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Jet stream moved northwards 270 miles in 22 years; climate change to blame?

By: Dr. Jeff Masters , 4:11 PM GMT on June 05, 2008

Climate change is forcing the jet stream higher and closer to the pole in both the Northern and Southern Hemisphere, according research published this April in the journal Geophysical Research Letters. In their paper, "Historical trends in the jet streams", researchers Cristina Archer and Ken Caldeira of Stanford's Carnegie Institution of Washington analyzed data from 1979-2001, and found that the Northern Hemisphere jet stream moved northward at approximately 125 miles per decade (270 miles during the 22-year period of the study). The jet moved higher by 5-23 meters during this period, and the wind speeds decreased by about 1 mph. Archer and Caldeira's study confirms other research showing a poleward movement of the jet stream in recent decades (Fu et al., 2006; Hu and Fu, 2007). All of these changes are consistent with the behavior of the jet stream predicted by global warming theory. For example, Lorenz and DeWeaver (2007) found poleward shifts of the jet stream by 2100 in the forecasts of 15 climate models used to formulate the "official" word on climate, the 2007 Intergovernmental Panel for Climate Change (IPCC) report. However, the authors were careful not to say how much of this shift in the jet stream was due to natural causes versus human-caused climate change. It is unknown if the jet stream has natural decades-long changes in its path that could account for the observed poleward shift.

Figure 1. The jet stream is located where the strongest winds at the top of the troposphere are found (35,000-45,000 feet high, 200-300 mb in pressure).

Archer and Caldeira note that "These changes in jet stream latitude, altitude, and strength have likely affected, and perhaps will continue to affect, the formation and evolution of storms in the mid-latitudes and of hurricanes in the sub-tropical regions." They don't specify what these changes might be. There is very little research that has been done suggesting how changes in the jet stream might affect hurricane formation and strength. One effect we may begin to see in coming decades is a reduction and/or delay in the number of hurricanes that recurve northward out to sea. Recurvature occurs when a hurricane begins to "feel" the westerly winds of the jet stream. As the jet stream continues to move northward and weaken as the globe warms, we can expect that hurricanes moving though the Caribbean will be less likely to recurve, resulting in more hurricane strikes in Mexico and Central America. Unfortunately, the quality of the Atlantic hurricane database for non-U.S. landfalls is not very good, and it will be several decades before we will be able to tell if the number of hurricane landfalls in Mexico and Central America is increasing due to a poleward shift in the jet stream.

Fu, Q., C. M. Johanson, J. M. Wallace, and T. Reichler (2006), Enhanced mid-latitude tropospheric warming in satellite measurements, Science, 312, 1179, doi:10.1126/science.1125566.

Hu, Y., and Q. Fu (2007), Observed poleward expansion of the Hadley circulation since 1979, Atmos. Chem. Phys. Disc., 7, 9367.9384.

Lorenz, D. J., and E. T. DeWeaver (2007), Tropopause height and zonal wind response to global warming in the IPCC scenario integrations, J. Geophys. Res., 112, D10119, doi:10.1029/2006JD008087.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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1264. cchsweatherman
4:59 PM EDT on June 08, 2008
Looks like there may be some consolidating convection with a thunderstorm over Grand Bahama Island. Thus far the most solid convection I have seen with this ULL after breaking apart from the TUTT. Broward County may get some decent rainfall if this can hold.
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1263. nash28
9:01 PM GMT on June 08, 2008
I told my wife that it is pretty sad when you watch it rain as if it is an event:-)
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1262. nash28
9:00 PM GMT on June 08, 2008
Seabreeze JP. Nothing frontal in nature. Just the SB and boundary.
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1259. nash28
8:57 PM GMT on June 08, 2008
I'm trying StormW! Friday night I was spittin nails as the seabreeze was pinned to the coast. I watched the storms move just to the S of me and pummel Parrish, Skyway Bridge, etc..
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1255. nash28
8:54 PM GMT on June 08, 2008
OMG! I finally got rain here in Apollo Beach! It hadn't rained at all in two months! 10 minutes only, but the lawn got a sip. My wife and I went in the driveway and just let it soak us!
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1254. Patrap
3:54 PM CDT on June 08, 2008
There goes the ol GPA..JFV
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4:20 PM EDT on June 08, 2008
Howdy Surfmom - any thunder with that rain? Looks like more showers coming.

TVS X 3 in MI
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1248. surfmom
8:09 PM GMT on June 08, 2008
post1233 - that would make my day!!!!It will make alot of peoples day! We're so dry out east - it's like the hay could go combustible - I am assuming PM rain???? Today's brief shower in SRQ/SWFL was a delight. Cools everything off. A sigh of relief from humans, plants and critters.
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4:05 PM EDT on June 08, 2008
1242. cchsweatherman
Over the past few hours, there has been a marked increase in shower and thunderstorm activity over the Bahamas with the ULL.

Are there any thunderstorms there? There doesn't seem to be a lot around today. Tracker Must not be much ice up there.

Bahamas Radar
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1246. Greyelf
3:01 PM CDT on June 08, 2008
Dear God, I wish I was able to give some of the rain we've been getting here in Nebraska to those that want it. We've had enough. The Missouri River (that I live only about half a mile from) has risen about 5' in 3 days. In addition, overnight, we got about another 1 3/4" of rain locally WITH an added bonus of a surprise tornado that decided we all needed to get up at 2:30 a.m. I SO hate night tornadoes.
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8:07 PM GMT on June 08, 2008
Antsy wishing ...
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1244. weatherfromFlorida
8:02 PM GMT on June 08, 2008
Why are we looking at an ULL?
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1243. Drakoen
7:45 PM GMT on June 08, 2008
Moisture looks to be streaming in with the onshore easterly flow and the moisture from that upper level low. Looks like a line for Palm Beach and Broward county.
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1242. cchsweatherman
3:20 PM EDT on June 08, 2008

Over the past few hours, there has been a marked increase in shower and thunderstorm activity over the Bahamas with the ULL.
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7:36 PM GMT on June 08, 2008
No, just moisture/upper disturbances interacting with land/daytime heat. It will fall flat soon enough.
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1240. Buhdog
7:32 PM GMT on June 08, 2008
This ULL looks like it's getting stronger
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1239. Buhdog
7:30 PM GMT on June 08, 2008
How muck of that rainfall is making it to the surface with that ULL? I know the seabreeze clollisions will be plentifull...but how bout the stuff associated with the ULL?
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1238. Patrap
2:18 PM CDT on June 08, 2008
GOES-12 IR Loop GOM Link

Uptown, New Orleans, Louisiana (PWS)
Updated: 22 sec ago
Mostly Cloudy

94.1 F / 34.5 C

Mostly Cloudy
Humidity: 24%
Dew Point: 52 F / 11 C
Wind: Calm
Wind Gust: 0.0 mph / 0.0 km/h
Pressure: 30.12 in / 1019.9 hPa (Falling)
Heat Index: 91 F / 33 C
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1237. moonlightcowboy
2:16 PM CDT on June 08, 2008
...hey, fellas! Good work! Maybe some of those smarts will rub off in here - I could use some of them! ;)
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1235. Weather456
3:11 PM AST on June 08, 2008
1223. cchsweatherman 2:50 PM AST on June 08, 2008

Thanks...When its ur passion it comes very easy.
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1234. Patrap
2:11 PM CDT on June 08, 2008
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1233. cchsweatherman
3:02 PM EDT on June 08, 2008
Based upon my latest analysis, it appears that South Florida may see an extended period with good rain chances as the ULL may stall over Western Florida or just off the SW Florida Gulf Coast sometime tomorrow night. The computer models keep South Florida under higher than normal (between 50 and 60%) rain chances until Wednesday at the earliest. With the upper-level and lower-level ridges breaking down over the Southeast and moving into the Central Atlantic, it will create a much more southerly tropical flow throughout the Southeast US. So, the bottomline is this; the dry spell will come to an end this week in the Southeast United States as the dictatorial high pressure ridge will finally collapse.
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1232. cchsweatherman
3:01 PM EDT on June 08, 2008
Right now, I stand at a 3.29 GPA after my first year at BCC. If it weren't for my CHM1041 class, it could be higher.
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1230. cchsweatherman
2:56 PM EDT on June 08, 2008
1226. JFV 2:55 PM EDT on June 08, 2008
yes I am sir, what was your final grade in ENC1101? Are you due to graduate from BCC anytime soon?

My final grade in ENC1101 was an A. Easy course in my opinion. As per your second question, don't know yet. It all depends upon how many courses I schedule myself with this year. Like I have stated before, I decided to take the summer off and earn some money working. By the way, starting July 1st, BCC will become Broward College as it will become the first community college to transform into a four-year college.
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1228. msphar
6:54 PM GMT on June 08, 2008
1097. Got them, thanks Pearl!
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1227. cchsweatherman
2:51 PM EDT on June 08, 2008
Right now, I'm not expecting any tropical systems to form until late June at the earliest as we have incredible subsidence occuring throughout the Atlantic Basin. Even with well-above average SSTs in the Caribbean, Gulf, and off Western Africa, if you don't have any upward motion in the atmosphere, you won't have thunderstorms, which means you won't have any tropical systems.

To respond to your request JFV, its nearly impossible to create a representation as to the steering currents in the Atlantic and projected storm tracks as the steering currents have continued to fluctuate throughout the basin. Once I see more consistency in the steering currents, then I can more accurately create a graphic displaying various scenarios.
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1224. cchsweatherman
2:50 PM EDT on June 08, 2008
1221. JFV 2:43 PM EDT on June 08, 2008
Hey Weatherman, you dealt with ENC1102 already my friend?

Just took ENC1102 this past semester and received a B in the class. Tough class since it entails writing and responding to various forms of literature; something that I've never done a great job on. Are you taking the course right now?
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1223. cchsweatherman
2:46 PM EDT on June 08, 2008
Thanks for the update 456. You did a terrific job explaining something that, at times, can get quite complicated. I saved it in my Favorites so that I may refer back to it anytime I need assistance tracking tropical waves. You continue to impress me with your vast wealth of knowledge regarding the tropics. I look forward to working together in tracking tropical systems this season with you and to further learn about tropical weather from someone who has quickly gained my utmost respect. Keep up the great work.
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1222. Drakoen
6:42 PM GMT on June 08, 2008
Not much going on in the Atlantic basin with MJO subsidence over the CATL and deep layered ridging over the eastern sea board. One thing to note is the ensemble forecast for a negative NAO prevailing mid-late June. We should see a weaker A/B high and finally get our monsoon trough to come up with the slackening in the tradewinds getting our SST's up. Latest SSTs from NOAA TCHP page are showing that 26 degree Celsius isotherm slowly reaching up to 15N in the EATL and in the CATL east of 45W.
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1218. Drakoen
6:36 PM GMT on June 08, 2008
Thank God! Its looks like that line will hit my area.
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1217. cchsweatherman
2:26 PM EDT on June 08, 2008
Just stopping in really quick here and will be mostly lurking through the afternoon. Just watching satellite loops on the ULL in the Central Bahamas, it seems like some convection has begun building around the ULL (much more than at any point today).

Right now, there is a solid streamer developing over Grand Bahama Island with some steady rainfall that looks poised to move into southern Palm Beach and Broward County over the next few hours. I will be watching this radar throughout the day for additional showers and even storms to pop.
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1216. hydrus
6:18 PM GMT on June 08, 2008
SURFMOM-just saying hello,glad to see you are getting a little rain.We are about 20 inches behind where we should be in my neck of the woods.
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1215. hydrus
6:13 PM GMT on June 08, 2008
WEATHER 456-Very good post on tropical waves.
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1214. moonlightcowboy
1:11 PM CDT on June 08, 2008

Still slightly cooler water in the scATL.
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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