderline weak El Niño event appeared to be consolidating, and most of the El Niño computer models were calling for a full-fledged El Niño event to be in place by winter. That is now seriously in question, as we've had four straight weeks with neutral conditions. NOAA's Climate Prediction Center has dropped their odds of a winter El Niño event to 55%. El Niño events typically cause cooler and wetter winter conditions across the Southern U.S., and warmer than average conditions across much of the Northern U.S.



Figure 1. Forecast temperature (top) and precipitation (bottom) for the U.S. for the upcoming winter, as predicted in the NOAA Winter Outlook, released on October 18.

What will the Arctic Oscillation and North Atlantic Oscillation do?
While El Niño is usually a key factor controlling winter weather patterns, it is often overshadowed by the North Atlantic Oscillation (NAO)--a climate pattern in the North Atlantic Ocean of fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores High. The NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America and Europe more readily. This pattern is kind of like leaving the refrigerator door ajar--the Arctic refrigerator warms up, but all the cold air spills out into the house where people live. The NAO is a close cousin of the Arctic Oscillation (AO), and can be thought of as the North Atlantic component of the larger-scale Arctic Oscillation. Since the AO is a larger-scale pattern, scientists refer to the AO instead of the NAO when discussing large-scale winter circulation patterns. The winter of 2009 - 2010 had the most extremely negative NAO pattern (and AO pattern) since record keeping began in 1950. Vicious "Snowmageddon" winter storms occurred in both the U.K. and the United States that winter, as both Europe and North America suffered though an unusually cold and snowy winter (the NAO index was -1.67, beating the previous record of -1.47 set in the winter of 1962 - 1963.) Thus, the phase and strength of the AO/NAO pattern is a key factor controlling winter weather. Unfortunately, this pattern is not predictable more than about two weeks in advance, and thus was not considered by NOAA in their forecast for the upcoming winter.


Figure 2. The forecast for the winter of 2011 - 2012 released October 20, 2011 by NOAA called for a classic La Niña weather pattern over the U.S.--increased chances of warmer and drier weather over the Southern U.S., and cooler and wetter over the northern tier of states (top panels.) Nearly the entire nation ended up having a warmer than average winter, with the winter of 2011 - 2012 ranking as the 4th warmest winter on record. While the Southeast U.S. did see a very dry winter, as is typical in a La Niña year, Texas had an unusually wet winter. Part of the reason for the very mild winter was because the North Atlantic Oscillation (NAO), averaged over the winter, reached its most extreme positive value (+1.37) since record keeping began in 1950 (previous record: +1.36 during the winter of 1994 - 1995.)

Winter weather and the sunspot cycle
Another major influence on the AO and winter circulation patterns may be the 11-year solar cycle. Recent satellite measurements of ultraviolet light changes due to the 11-year sunspot cycle show that these variations are larger than was previously thought, and may have major impacts on winter circulation patterns. A climate model study published in Nature Geosciences by Ineson et al. (2011) concluded that during the minimum of the 11-year sunspot cycle, the sharp drop in UV light can drive a strongly negative AO pattern, resulting in "cold winters in northern Europe and the United States, and mild winters over southern Europe and Canada, with little direct change in globally averaged temperature." The winters of 2009 - 2010 and 2010 - 2011 both occurred during a minimum in the 11-year sunspot cycle and fit this pattern, with strongly negative AO conditions leading to cold and snowy winters in northern Europe and the Eastern U.S. There was more solar activity during the winter of 2011 - 2012, which may have contributed to the fact that AO conditions reversed, ending up positive. The coming winter of 2012 - 2013 will have even more solar activity than last winter (Figure 3), potentially increasing the odds of a warm, positive-AO winter in northern Europe and the United States.


Figure 3. The number of sunspots from 2000 - 2012 shows that solar minimum occurred during the winter of 2008 - 2009, and that solar activity is now approaching a peak, expected to arrive sometime in 2013. Image credit: NOAA Space Weather Prediction Center.

How will Arctic sea ice loss affect the winter?
Francis et al. (2009) found that during 1979 - 2006, years that had unusually low summertime Arctic sea ice had a 10 - 20% reduction in the temperature difference between the Equator and North Pole. This resulted in a weaker jet stream with slower winds that lasted a full six months, through fall and winter. The weaker jet caused a weaker Aleutian Low and Icelandic Low during the winter, resulting in a more negative Arctic Oscillation (AO), allowing cold air to spill out of the Arctic and into Europe and the Eastern U.S. Thus, summers with high Arctic sea ice loss may increase the odds of cold, snowy winters in Europe and the Eastern U.S. In my April 2, 2012 blog post, Arctic sea ice loss tied to unusual jet stream patterns, I discuss three additional research papers published in 2012 that argue for a major impact of Arctic sea ice loss on Northern Hemisphere weather in fall and winter, with sea ice loss causing an increase in the probability of negative-AO winters. But cold air may also be more likely to spill out of the Arctic in winter due to the decades-long pattern of warming and cooling of Atlantic Ocean waters known as the Atlantic Multidecadal Oscillation (AMO). A 2012 study by NASA scientists found that the warm phase of the AMO (like we have been in since 1995) causes more instances of atmospheric blocking, where the jet stream gets "stuck" in place, leading to long periods of extreme weather. It will be interesting to see how all these factors play out in the coming years. If these three newly-published studies are correct, the U.S. should see an increase in cold, snowy winters like 2010 - 2011 and 2009 - 2010 in coming decades, as Arctic sea ice continues to melt, affecting fall and winter atmospheric circulation patterns more strongly.

What happened during past winters with similar atmospheric conditions?
During a press conference today, Mike Halpert, deputy director of NOAA’s Climate Prediction Center, was asked to compare weather conditions this fall to those observed in previous years. The idea is that by looking at previous "analogue" years with similar progressions of the El Niño pattern, one might anticipate what the winter climate might be like. Halpert emphasized that this year is totally unique in the 63 years we've been keeping statistics on El Niño. Never before has an El Niño event begun to form in July and August, then quit in mid-September. Even if we did have a few analogue years, it wouldn't do any good, though--Halpert stated that we would need a data base of at least 1,000 years of historical data to make a skillful winter forecast based on analogue years.

Summary
I'm often asked by friends and neighbors what my forecast for the coming winter is, but I tell them to flip a coin, or catch some woolley bear caterpillars for me so I can count their stripes and make a woolley bear winter forecast (this year's Woolley Worm Festival in Banner Elk, North Carolina is this weekend, so we'll know then what the official Woolley Worm winter forecast is.) Making an accurate winter forecast is very difficult, as the interplay between El Niño, the AO/NAO, the AMO, Arctic sea ice loss, and the 11-year sunspot cycle is complex and poorly understood. I've learned to expect the unexpected and unprecedented from our weather over the past few winters; perhaps the most unexpected thing would be a very average winter during 2012 - 2013.

References
Francis, J. A., W. Chan, D. J. Leathers, J. R. Miller, and D. E. Veron, 2009: Winter northern hemisphere weather patterns remember summer Arctic sea-ice extent. Geophys. Res. Lett., 36, L07503, doi:10.1029/2009GL037274.

Honda, M., J. Inoue, and S. Yamane, 2009: Influence of low Arctic sea-ice minima on anomalously cold Eurasian winters. Geophys. Res. Lett., 36, L08707, doi:10.1029/2008GL037079.

Ineson, S., et al., 2011, Solar forcing of winter climate variability in the Northern Hemisphere, Nature Geoscience (2011) doi:10.1038/ngeo1282

Overland, J. E., and M. Wang, 2010: Large-scale atmospheric circulation changes associated with the recent loss of Arctic sea ice. Tellus, 62A, 1.9.

Petoukhov, V., and V. Semenov, 2010: A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents. J. Geophys. Res.-Atmos., ISSN 0148-0227.

Seager, R., Y. Kushnir, J. Nakamura, M. Ting, and N. Naik (2010), Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10, Geophys. Res. Lett., 37, L14703, doi:10.1029/2010GL043830.

Quiet in the Atlantic and Eastern Pacific
Forecasters at the National Hurricane Center get a rare break today, as there are no tropical cyclones or threat areas in either the Atlantic or Eastern Pacific to discuss. Most of the models are predicting that an area of disturbed weather capable of becoming a tropical depression will form in the Central Caribbean Sea south of Jamaica by the end of next week. Residents of Central America, Jamaica, Cuba, Haiti, and the Cayman Islands should anticipate the possibility of a multi-day period of very heavy rains affecting them late next week.

I'll have a new post on Saturday.

Jeff Masters

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NHC moved 99L from the origonal initialized position:

NHC 99L INVEST 20121020 1200 155N 0725W 295 051 1008 1010 0278 13 000 -999 -999 -999 -999 S -999 -999 -999 -999 -9 -99N -999W -999 -999 -999 -999



NHC 99L INVEST 20121020 1200 146N 0728W 280 051 1008 1010 0278 13 111 -999 -999 -999 -999 S -999 -999 -999 -999 -9 -99N -999W -999 -999 -999 -999
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Good morning/Evening all. Chilly here this morning. Any ideas on which way 99L will go? From what I'm seeing and reading, I'm not sure at all.
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Do we now have 90L???
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Member Since: August 6, 2011 Posts: 4 Comments: 37067
Africa still pumping out the waves..........
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Member Since: August 6, 2011 Posts: 4 Comments: 37067
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GFS at 153 hours,850 vort...........
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Quoting Grothar:


Oh, I'm looking. Anybody wake pottery up?
yeah he should be around now with this out there.
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Quoting LargoFl:
..GRO looks like we in florida should be watching this one carefully huh


Oh, I'm looking. Anybody wake pottery up?
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GFS at 120 hours,850 vort.................
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Quoting Grothar:
..GRO looks like we in florida should be watching this one carefully huh
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Quoting ces15hurricanes:
Invest 99L its much better organized. (Sandy)
yes sure is getting healty alright
Member Since: August 6, 2011 Posts: 4 Comments: 37067
Invest 99L its much better organized. (Sandy)
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Quoting MAweatherboy1:

I think "rocket fuel" would be a more accurate description, lol.


I didn't want the blog to get too exicted. :)
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Quoting kmanislander:
I have to head out now. Errands etc but will check in later.
Looking forward to your input.
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I have to head out now. Errands etc but will check in later.
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Quoting Grothar:


Is that "jet fuel"? :)

I think "rocket fuel" would be a more accurate description, lol.
Member Since: February 11, 2012 Posts: 82 Comments: 7638
Quoting Grothar:


Is that "jet fuel"? :)


Unfortunately yes. If the low closes off over that it could ramp up in short order.
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99L reminds me a lot of 98L in that it has plenty of convection but needs to consolidate it in order to be classified:



Btw 90L's floater is also up.
Member Since: February 11, 2012 Posts: 82 Comments: 7638
Quoting kmanislander:


Actually, it's the time of year I hate because these systems can do very unexpected things in the late season. They can also become very potent. Look at the area it will enter in the next 12 hours or so.



Is that "jet fuel"? :)
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Quoting Grothar:


I saw it first! :) I've been tracking the trough and it is really not very useful until we see how strong 99L gets and how fast it moves. Don't you hate these kind of systems?


Actually, it's the time of year I hate because these systems can do very unexpected things in the late season. They can also become very potent. Look at the area it will enter in the next 12 hours or so.

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Experimental higher resolution GFS ensembles, 168 hours:









Link
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Quoting kmanislander:


Both the Canadian and the Euro stall it out near 80W then swing it to the N over Jamaica.

Easy to see with steering like this. That big weakness may propagate to the East. Depends on the forecast steering which I have not looked at as yet.

As you said, it's all in the timing. Late season track forecasts can be a nightmare at times.



I saw it first! :) I've been tracking the trough and it is really not very useful until we see how strong 99L gets and how fast it moves. Don't you hate these kind of systems?
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Quoting stormwatcherCI:



LOL


Wont be long now lol
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Quoting Grothar:
The early models will show 99L moving WNW and moving over central Cuba. The later models will probably show a movement more towards the NW then back NE as the trough moves in. Timing will be interesting on this system.


Both the Canadian and the Euro stall it out near 80W then swing it to the N over Jamaica.

Easy to see with steering like this. That big weakness may propagate to the East. Depends on the forecast steering which I have not looked at as yet.

As you said, it's all in the timing. Late season track forecasts can be a nightmare at times.

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LOL
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SSD Floater is up for 99L.

Link
Member Since: April 29, 2009 Posts: 75 Comments: 14073
BAMM models take 99L generally on a WNW track for next 5 days, while more reliable GFS and Euro models consolidate the center of 99L southeast of Jamaica and move it on a general NNE or NE track beginning day 3.
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The early models will show 99L moving WNW and moving over central Cuba. The later models will probably show a movement more towards the NW then back NE as the trough moves in. Timing will be interesting on this system.
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Anticyclone overhead as well. Nothing to prevent 99L from developing, possibly quite quickly as the genesis of the system is not monsoonal but a Twave.

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Quoting MAweatherboy1:
Good morning. While this is highly unlikely to verify, check out the 0z CMC run... it brings future Sandy into the NE as an epic Nor'easter- 956mb in the second image at 204 hours!




that would be the bast thing that ever happened to me in a loooong time!
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Quoting stormwatcherCI:
I agree. This one definitely has it's eye on us. Some people may be jumping for joy right about now lol.


I know what you mean. Eventually a forecast pans out :-)
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SHIPS brings 99L up to a peak of 56kts in 60-72 hours, then weakens it from there as it indicates 30+ knots of shear beyond 4 days.
Member Since: February 11, 2012 Posts: 82 Comments: 7638
Quoting kmanislander:


Good morning
Interesting few days ahead
I agree. This one definitely has it's eye on us. Some people may be jumping for joy right about now lol.
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Quoting stormwatcherCI:
Thank you Nea. I wonder what the pressure is in this AOI.


Good morning
Interesting few days ahead
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WHXX01 KWBC 201239
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1239 UTC SAT OCT 20 2012

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL992012) 20121020 1200 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
121020 1200 121021 0000 121021 1200 121022 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 15.5N 72.5W 16.1N 74.4W 16.4N 76.4W 16.4N 78.3W
BAMD 15.5N 72.5W 15.8N 74.1W 16.1N 75.4W 16.2N 76.3W
BAMM 15.5N 72.5W 15.8N 74.2W 15.8N 75.7W 15.7N 77.1W
LBAR 15.5N 72.5W 16.6N 74.3W 17.6N 75.6W 18.5N 76.5W
SHIP 25KTS 32KTS 40KTS 47KTS
DSHP 25KTS 32KTS 40KTS 47KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
121022 1200 121023 1200 121024 1200 121025 1200

LAT LON LAT LON LAT LON LAT LON
BAMS 16.0N 80.6W 14.8N 85.0W 13.6N 88.6W 13.0N 91.3W
BAMD 16.3N 77.2W 16.6N 78.5W 17.5N 79.4W 19.8N 80.5W
BAMM 15.3N 78.4W 14.7N 80.5W 14.0N 81.7W 14.7N 80.9W
LBAR 19.2N 77.3W 19.9N 78.5W 21.2N 79.5W 22.6N 80.1W
SHIP 51KTS 56KTS 53KTS 48KTS
DSHP 51KTS 56KTS 53KTS 48KTS

...INITIAL CONDITIONS...
LATCUR = 15.5N LONCUR = 72.5W DIRCUR = 295DEG SPDCUR = 10KT
LATM12 = 14.7N LONM12 = 70.5W DIRM12 = 295DEG SPDM12 = 10KT
LATM24 = 14.0N LONM24 = 69.0W
WNDCUR = 25KT RMAXWD = 0NM WNDM12 = 20KT
CENPRS = 1008MB OUTPRS = 1010MB OUTRAD = 150NM SDEPTH = S
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

Member Since: April 29, 2009 Posts: 75 Comments: 14073
A minute after I say the other AOI could get an invest it does and we now have invest 90L.

Also if the 06Z GFS verified at 180-204hrs I would get 3-6 inches of snow. that is unlikely at this time though but it is getting closer to winter.
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Hey, look, a two'fer: 90L (the easternmost AOI)--

BEGIN
NHC_ATCF
invest_al902012.invest
FSTDA
R
U
040
010
0000
201210201236
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 90, 2012, DB, O, 2012102012, 9999999999, , , , , , METWATCH, , AL902012
AL, 90, 2012102012, , BEST, 0, 199N, 493W, 25, 0, DB, 0, , 0, 0, 0, 0,
Member Since: November 8, 2009 Posts: 4 Comments: 13471
Good morning everyone, I see we have invest 99L and it is up to 30%. The other AOI is also looking good this morning and it too could be invested in. Right now it is a wet cool fall morning with a good amount of leaves on the ground.
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As I was saying:

BEGIN
NHC_ATCF
invest_al992012.invest
FSTDA
R
U
040
010
0000
201210201236
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 99, 2012, DB, O, 2012102012, 9999999999, , , , , , METWATCH, , AL992012
AL, 99, 2012101912, , BEST, 0, 140N, 690W, 20, 1009, DB, 0, , 0, 0, 0, 0,
AL, 99, 2012101918, , BEST, 0, 143N, 697W, 20, 1009, DB, 0, , 0, 0, 0, 0,
AL, 99, 2012102000, , BEST, 0, 147N, 705W, 20, 1009, DB, 0, , 0, 0, 0, 0,
AL, 99, 2012102006, , BEST, 0, 151N, 715W, 20, 1009, DB, 0, , 0, 0, 0, 0,
AL, 99, 2012102012, , BEST, 0, 155N, 725W, 25, 1008, DB, 34, NEQ, 0, 0, 0, 0, 1010, 150, 0, 0, 0, L, 0, , 0, 0, INVEST, S,
Member Since: November 8, 2009 Posts: 4 Comments: 13471
Quoting stormwatcherCI:
Thank you Nea. I wonder what the pressure is in this AOI.
The initial ATCF file is usually updated to the full file (with barometric pressure, windspeed, and location history) within a short period; I expect it any time...
Member Since: November 8, 2009 Posts: 4 Comments: 13471
Member Since: July 12, 2007 Posts: 0 Comments: 5998

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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.