Saturday, October 25, 2014

Kelvin-Helmholtz Billow Clouds Spotted in Thornton, Colorado

In addition to the solar eclipse, a special sight was spotted in the sky Wednesday over Thornton, Colorado.
Though it looks like someone painted the sky with breaking ocean waves in the collection of photos above, there's a very good atmospheric explanation for what is really happening. The rolling, wave-like cloud formations are called Kelvin-Helmholtz clouds. Sometimes they are also called billows. They are named for scientists Lord Kelvin and Hermann von Helmholtz, who discovered the process by which they form.
Severe Weather Expert Dr. Greg Forbes of The Weather Channel says, "They are the atmospheric equivalent of those great breaking waves that you sometimes see on the ocean."

These breaking atmospheric waves occur in an environment with a large amount of vertical wind shear and stable air. Wind shear is a change in the speed and direction of winds as you go higher in the atmosphere.

In this case, winds at the top of the cloud layer are moving faster than the base of that same layer. This causes the top to crash downwards in a curling manner after it hits the stable layer above.

Friday, October 24, 2014

Greece Flooding, Caused By Slow-Moving Remnants of Hurricane Gonzalo, Covers Athens Streets

The storm that just won't quit is hammering Greece, and it won't be going anywhere for at least a couple of days. Heavy rain dumped on Greece Friday, flooding some roadways and creating travel problems in Athens, according to local reports. Word of significant flash flooding began in the Greek capital Friday afternoon.  The Greek Reporter says that at least 12 cars were trapped inside a flooded supermarket parking lot after the heavy storms hit. Initial reports state that dozens of households were flooded, and that anywhere from 20-30 cars were swept into a pileup Friday. Shopkeepers say damages from the flood may exceed 100,00 euros or $126,651. 
Meteorologists say the rainfall can be tied to the remnants of Hurricane Gonzalo.
"This cutoff low, so-called because it has become detached from the steering influence of the jet stream, contains some of the energy from what was once Hurricane Gonzalo," said senior meteorologist Jonathan Erdman. "While not necessarily indicative of a continuing, large-scale heavy rain threat, this stubborn upper-level low is forecast to remain swirling over the Aegean Sea and eastern Mediterranean Sea into much of next week."
The tropical system previously known as Gonzalo has tracked across thousands of miles, hitting the Caribbean before making landfall on Bermuda last Friday. Then, it traveled across the Atlantic and hit the United Kingdom, Belgium, the Netherlands and Scandinavia with bouts of rain and high winds. Now, it has sunk southeast and is expected to linger over the Balkan peninsula for several days. The system also dumped feet of snow in the Swiss and Austrian Alps. 

One of Sao Paulo’s Biggest Reservoirs Is Nearly Dry

Drought is taking its toll on the water system that quenches the thirst of Brazil’s largest city, Sao Paulo, to such a degree that it is visible to orbiting satellites. Sao Paulo is facing water rationing as the worst drought to hit the region in decades reduces reservoirs to muddy waters surrounded by cracked earth.  The Cantareira Reservoir System provides about half of the overall water to the city’s 20 million residents. But a series of months with below average rainfall have seen water levels plummet. NASA Landsat 8 images published by theNASA Earth Observatory show the precipitous decline of the Jaguari Reservoir, one of a handful that make up the system, from mid-August last year to early August this year.
Since the images were acquired, the water levels have only dropped further. As of Thursday, Sabesp, Sao Paulo’s water utility, reported that the Cantareira system was operating at only 3 percent of its capacity. That’s essentially considered “dead water,” which Sabesp has only been able to tap after building an extra 2 miles of pipeline to the reservoir’s center.
During the height of last year’s rainy season, which is December-February, the region around Sao Paulo saw deficits in excess of 15 inches according to data from the International Research Institute for Climate and Society (IRI). For this month, the watershed that the system covers has received only 18 percent of its normal monthly rainfall, a worrisome total on the cusp of the rainy season. But there’s a slight glimmer of hope for the peak of rainy season. IRI’s seasonal forecast for December-February shows the odds tipped slightly in favor of wetter conditions in parts of the region, which would help refill reservoirs and ease water restrictions.
In the long-term, climate change could further exacerbate Sao Paulo’s problems. A report released by the Intergovernmental Panel on Climate Change in late 2013 showed that if greenhouse gas emissions continue to rise, September-November are likely to become drier in the region. Some models indicate the rainy season could actually get slightly wetter by century’s end but there’s still a high degree of uncertainty associated with those projections. 

Earth Headed For its Hottest Year on Record After a Record-Warm September

September 2014 was Earth's warmest September on record, the period January - September was tied with 1998 and 2010 as the warmest first three-quarters of any year on record, and the past 12 months--October 2013 through September 2014--was the warmest consecutive 12-month period among all months since records began in 1880, said NOAA's National Climatic Data Center (NCDC) today. NASAalso rated September 2014 as the warmest September on record. If 2014 maintains the same temperature departure from average for the remainder of the year as was observed during January - September, it will be the warmest calendar year on record. September is the fourth time NOAA has ranked a 2014 month as the warmest on record; May, June, and August 2014 were also the warmest such months on record.

Tropical Depression Nine Dissipates

Small and weak Tropical Depression Nine dissipated over Mexico's Yucatan Peninsula Wednesday night, shortly after making landfall near 8 pm EDT Wednesday October 22, 2014 on the western shore of the peninsula. Mexican radar out of Sabancuy and satellite loops show that ex-TD 9 is bringing some heavy rains to the Yucatan Peninsula, Belize, Guatemala, and the adjacent waters, and this activity will continue into the weekend. By Saturday, some of the spin associated with TD 9 may emerge over the Western Caribbean, and we should carefully watch this area on Sunday and Monday for tropical cyclone development--though none of our reliable models were predicting development in their Thursday morning runs.

Invest 94L in Western Caribbean Little Threat to Develop

The remains of Tropical Depression Nine, which dissipated over Mexico's Yucatan Peninsula on Wednesday night, were moving offshore of Belize into the Western Caribbean on Friday morning. This disturbance is being labeled Invest 94L by NHC. Belize radar and satellite loops show that 94L has only a few poorly-organized clusters of heavy thunderstorms over the Yucatan Peninsula, Belize, Honduras, Guatemala, and the adjacent waters. None of our reliable models for predicting tropical cyclone genesis were predicting development of 94L in their Friday morning runs. A trough of low pressure connected to the large Nor'easter affecting the Northeast U.S. is bringing high wind shear of 15 - 25 knots to the Western Caribbean and is injecting dry air, which is discouraging development.

What will winter hold for drought-plagued California?

California really needs this winter to be a wet one.
The state is now at the beginning of the fourth year of one if its worst droughts on record. The drought has been fueled by a spate of disappointing winter rainy seasons that have left meager snowpacks and diminished reservoir levels, combined with record-warm temperatures that have driven demand for the increasingly precious resource, and spurred a series of conservation measures around the state.
Hopes that the coming winter could finally bring some relief were raised when the first murmurs of an impending El Niñobegan to emerge in March. The climate phenomenon can be associated with amped up rains in the southern part of the state, and so the words “El Niño” became something of a mantra across the parched lands.
There was no pictures.