Friday 8 August 2014

Wild weather

Terrible Thunderstorms of Fire Over Canada as Arctic Territory Continues Record Burn

7 August, 2014

They call them pyrocumulonimbus. In layman’s terms — fire thunderstorms.

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At the surface, a very large wildfire covering tens of square miles or more can produce quite a lot of heat. The smokey column cast off by the burning blaze rises, generating lift in the atmosphere even as it seeds the air with smoke — nuclei to which water droplets can adhere and from which clouds can form. The rising column contacts water vapor, pushing a vast head of it upward. As this heat-driven column hits the upper reaches of the troposphere, it cools, and the water vapor condenses to the readily available smoke aerosols.

This process produces what is called a pyrocumulus cloud or a fire cloud — a smoke and heat fed version of the normal and far less ominous puffy cumulus clouds we are so accustomed to seeing during summer afternoons. In the pyrocumulus, if the updraft is intense enough, if the fire beneath the cloud strong enough, it erupts into a pyrocumulonimbus — a fire thunderstorm rife with lightning and, if the firefighters are lucky, rain as well.


On August 5, 2014, NASA got an amazing shot of a pyrocumulonimbus cloud exploding over the massive and anomalous wildfires still raging in Arctic Canada. See that horrific boiling cloud stack above fire and smoke in the center-left of the image below? That’s a fire thunderstorm:
Pyrocumulonimbus
(Explosive pyrocumulonimbus cloud near Great Slave Lake on August 5 of 2014. Marked off red areas in the image indicate fire boundaries for individual fires. For reference, Buffalo Lake in the lower left corner is about 35 miles long from end to end. Image source:NASA.)
Dark Carbon Delivery Mechanism

NASA keeps a close watch on fire thunderstorms for a number of reasons. First, they are an indication of the heat updraft intensity rising off the fire beneath. And though they can result in beneficial rains, the storms are, many times, dried out by an over-abundance of smoke. As a result, a dry fire thunderstorm can add to fire hazard by casting off bolts of fire-setting lightning while begrudgingly holding back their moisture load.

Lastly, and perhaps most hauntingly, the fire thunderstorm is a delivery mechanism for black and brown carbon aerosols to the stratosphere, where they can do considerable damage. For if the updraft in the fire thunderstorm is powerful enough, water vapor droplets laden with heat intensifying dark carbon can break the troposphere boundary and enter the stratosphere. There, these dark aerosols trap heat and intensify global warming.

NASA studies have shown that dark aerosols in the stratosphere can have a global warming potential impact up to a million times that of a similar volume of CO2, so even a small amount lofted by fire thunderstorms could have a substantial effect. And the recent very, very intense fires in the Arctic region may well be providing an ominous and very widespread mechanism for just such a dangerous delivery.

Fire Thunderstorms Over Record Arctic Burn Zone

The region where this fire thunderstorm erupted on August 5 is experiencing what is likely the most intense Arctic burn Canada has ever seen. Since the start of this year, and as of August 6, about 2,850,000 hectares (11,000 square miles) have burned in the Arctic Northwest Territory (NWT) alone. This burn area so far for this one territory is almost twice that for the whole of Canada during an average year through early August. For the NWT, it represents an epic burning more than 15 times that of the 15 year average (which is usually 185,000 hectares by this time of year).

To say that such a major burn for an Arctic region normally resistant to wildfires is extraordinary may well be an understatement. The blazes this year cast off smoke that covered much of the North American Continent, crossed Greenland and has ridden weather systems around the globe. Many fires have burned non-stop for more than a month, burning the soil and thawed permafrost once the forest fuels are exhausted.

Climate models show an increased prevalence of Arctic wildfires as human warming continues to advance into the Arctic this Century. As of the mid 2000s and throughout this decade, we have seen very intense wildfires raging in Arctic Canada, Alaska, Scandinavia, and Siberia.
Siberian Wildfires August 6
(Massive wildfires still burning in Siberia on August 6, 2014. For reference, bottom edge of frame is about 300 miles. Image source: LANCE-MODIS.)
That these fires are an amplifier to human driven warming is probably a given. They dump extra CO2 and methane into the atmosphere, they burn both the more recent forest carbon store and the far older store in the soil, they break the permafrost cap, opening up new fuels for fires in subsequent years and providing avenues for methane and CO2 release, they dump dark carbon over low albedo surfaces such as ice sheets and sea ice, and they produce fire thunderstorms with the potential to inject dark carbon into the stratosphere.

While taking into account the entire Arctic system feedback to human caused climate change will likely be a monumental task, the mechanism of Arctic wildfires to tap and deliver the massive land-based Arctic carbon store to the atmosphere in various ways may be one of the critical elements in the overall feedback system. One that to any rational observer appears to be energetically emerging now. An expanding Arctic outburst of summer smoke and flame that is terrifying to watch.

Links:


UK severe weather warnings 

as hurricane Bertha crosses 

Atlantic

Almost month's rain could fall in few hours in parts of south on Sunday, with forecasters warning of flooding and strong winds


7 August, 2014

Forecasters have warned that parts of Britain can expect almost a month's rainfall in the space of a few hours and strong winds, especially in the south, on Sunday, with the risk of flooding as the remains of hurricane Bertha reach this side of the Atlantic.

The Met Office has issued a severe weather warning for rain for Sunday covering Wales and southern England, bringing at least a temporary end to a glorious summer. "There is the potential for widespread rainfall totals of more than 50mm and coastal gusts of over 60mph, along with large waves," said the Met. "However, the system may pass harmlessly to the south of the country or spread heavy rain even further north, and the public are advised to keep up to date with warnings."

The average rainfall for the whole of August in England is 69mm.

The Met has been tracking Bertha for the past few days, trying to determine its strength and direction. It is a notoriously difficult task and the forecasts have to be adjusted according to the data. "The transition from a tropical to an extra-tropical feature is a particularly hard one to forecast with confidence, and computer models continue to differ in the location and intensity of the resulting depression, which is expected to pass over, or close to, the UK from early on Sunday," the Met said.

On Wednesday, forecasters thought Britain was unlikely to suffer serious after-effects from the hurricane, which battered the Caribbean islands with gusts of more than 90mph, leaving thousands of homes without power. They said it was debatable whether what would arrive was even ex-Bertha as the storm weakened to such an extent as it crossed the Atlantic.

On Thursday, however, they changed tack, warning of heavy rain and a possible risk of flooding.

"On Sunday and Monday, a combination of high spring tides and strong westerly winds brings a possible risk of flooding to the south-west coast of England and along the Severn estuary, while heavy rain may also lead to localised surface water flooding in parts of southern and central parts of England," said Craig Woolhouse, flood risk manager at the Environment Agency.

"However, the forecast remains uncertain so we advise people to regularly check the flood risk situation over the next 48 hours."

On Friday, parts of Britain will see some heavy rain that is not linked to Bertha.

Bertha, the second hurricane of the 2014 Atlantic hurricane season, began as a tropical storm on 31 July about 275 miles east-southeast of Barbados. It brought some welcome rainfall to drought-suffering parts of Puerto Rico, the Virgin Islands, and eastern Hispaniola.

Much of Puerto Rico picked up at least 25mm of rain, with some interior mountainous locations estimated to have topped 254mm, with reports of partial road collapses.

Bertha's impact on the US took the form of high surf and "rip" currents that move directly away from the shore. One man drowned due to rip currents Florida.

Hawaii prepares for first direct hit from hurricane in 22 years as second storm looms
The Big Island of Hawai’i is bracing for a double whammy of hurricanes to make landfall between Thursday and Monday, according to the National Weather Service. The last time the archipelago took a direct hit from a hurricane was 1992.


RT,
7 August, 2014

Iselle, a Category 1 storm, is forecast to arrive on Hawai’i Thursday night local time, then weaken and continue on to the rest of the islands by Friday, according to Weather.com. The storm defied expectations that it would weaken to a tropical storm over the course of the day Wednesday. Iselle is roughly 300 miles east-southeast of Hilo, on the island’s eastern corner. It is moving quickly, at 15-20 mph.

"The real effects will probably be felt on the Big Island starting around noon" (6 p.m. ET) on Thursday, Norman Hui, a National Weather Service (NWS) meteorologist in Honolulu, told USA TODAY. "The worst of it will be tonight. This storm is holding together pretty well."

The storm is currently weakening, and forecasters are unsure whether it will make landfall as a hurricane or a tropical storm, Weather.com reported. At 7 a.m. Hawaiian time (5 p.m. GMT), Iselle had maximum sustained winds of 80 mph, placing it in the middle of the Cat-1 range (74-95 mph) on the Saffir-Simpson scale, according to the Central Pacific Hurricane Center (CPHC).

Even still, Iselle is expected to bring heavy rains totaling 5 to 8 inches, winds gusting up to 85 mph, and flooding, while waves could grow up to 28 feet, according to the NWS.

It’s a fairly potent hurricane by Hawaiian standards,” said Weather Channel meteorologist Kevin Roth.

Meanwhile, forecasters are also keeping an eye on Hurricane Julio, currently a Cat-2 (defined as winds 96-110 mph). That storm is lurking over 1,000 miles each of the Hawaiian archipelago, with sustained winds of 100 mph. Its current track has it hitting the islands late Sunday or Monday, but it is too far away to make a firm prediction of its course, Hui said.

With the close proximity of the two major storms, as well as a 4.3-magnitude earthquake that struck seven miles (11 km) west northwest of Waimea (and 50 miles from Hilo) on Thursday morning, residents are stocking up on water and non-perishable items.

Honolulu school teacher Gina Nakahodo told Reuters she had felt calm until she reached the empty water aisle of her local grocery store early on Tuesday.

"We've had so many storms that have passed us by, but with these two back to back you begin to worry. Then all of the sudden the aisles are empty and there's no water and it makes your heart pound a little," Nakahodo said.

Willis Sanchez leaves the local hardware store with sheets of plywood to board up his windows as a hurricane and a tropical storm approach the Hawaiian islands, in Mililani, Hawaii, August 5, 2014.(Reuters / Hugh Gentry)Willis Sanchez leaves the local hardware store with sheets of plywood to board up his windows as a hurricane and a tropical storm approach the Hawaiian islands, in Mililani, Hawaii, August 5, 2014.(Reuters / Hugh Gentry)

Hurricanes ‒ especially major ones ‒ are rare on the Hawaiian islands. The last direct hit came from Iniki in 1992, the deadliest and by far the costliest hurricane to ever strike the state. Adjusted for inflation, Iniki caused roughly $3 billion in damages, Weather.com reported. More than 14,000 homes were affected, with 1,421 destroyed and 5,152 with major damage, and four people died.

While wind was the cause of most of the damages, storm surge and waves obliterated many structures along Kauai’s southern shore," Weather.com said. “The other main Hawaiian Islands including Oahu were affected by Iniki, mainly in the form of high surf but also with some wind damage, but Kauai took the full force of the hurricane.”

The archipelago was only hit twice before Iniki’s arrival, by Iwa in 1982 and by Dot in 1959 (just before Hawaii became a state); both were Category 1 storms. Iwa had 90-mph winds and caused $312 million in damages on the islands of NiÊ»ihau, KauaÊ»i and OÊ»ahu. One person died. Dot caused $6 million worth of destruction, and indirectly led to two deaths, according to the San Francisco Gate.

Because of the infrequency of the major storms, meteorologists don’t know how the mountains on Hawai’i will affect Iselle’s impact on the island.

"The Big Island has two peaks of up to 14,000 feet. If the hurricane makes a direct hit over the Big Island, how much of a blocking effect that has we don't know," Ray Tanabe, acting director for the NWS in the Pacific Region, told Reuters.

Mike Cantin, another NWS meteorologist, told the Associated Press that the Big Island’s terrain should help break up the storm’s strength, weakening it to a tropical storm as it heads on to Maui and Oahu. "The volcanoes on the Big Island will do a number on the system," he said.

The biggest problem with the terrain ‒ and the state’s distance from the mainland ‒ is its potential for impacting disaster relief efforts.

"With Hawaii's remoteness, it could be as long as a week before a full disaster relief operation can be initiated," the Honolulu Department of Emergency Management said in a statement.

HDEM has released a document of frequently asked questions for residents to prepare for the storms. The department is recommending residents to prepare a seven-day disaster supply kit.

4.5 Earthquake Strikes 

Hawaii as Hurricane Iselle 

Looms


http://blog.weathernationtv.com/2014/08/07/4-5-earthquake-strikes-hawaii-as-hurricane-iselle-looms/


As residents of Hawaii — especially the Big Island — prepare for the late Thursday landfall of Hurricane Eselle, they’re dealing with another natural hazard as well. A 4.5 earthquake struck on the island of Hawai’i around 6:24 a.m. local time, jolting already on-edge residents.

The quake, centered about 7 miles west-northwest of Waimea, was relatively shallow — only about 9.5 miles below the surface. At this point no damage is being reported and the Pacific Tsunami Warning Center tweeted that no tsunami warning would be issued.

No from local 4.2 earthquake in the Kohala Region of the Big Island, Hawaii. http://ptwc.weather.gov/?region=2&id=hawaii.EQIHWX.2014.08.07.1626 
Hawaii is no stranger to seismic activity, as the island state sits on top of a mid-tectonic plate plume of magma. Movement of subterranean magma is most often the cause of earthquakes in Hawaii, since it’s so far removed from fault lines. On average, Hawaii has about 50 earthquakes per year. Making the Aloha State the third most seismically active state, only behind Alaska and California.

Kiluea, which is also on the Big Island, is the most active volcano on Earth and has been erupting since January 3, 1983.




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