Our extreme weather: Arctic changes to blame?

By: Dr. Jeff Masters , 9:50 PM GMT on December 16, 2011

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"The question is not whether sea ice loss is affecting the large-scale atmospheric circulation...it's how can it not?" That was the take-home message from Dr. Jennifer Francis of Rutgers University, in her talk "Does Arctic Amplification Fuel Extreme Weather in Mid-Latitudes?", presented at last week's American Geophysical Union meeting in San Francisco. Dr. Francis presented new research in review for publication, which shows that Arctic sea ice loss may significantly affect the upper-level atmospheric circulation, slowing its winds and increasing its tendency to make contorted high-amplitude loops. High-amplitude loops in the upper level wind pattern (and associated jet stream) increases the probability of persistent weather patterns in the Northern Hemisphere, potentially leading to extreme weather due to longer-duration cold spells, snow events, heat waves, flooding events, and drought conditions.


Figure 1. Arctic sea ice in September 2007 reached its lowest extent on record, approximately 40% lower than when satellite records began in 1979. Sea ice loss in 2011 was virtually tied with the ice loss in 2007, despite weather conditions that were not as unusual in the Arctic. Image credit: University of Illinois Cryosphere Today.

Summertime Arctic sea ice loss: 40% since 1980
The Arctic has seen a stunning amount of sea ice loss in recent years, due to melting and unfavorable winds that have pushed large amounts of ice out of the region. Forty percent of the sea ice was missing in September 2007, compared to September of 1980. This is an area equivalent to about 44% of the contiguous U.S., or 71% of the non-Russian portion of Europe. Such a large area of open water is bound to cause significant impacts on weather patterns, due to the huge amount of heat and moisture that escapes from the exposed ocean into the atmosphere over a multi-month period following the summer melt.


Figure 2. The extent of Arctic sea ice loss in the summer July - August - September period in 2007 was about 1.4 million square miles (3.6 million square kilometers) greater than in 1980, according to the University of Illinois Cryosphere Today. For comparison, the lost ice coverage (orange colors) was equal to an area about 44% of the size of the contiguous U.S., or 71% of the non-Russian portion of Europe.

Arctic sea ice loss can slow down jet stream winds
Dr. Francis looked at surface and upper level data from 1948 - 2010, and discovered that the extra heat in the Arctic in fall and winter over the past decade had caused the Arctic atmosphere between the surface and 500 mb (about 18,000 feet or 5,600 meters) to expand. As a result, the difference in temperature between the Arctic (60 - 80°N) and the mid-latitudes (30 - 50°N) fell significantly. It is this difference in temperature that drives the powerful jet stream winds that control much of our weather. The speed of fall and winter west-to-east upper-level winds at 500 mb circling the North Pole decreased by 20% over the past decade, compared to the period 1948 - 2000, in response to the extra warmth in the Arctic. This slow-down of the upper-level winds circling the pole has been linked to a Hot Arctic-Cold Continents pattern that brought cold, snowy winters to the Eastern U.S. and Western Europe during 2009 - 2010 and 2010 - 2011.


Figure 3. West-to-east jet stream wind speeds at 500 mb (approximately 18,000 feet or 5,600 meters) in the mid-latitudes (40 - 60°N) over North America between 1948 and 2010. During fall (October - November - December) and winter (January - February - March), jet stream winds weakened by about 20%, from 13 - 14 m/s to 10.5 - 11 m/s. Spring (AMJ) and summer (JAS) winds changed little during this time period.

Arctic sea ice loss may increase the amplitude of jet stream troughs and ridges
The jet stream generally blows from west to east over the northern mid-latitudes, with an average position over the central U.S. in winter and southern Canada in summer. The jet stream marks the boundary between cold polar air to the north and warm subtropical air to the south, and is the path along which rain and snow-bearing low pressure systems ride. Instead of blowing straight west-to-east, the jet stream often contorts itself into a wave-like pattern. Where the jet stream bulges northwards into a ridge of high pressure, warm air flows far to the north. Where the jet loops to the south into a trough of low pressure, cold air spills southwards. The more extreme these loops to the north and south are--the amplitude of the jet stream--the slower the waves move eastward, and consequently, the more persistent the weather conditions tend to be. A high-amplitude jet stream pattern (more than 1000 miles or 1610 km in distance between the bottom of a trough and the peak of a ridge) is likely to bring abnormally high temperatures to the region under its ridge, and very cold temperatures and heavy precipitation underneath its trough. The mathematics governing atmospheric motions requires that higher-amplitude flow patterns move more slowly. Thus, any change to the atmosphere that increases the amplitude of the wave pattern will make it move more slowly, increasing the length of time extreme weather conditions persist. Dr. Francis discovered that during the early 1960s, a natural pattern in the atmosphere called the Arctic Oscillation increased the amplitude of the winter jet stream pattern over North America and the North Atlantic by more than 100 miles, increasing the potential for long-lasting weather conditions. The amplitude of the winter jet fell over 100 miles (161 km) during the late 1960s, remained roughly constant during the 1970s - 1990s, then increased by over 100 miles again during the 2000s. This latest increase in wave amplitude did not appear to be connected to the Arctic Oscillation, but did appear to be connected to the heating up of the Arctic due to sea ice loss. A warmer Arctic allows ridges of high pressure to build farther to the north. Since temperatures farther to the south near the bases of the troughs are not changing much by comparison, the result is that the amplitude of the jet stream grows as the ridges of high pressure push farther to the north. Thus it is possible that Arctic sea ice loss and the associated increases in jet stream amplitude could be partially responsible for some of the recent unusual extreme weather patterns observed in the Northern Hemisphere. This is preliminary research that has yet to be published, and much more work needs to be done before we can confidently link Arctic sea ice loss with an increase in extreme weather, though.


Figure 4. A high-amplitude jet stream pattern observed over the U.S. on December 13, 2011. Instead of blowing straight west-to-east, the jet was contorted into a southward-bulging trough of low pressure that brought cold temperatures and a snow storm to Southern California, and a northwards-bulging ridge of high pressure that brought record warm temperatures to portions of the eastern 2/3 of the country. The axis of the jet stream is marked by the strongest winds (green and light blue colors) at the top of the lower atmosphere (200 - 300 mb pressure level.)

Earlier snow cover melt on Arctic land also increases the amplitude of jet stream troughs and ridges
As Earth's climate has warmed over the past 30 years, the Northern Hemisphere has seen a dramatic drop in the amount of snow cover in spring (April, May, and June.) Spring is coming earlier by an average of three days per decade, and the earlier arrival of spring has significantly reduced the amount of snow on the ground in May. Less snow on the ground means the land surface can heat up more readily, and May temperatures in Arctic have increased significantly over the past 30 years. Dr. Francis found that the upper-level wave amplitude has increased by over 100 miles (161 km) in summer over the past decade, and this change appears to be connected to the decline in May snow cover. Thus, reduced May snow cover due to global warming may be causing higher-amplitude jet stream patterns, potentially leading to slower-moving weather patterns that favor extreme weather in summer, such as heat waves, drought, and flooding. Note that significant changes to the upper-level atmospheric circulation in spring were not observed, so springtime extreme weather events like the 2011 flooding and tornadoes in the U.S. cannot be connected to changes in the Arctic sea ice or high-latitude snow cover using this research.

Related posts
Florida shivers; Hot Arctic-Cold Continents pattern is back
Jet stream moved northwards 270 miles in 22 years; climate change to blame?

Jeff Masters

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What a killer storm....Very sad those photos...

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Quoting sar2401:


Very sad, Aussie. Every time I hear only three or four people were killed in a storm in southeast Asia, I know it will always grow into the hundreds or thousands. :(


It gets worse.

At least 180 dead after storm pummels Philippines

At least 180 people are dead after Tropical Storm Washi pummeled the Philippines, officials said Saturday.

The deaths occurred in areas such as Iligan and Cagayan de Oro cities and Compostela Valley and Zamboanga del Norte provinces, said Benito Ramos, chairman of the National Disaster Risk Reduction and Management Council.

At least 400 people are missing after the storm, which is called Sendong locally. More than 2,000 have been rescued, according to the Armed Forces of the Philippines.

Defense Secretary Voltaire Gazmin said officials are investigating reports that an entire village was swept away.

Flash flooding overnight -- following 10 hours of rain -- fueled the devastation, compounded by overflowing rivers and tributaries. As much as 20 centimeters (8 inches) of rain fell within 24 hours in some areas.

Ramos said despite government warning, some did not evacuate.

Though Washi was headed away from the Philippines on Saturday, trouble could loom for Vietnam, as the storm's westerly path could cross Ho Chi Minh City on Tuesday.

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Quoting AussieStorm:
Photo's from Cagayan de Oro, Iligan City, Philippines







Very sad, Aussie. Every time I hear only three or four people were killed in a storm in southeast Asia, I know it will always grow into the hundreds or thousands. :(
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I find it slightly amusing to see all the back and forth about if a hurricane should have been a 4 or 5. We don't have 4.5 hurricanea, compared to say, a 7.1 earthquake. We know the release of energy much more precisely from earthquakes than we do for hurricanes, but even two earthquakes of the same magnitude won't produce the same amount of damage due to epicentral depth, local landforms, and a whole host of variables. We have had category 3 (maybe it was a 3.9) hurricanes that produced mcuh more damage than some category 4's. Who really cares if it was a 4 or 5? The damage and loss of life is what's important, and that won't change by recategorizing a storm. Seems like a lot of wasted energy for not much return. Of course, I'm willing to enlightened on why this issue is so vital to some of you.
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Photo's from Cagayan de Oro, Iligan City, Philippines





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Quoting Inyo:
RWT:

what? if vast areas of ice turn to open water, it does NOT take a long time for changes to take effect. They are immediate - instead of being -50 degrees or whatever, the open water moderates temperatures to near freezing. That's a tremendous change.

And about ice now growing substantially, yes, it happens every year, it's called winter. But, if you compare to other years at this time of year, no, ice isn't increasing. Where do you get this stuff from?


Without getting into the issue of melting Artic ice, your understanding of sea ice and the sea water beneath it is deficient. I've done scuba diving through three feet of ice in Baffin Bay. Bad idea if you're claustrophobic. :) The air temperature was about 42F. Sea water, because of it's increased salinity over freshwater, doesn't begin to freeze until it reaches about 28F. The water under the ice is rarely below 27F, and the lowest I saw was 25F. The ice acts as an insulator, keeping the water at just below the freezing point, but not allowing it to turn to ice because of the pressure of the ice cap above it. The thickness of the ice increases during the long Artic nights and melts during the long Artic summers. However, it takes a lot of sun to melt three or four feet of ice, and many places have ice more than 30 feet deep. There are many thinner spots along the edges of the ice pack and due to local topography. I would think the main issue with more open water is that it will take much longer for the absorbed heat to turn back to ice during the winter. If the ice isn't at least a couple of feet thick by summer, it will melt again. This heats the exposed sea water, and thins the ice at the edges of the open water. Over the long run, enough open water will make it impossible to regain the lost sea ice unless we have unusually cold summers for an extended period of time.
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Quoting Skyepony:
Atleast 3 died from Washi hitting the Philippines.

Corsica, France has a wind whipped, raging wild fire going.


Sendong/Washi toll hits 143



The death toll from tropical storm Sendong (international codename: Washi) rose to 143 on Saturday with more than 100 others missing after widespread flash floods in Mindanao, officials said.

The military said 95 bodies were recovered in Cagayan de Oro, a major port on Mindanao island, while the National Disaster Risk Reduction and Management Council said 48 people were killed elsewhere on the island.

A total of 125 other people were missing in Cagayan de Oro, said regional military spokesman Colonel Leopoldo Galon.

As of early Saturday, rescuers had recovered the bodies of 69 victims in Cagayan de Oro City, in nearby Iligan City and the Zamboanga del Norte areas of Dapitan and Polanco.

In Cagayan de Oro City alone, 51 were confirmed dead when floodwaters reached more than one meter deep early Saturday.

Twenty of the victims – many of them children – were recovered in Barangay (village) Tambo alone, one of the villages that dotted the swelling Cagayan de Oro River.

The Philippine Daily Inquirer was there when the bodies were being retrieved.

Emil Raña, city local government operations officer, said 22 villages came underwater when Sendong dumped rains. The floods were worsened by high tide, he said.

Armin Cuenca, head of the Oro Alert, said people were warned early on but many refused to leave their homes.

Cuenca said this worsened the situation when floodwaters started rising.

Bryan Cabillo of Tambo said his wife and three children were carried by the rushing floodwaters that swept their home late Friday.

He said his efforts to save them were futile as he too struggled against the strong current.

In nearby Iligan City, 15 people — including broadcaster Enie Alzonado of Radyo Mo Nationwide — died in the floods.

Mayor Lawrence Cruz said the bodies of the victims had been recovered.

Chief Superintendent Celso Regencia, Iligan City police chief, said they got reports that 40 people were killed in the floods but these were being verified.

Cruz said he was basing his data from actual recovery figure but admitted the death toll could increase as more than 200 others were reported missing as of midday Saturday.

The floods were worst, Cruz said because even areas that did not have floods in the past were deluged.

He said in many areas, the water was more than one meter deep.

“In the flood-prone districts, houses were either underwater or washed away.

Many families had to be rescued from the roof of their houses,” Cruz said.

The floodwaters have since subsided and this could speed up the search and rescue efforts, he said.

In Zamboanga del Norte, Governor Rolando Yebes said three persons died in the flood waters that hit villages in Dapitan and Polanco.

“Iyong tubig umabot lampas tao,” he said by phone.

Yebes said the floods were also worsened by high tide.

“Disaster personnel continue to monitor and assess the situation to determine actual number of families affected,” he said.

Lieutenant Colonel Randolph Cabangbang, spokesman of the Western Mindanao Command based in Zamboanga City, said soldiers were deployed to help in the search and rescue operation in flooded areas of Mindanao.

Cabangbang said early Saturday that in ILigan City alone, many residents were still on the roof of their houses.

He said the residents – many of them children – were chilling from fear and being wet – when plucked out.

The total number of people displaced by the floods was still being documented.

But in Cagayan de Oro, which still has no electricity as of Saturday morning, some 20,000 people were being assisted in at least 10 evacuation centers, according to Social Welfare Secretary Dinky Soliman.

In Iligan City, Cruz said “thousands had been displaced” but the actual number was still being determined.

The Iligan Bloggers Society had started a fund drive for the flood victims.

The group said they preferred canned goods and packed foods and clothing but donors could also send cash.

Details of the fund drive can be found on the group’s blog page.

Sendong capsizes cargo ship off Dumaguete; all aboard rescued



A cargo vessel anchored of off Dumaguete ran aground and capsized after it was battered by big waves spawned by Tropical Storm Sendong about 4 a.m. Saturday., the Philippine Coast Guard said.

Three women, a two-year-old boy and 28 crew members were rescued by the Philippine Coast Guard and other groups that responded to the distress signal sent by MV Ever Transport III.

The women were wives of crew members who had boarded the vessel to spend time with their husbands, the Coast Guard said. One of them brought their son.

Lieutenant Commander Agapito Bibat, commander of the Dumaguete Coast Guard station, said the vessel dropped anchor off the Dumaguete port Friday night and was battered by big waves around midnight.

One of the rescued crewmembers, who was not immediately identified, said they had asked permission to dock at the Dumaguete port but were denied, so they remained anchored off the coast.

Waves battered the boat and swept it to the shore in Barangay (village) Calindagan, about one kilometer away, where it ran aground and capsized around 4 a.m.

The rescued passengers and crewmembers of the ill-fated cargo vessel were taken to the Calindagan Barangay Hall and were being attended to by barangay and city officials.
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Quoting sunlinepr:


Yap, just one moderate shake. My wife was sleeping and woke up from that shake... It was located in the Mona passage...

That's where the big one is expected...

There was a small one then the strong one and I see that they updated the map with 2 quakes....
Alright just checkin in.

Hopefully that big one doesn't occur anytime soon...
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Quoting TomTaylor:
Everything ok, sunline?


We are OK...., just one moderate shake. My wife was sleeping and woke up from that shake... It was located in the Mona passage...

That's where the big one is expected...

There was a small one then the strong one and I see that they updated the map with 2 quakes....
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Quoting sunlinepr:
I just jumped from the sofa and called my wife.... I just felt that 5.1 shake here....

Everything ok, sunline?
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I just jumped from the sofa and called my wife.... I just felt that 5.1 shake here....

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Quoting JNCali:
ok... so we get a warmer arctic which results in cooler lower latitudes.. which will in turn be sending cooler air than normal back up to the arctic.. which should result in a cooler arctic.. depending of course on the activity levels of: sunspots, HAARP and aunt Julias back yard ant colony.. what am I missing here?? (jr. highers BEHAVE)


The arctic is warming faster than the mid-latitudes, but the mid-latitudes are not actually cooling, they are still warming.

The warm arctic cold continent thing Jeff was talking about has to do with the arctic oscillation, and not necessarily climate change. Also, the cooler air over the mid-latitudes is anomalously cool for that area, however if it were pushed northward it would not cool the arctic since the average temperature there is much cooler meaning it would still be warmer than normal.
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Massive outage as storm batters France

A STORM has battered north-western France, leaving hundreds of thousands without power, disrupting rail traffic and grounding a ship that spilled oil off the coast of Brittany.

There were no immediate reports of serious injuries or significant damage as storm Joachim moved further inland to Switzerland and Germany.

Interior Minister Claude Gueant said France had escaped largely unscathed from the storm.

"It seems there have been no victims," he said, adding that "a certain number" of people living in low-lying areas in Brittany had been evacuated because of the storm.

Officials said 400,000 homes had lost electricity, mainly in the west of the country. By mid-day, the number of homes without electricity had fallen to 330,000 as workers scrambled to restore electricity infrastructure.

Read more: http://www.news.com.au/breaking-news/massive-outag e-as-storm-batters-france/story-e6frfku0-122622449 4207#ixzz1gln49Sqh
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Quoting OrchidGrower:


SW Florida here as well; marveling at how warm it's been so far this month. Since I moved here for gardening, I am one happy camper about this warmth -- but it sure has been rainless here in the Cape!

Seems to me the buzz when fall started was how we were so likely to have another winter & spring identical to the last one, because of the return of La Nina. But right away, the snows in Colorado -- so opposite of last fall -- told me that something was different. Watching all the rain and snow in SoCal, and the warmth we're having here in SoFla, makes me think this winter will be different, which is fine with me! I'd love a warm winter for a change, not to mention no repeat of last spring's tornadoes for the Mid-South, where so many of my relatives live.

Cheers!


Another SWFL resident here (across the way in Lehigh Acres). My wife has been "complaining" that it just doesn't feel like Christmas here. I tend to agree. Highs in the 80s, just doesn't feel right.

I am thankful, though, that we dodged hurricane season here.
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86. Skyepony (Mod)
I was looking at the monsoonal trough down there in the SW Caribbean. It does at times get to be a semi-ingrained feature this time of year, flooding Columbia...especially when La Niña is in play.

Looking at 850 vort the CAtl swirl is much more prominent. Attached to a front, surface map has it at 1007mb. A bunch of sinking air is threatening it..Shear is closing in..it's in a hostile spot.

Caribbean blob is living on La Nina enhanced divergence aloft. If it stays shallow shear is light..above that, looks pretty hostile.

No surprise the enhanced divergence either.. ESPI fell .20 the last few days to -1.02. this tells La Nina is strengthening again.. Columbia has been feeling it all week with landslides. Shouldn't be long til TX dries out again.
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Quoting Ameister12:

170-180 knots? Wow! That's extremely impressive.


195-210 mph. Extremely impressive indeed.
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Quoting TropicalAnalystwx13:
Same difference guys.
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83. Skyepony (Mod)
Oceansat caught the CATL swirl..not quite closed..
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82. Skyepony (Mod)
ASCAT mostly missed..

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81. Skyepony (Mod)
I don't know how Windsat caught this.. it's been absolutely ailing, last I read was limited use maybe can't get enough sun.. Maybe they save the battery & waited til it get to where they could catch something of interest got this & Sendong today & not much else.

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Quoting TropicalAnalystwx13:
Of course it wasn't a Category 5 hurricane at peak intensity.

Sarcasm Flag: ON

Igor was just handsome.
Member Since: August 14, 2010 Posts: 10 Comments: 17856
Quoting Grothar:


Don't you ever pay attention to anything I taught you?
:)


Haha :)
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Quoting TropicalAnalystwx13:

Floyd had many 140 knot wind reports, and, as for Lenny...They found wind report(s) of 170-180 knots. I don't understand why they wouldn't upgrade.

170-180 knots? Wow! That's extremely impressive.
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ok... so we get a warmer arctic which results in cooler lower latitudes.. which will in turn be sending cooler air than normal back up to the arctic.. which should result in a cooler arctic.. depending of course on the activity levels of: sunspots, HAARP and aunt Julias back yard ant colony.. what am I missing here?? (jr. highers BEHAVE)
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Of course it wasn't a Category 5 hurricane at peak intensity.

Sarcasm Flag: ON

Member Since: July 6, 2010 Posts: 113 Comments: 32875
"Shoulda been" Category 5 Hurricanes

Floyd


Lenny


Igor
Photobucket
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Quoting NCHurricane2009:


On WXgeekVA's behalf...I can't deny that it is an interesting feature...but until the TAFB puts a surface low on the ITCZ in this region...I don't think its going to become a tropical cyclone....


I don't either,just a bunch of clouds in the Caribbean.
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Quoting Grothar:


I didn't say it was close to a depression WXgeekVa said it. Blame it on him. All I did was post an image say it had convection. LOL


On WXgeekVA's behalf...I can't deny that it is an interesting feature...but until the TAFB puts a surface low on the ITCZ in this region...I don't think its going to become a tropical cyclone....
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Quoting PensacolaDoug:
Re: 36


I'm glad you got that off of your chest.
Merry Christmas.

Yeah you to.
Member Since: August 14, 2010 Posts: 10 Comments: 17856
Quoting NCHurricane2009:


Its not close to a tropical depression....the only surface low pressure feature in the region is the ITCZ. At best there is a mid-level low pressure system, but no distinct low pressure at the surface...

However...this is an interesting feature for the month of December caused by a highly amplified upper ridge over the Caribbean Sea enhancing the outflow of the ITCZ over this area.


I didn't say it was close to a depression WXgeekVa said it. Blame it on him. All I did was post an image say it had convection. LOL
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70. Inyo
Quoting TomTaylor:
With regards to the first section of Dr. Masters blog regarding arctic warming, I would think a far bigger cause for a slowing down of winds in the mid latitudes allowing for increased amplification would be the weaker pressure gradient between the arctic and the mid latitudes.

Looking at current global temperature trends it is apparent that the arctic region has been warming much faster than the mid-latitude regions. This means that the temperature difference between the arctic and the mid-latitudes is less which creates a weaker pressure gradient between the two regions. The weaker pressure gradient yields weaker winds between the regions. Weaker winds create a weaker centrifugal force, allowing for air masses or wind to curve or bend more, which creates more amplified wavelengths.

While the lack of sea ice would mean more surface friction for airmasses, I can't see this effect being very significant beyond the planetary boundary level (point where wind is no longer effected by the frictional effects of the Earth's surface roughly around 5,000 ft). Therefore, it most sense to me that the decrease in temperature difference (creating a weaker pressure gradient) is mostly responsible for the lighter winds and more amplified pattern.


The change in friction isn't the main issue, the moderation of temperatures by open water (and possible changes in ocean currents) are the main issue
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Philippine Atmospherical Geophysical Astronomical Services and Administration
Tropical Cyclone Bulletin #9
TROPICAL STORM SENDONG (WASHI)
11:00 AM PhST December 17 2011
=================================

Tropical Storm "SENDONG" has intensified slightly and is now traversing Sulu Sea towards Palawan

At 10:00 AM PhST, Tropical Storm Sendong located at 9.3°N 121.6°E or 180 km west of Dumaguete City has 10 minute sustained winds of 40 knots with gusts of 50 knots. The cyclone is reported as moving west northwest at 15 knots.

Signal Warnings
===============

Signal Warning #2
-----------------

Luzon region
============
1.Palawan

Visayas region
==============
1.Southern Negros

Mindanao region
==============
1.Zamboanga del Norte

Signal Warning #1
----------------

Luzon region
============
1.Cuyo island

Visayas region
=============
1.Southern Cebu
2.Siquijor
3.Northern Negros

Mindanao region
==============
1.Zamboanga del Sur
2.Misamis Occidental

Additional Information
========================
All signals elsewhere are now lowered.

Residents in low lying and mountainous areas under Public Storm Warning Signals are alerted against possible flash floods and landslides. Likewise, those living in coastal areas are alerted against big waves or storm surges generated by this tropical cyclone.

Estimated rainfall amount is from 10-20 mm per hour (heavy) within the 300 km diameter of the Tropical Storm.

Fishing boats and other small sea crafts are advised not to venture out into the sea.

The public and the disaster coordinating councils concerned are advised to take appropriate actions and watch for the next bulletin to be issued at 5 PM today and the hourly updates.
Member Since: May 24, 2006 Posts: 52 Comments: 47091
I have been also noting lately an unusual string of extratropical lows this December that looked interesting for subtropical development....

The latest one is present at 52.5W...25N as I right this....I'd be watching this featuere as well for subtropical development...
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Quoting Grothar:


We have convection.



Its not close to a tropical depression....the only surface low pressure feature in the region is the ITCZ. At best there is a mid-level low pressure system, but no distinct low pressure at the surface...

However...this is an interesting feature for the month of December caused by a highly amplified upper ridge over the Caribbean Sea enhancing the outflow of the ITCZ over this area.
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Quoting caneswatch:


I thought it was pronounced E-GORE?


Don't you ever pay attention to anything I taught you?
:)
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Same difference guys.
Member Since: July 6, 2010 Posts: 113 Comments: 32875
Quoting Grothar:



Froderick told me it was pronounced EYE-gor.


I thought it was pronounced E-GORE?
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Quoting Articuno:

I thought it was EE-GORE.



Froderick told me it was pronounced EYE-gor.
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With regards to the first section of Dr. Masters blog regarding arctic warming, I would think a far bigger cause for a slowing down of winds in the mid latitudes allowing for increased amplification would be the weaker pressure gradient between the arctic and the mid latitudes.

Looking at current global temperature trends it is apparent that the arctic region has been warming much faster than the mid-latitude regions. This means that the temperature difference between the arctic and the mid-latitudes is less which creates a weaker pressure gradient between the two regions. The weaker pressure gradient yields weaker winds between the regions. Weaker winds create a weaker centrifugal force, allowing for air masses or wind to curve or bend more, which creates more amplified wavelengths.

While the lack of sea ice would mean more surface friction for airmasses, I can't see this effect being very significant beyond the planetary boundary level (point where wind is no longer effected by the frictional effects of the Earth's surface roughly around 5,000 ft). Therefore, it most sense to me that the decrease in temperature difference (creating a weaker pressure gradient) is mostly responsible for the lighter winds and more amplified pattern.

edit: nvm, didn't even read his entire blog
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Quoting Grothar:


It is pronounced EYE-gor.

I thought it was EE-GORE.
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Quoting yqt1001:
Lenny and Floyd both had recon confirmed 135kts winds, while Floyd and Igor had satellite estimates of 140kts winds. Igor I guess has hte highest chance of actually being a category 5 hurricane, but we will never know, and changes to TCR's especially when it comes to maximum winds/lowest pressure rarely happen.

Floyd had many 140 knot+ wind reports, and, as for Lenny...They found wind report(s) of 170-180 knots. I don't understand why they wouldn't upgrade.
Member Since: July 6, 2010 Posts: 113 Comments: 32875
Lenny and Floyd both had recon confirmed 135kts winds, while Floyd and Igor had satellite estimates of 140kts winds. Igor I guess has the highest chance of actually being a category 5 hurricane, but we will never know, changes to TCR's especially when it comes to maximum winds/lowest pressure rarely happen.
Member Since: November 19, 2010 Posts: 1 Comments: 1286
TAWX13's list of thought Category 5 Atlantic hurricanes:

- Floyd
- Lenny
- Igor


Figure 1: Dvorak imagery of Hurricane Lenny as a strong Category 4 hurricane, although I believe it reached its peak winds of 160 mph at this time.
Member Since: July 6, 2010 Posts: 113 Comments: 32875
Quoting Grothar:


It is pronounced EYE-gor.

Yes.
Member Since: July 6, 2010 Posts: 113 Comments: 32875
Quoting TropicalAnalystwx13:
Igor looks like an absolute monster in this image. Of course, the fact that it was the most destructive tropical cyclone in Newfoundland history DOES make it a monster.



It is pronounced EYE-gor.
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Quoting WxGeekVA:


Little more convection and I'd say we have a TD on our hands...


We have convection.

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Quoting Ameister12:

Here's some color.


Little more convection and I'd say we have a TD on our hands...
Member Since: September 3, 2011 Posts: 13 Comments: 3477
Igor looks like an absolute monster in this image. Of course, the fact that it was the most destructive tropical cyclone in Newfoundland history DOES make it a monster.

Member Since: July 6, 2010 Posts: 113 Comments: 32875
Quoting Grothar:



Color, Ameister, Color!!


Here's some color.
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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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