Elders meet with the mayor and the governor of Gao in the city of Gao, Northern Mali, Wednesday Jan. 30, 2013. All tribe leaders were called to attend the meeting in an effort to avoid vengeance attacks following the arrival of French and Chadian troops in the area, ending 10-months of sharia laws. (AP Photo/Jerome Delay)

Malian women laugh as one pulls her veil saying she doesn't need it any longer in the central market in Gao, Northern Mali, Wednesday Jan. 30, 2013. The mission by French troops scored another success in its effort to dislodge the al-Qaida-linked militants from northern Mali, and freed from Islamic rule over the weekend, women started coming out wearing bright colors, makeup and jewels, after 10 month of black veils and sharia laws. (AP Photo/Jerome Delay)

SEVARE, Mali (AP) — French forces met no resistance Wednesday in Kidal, the Islamists' last major town, as the two-week-old mission scored another success in its effort to dislodge the al-Qaida-linked militants from northern Mali.

The capture of Kidal came just days after French and Malian forces retook two other provincial capitals — Gao and Timbuktu — that also had been under harsh Islamic rule for nearly 10 months.

"Nobody questions France's rapid deployment but the ability to hold on to the cities and territory is an immense challenge. It is not clear how they will be able to sustain the recent gains," said Alex Vines, head of the Africa program at Chatham House.

"The Islamist extremists have not been defeated; they have melted into the heat haze of the desert."

Many fear the Islamists now will attempt to hide among civilian populations in small outlying villages, only to return and attack the weaker African forces once the French are gone.

The Islamists are believed to have an elaborate system of caves and other desert hideouts that they have constructed over the last year as momentum for a West African regional military intervention stalled.

The Islamist fighters fired on French forces when they arrived in Gao, though the militants had deserted Timbuktu by the time forces arrived there on Monday, damaging the airport's runway in acts of vengeance as they fled.

Haminy Maiga, the interim president of the Kidal regional assembly, said French forces also met no resistance when they arrived late Tuesday in Kidal.

"The French arrived at 9:30 p.m. aboard four planes, which landed one after another. Afterwards they took the airport and then entered the town, and there was no combat," said Maiga, who had been in touch with people in the town by satellite phone as all the normal phone networks were down.

"The French are patrolling the town and two helicopters are patrolling overhead," he added.

In Paris, French army Col. Thierry Burkhard confirmed that the airport was taken overnight and described the operation in Kidal itself as "ongoing." France's defense minister said bad weather was hampering the troops' progress out of the airport.

Maiga said fighters from the National Movement for the Liberation of Azawad — a secular Tuareg group that once battled alongside the Islamists for control of the north — had left Kidal as of Wednesday. Azawad is what the Tuaregs call their homeland in northern Mali.

France, the former colonial ruler, began sending in troops, helicopters and warplanes on Jan. 11 to turn the tide after the armed Islamists began encroaching on the south, toward the capital. French and Malian troops seized Gao during the weekend, welcomed by joyous crowds. They took Timbuktu on Monday.

"Now it's up to African countries to take over," French Foreign Minister Laurent Fabius told Le Parisien newspaper. "We decided to put the means — in men and supplies — to make the mission succeed and hit hard. But the French aspect was never expected to be maintained. We will leave quickly."

In Gao's main market, thousands of women returned to work on Wednesday without the black veils required by the Islamists. They wore vibrant patterned fabrics and sported makeup.

"We are free today, we are free," said Fatima Toure, a Gao resident.

Back from exile, the mayor and governor of Gao met with community elders to chart the best measures for returning life to normal.

The elders presented two cows to the authorities and a representative of the French army in gratitude for their work in liberating Gao.

While most crowds in the freed cities have been joyful, months of resentment toward the Islamists bubbled into violence in Gao.

Video footage filmed by an amateur cameraman and obtained by The Associated Press shows a mob attacking the symbol of the extremists' rule, the Islamic police headquarters.

Some celebrate cheering "I am Malian," while others armed with sticks and machetes attack suspected members of the Islamist regime. The graphic images shot Saturday show the mob as they mutilate the corpses of two young suspected jihadists lying dead in the street.

There are 3,500 French troops involved in the operation and 2,900 Africans, according to the latest figures from the French Defense Ministry.

Mali's military was severely affected by a military coup last year coup and has a reputation for disorganization and bad discipline. Malian soldiers have been accused of fatally shooting civilians suspected of links to the Islamists. The military has promised to investigate the allegations.

___

Andrew Meldrum in Johannesburg; Baba Ahmed in Segou, Mali; Lori Hinnant in Paris; and Andrew Drake and Jerome Delay in Gao, Mali contributed to this report.

Forecast high temperatures on Monday, Jan. 21, from the GFS computer model.
Click to enlarge the image. Credit: Weatherbell

This phenomenon, known as a “sudden stratospheric warming event,” started on Jan. 6, but is something that is just beginning to have an effect on weather patterns across North America and Europe.

While the physics behind sudden stratospheric warming events are complicated, their implications are not: such events are often harbingers of colder weather in North America and Eurasia. The ongoing event favors colder and possibly stormier weather for as long as four to eight weeks after the event, meaning that after a mild start to the winter, the rest of this month and February could bring the coldest weather of the winter season to parts of the U.S., along with a heightened chance of snow.

Sudden stratospheric warming events take place in about half of all Northern Hemisphere winters, and they have been occurring with increasing frequency during the past decade, possibly related to the loss of Arctic sea ice due to global warming. Arctic sea ice declined to its smallest extent on record in September 2012.

An Arctic cold front was sliding south from Canada on Friday, getting ready to clear customs at the border on Saturday and Sunday, bringing an icy chill to areas from the Plains states through the Mid-Atlantic by early next week, including what promises to be a chilly second inauguration for President Obama. Temperatures in Washington on Monday are expected to hover in the low 30s, only a touch milder than Obama’s first inauguration, when the temperature was 28°F.

Reinforcing shots of cold air are likely to affect the Upper Midwest, Great Plains and into the East throughout February, with some milder periods sandwiched in between.

Sudden stratospheric warming events occur when large atmospheric waves, known as Rossby waves, extend beyond the troposphere where most weather occurs, and into the stratosphere. This vertical transport of energy can set a complex process into motion that leads to the breakdown of the high altitude cold low pressure area that typically spins above the North Pole during the winter, which is known as the polar vortex.

The polar vortex plays a major role in determining how much Arctic air spills southward toward the mid-latitudes. When there is a strong polar vortex, cold air tends to stay bottled up in the Arctic. However, when the vortex weakens or is disrupted, like a spinning top that suddenly starts wobbling, it can cause polar air masses to surge south, while the Arctic experiences milder-than-average temperatures.

During the ongoing stratospheric warming event, the polar vortex split in two, allowing polar air to spill out from the Arctic, as if a refrigerator door were suddenly opened.

An animation showing the evolution of the stratospheric warming event. The contours show absolute heights and the shading are height anomalies in the middle stratosphere, or about 16 miles above the surface. The height anomalies are a good proxy for temperature anomalies in the stratosphere with red representing high heights or warm temperatures and blue low heights or cold temperatures. You can see at the beginning of the loop a cohesive polar vortex along the coast of Northern Eurasia and then this area of higher heights or warm temperaturs rush poleward from Siberia into the polar vortex splitting it into two pieces, one over Eurasia and one over North America. The dramatic rise in heights or temperatures over the Pole is the sudden stratospheric warming. The result is that pieces of the polar vortex move equatorward and with it the associated cold temperatures. Usually something similar occurs in the troposphere in the ensuing weeks. Credit: AER/Justin Jones.

When the sudden stratospheric warming event began in early January, that signaled to weather forecasters that a cool down was more likely to occur by the end of the month, since it usually takes many days for developments in the stratosphere to affect weather in the troposphere, and vice versa.

“For reasons I don’t think we fully understand, the changes in the circulation that happen in the stratosphere [can] descend down all the way to the Earth’s surface,” said Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research (AER) in Massachusetts.

As the polar stratosphere warms, high pressure builds over the Arctic, causing the polar jet stream to weaken. At the same time, the midlatitude jet stream strengthens, while also becoming wavier, with deeper troughs and ridges corresponding to more intense storms and high pressure areas. In fact, sudden stratospheric warming events even make so-called “blocked” weather patterns more likely to occur, which tilts the odds in favor of the development of winter storms in the U.S. and Europe.

Cohen was the lead author of a 2009 study that found that sudden stratospheric warming events are becoming more frequent, a trend that may be related to an increase in fall snow cover across Eurasia. The increase in snow cover has in turn been tied to the rapid loss of Arctic sea ice, since the increase in open water in the fall means that there is more atmospheric moisture available to fall as rain or snow.

Cohen and his colleagues at AER have been using an index of Eurasian snow cover during the month of October in order to make seasonal weather forecasts for the following winter, and he said that by using this technique, they successfully predicted the ongoing stratospheric warming event 30-days in advance.

“As far as I know this is a first and has huge implications for intraseasonal predictions,” he said.

Computer model forecast for February, showing widespread cooler than average conditions in much of the U.S.
Click to enlarge the image. Credit: Weatherbell.

Cohen’s research has also pointed to stratospheric warming events as one of the reasons why the second half of recent winters in the Northern Hemisphere have turned out to be colder than the first half.

“Scientists about a decade ago predicted that stratospheric warmings would become less frequent with climate change, however, just the opposite has happened and they have become more frequent. There is a positive trend in stratospheric warmings since the turn of the century and I have argued this is contributing to more severe winters,” he said.

When the vortex becomes dislodged from the pole, Cohen said, it can lead to a flow of air that is more north to south than west to east. “So when the warm air rushes the pole it displaces the cold air over the pole and forces it equatorward,” Cohen said.

This has major implications for U.S. winter weather.

High temperatures in North Dakota and Minnesota may not make it above zero Fahrenheit on Sunday and Monday. If Minneapolis records a high temperature below zero it will end its record-breaking streak of four years without such an occurrence. By Tuesday, the cold air will have spilled into Kentucky and Maryland as well as New England. And the long-range outlooks suggest that February is going to be a colder-than-average month from the Upper Midwest to the East Coast, although there may be brief breaks from the cold depending on the prevailing storm track.

Anthony Artusa, a seasonal climate forecaster at the National Oceanic and Atmospheric Administration (NOAA), said the cold air spilling southward for the inauguration may mark the beginning of a long-lasting cold period that is related to the stratospheric warming event. “It does look like this could be the early effects of it,” he said during a conference call with reporters on Thursday.

Related Content:
Winter Outlook Offers Hope For Skiers and Boarders
A Closer Look At Arctic Sea Ice Melt and Extreme Weather
Visualizing 2012's Record Arctic Sea Ice Melt
Warming Arctic May Be Causing Cooler Winters in Eastern U.S., Europe

Follow the author on Twitter @afreedma or @ClimateCentral. We're also on Facebook & other social networks.