Glow of lava is reflected in steam plume at water’s edge east of Kupapa‘u Point. A littoral cone formed by spatter from steam explosions sits on top of the sea cliff to the right (photo by T.J. Takahashi

Cumulonimbus Cloud over Africa. Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center. ISS016-E-27426

Cumulonimbus Cloud over Africa
Perhaps the most impressive of cloud formations, cumulonimbus (from the Latin for “pile” and “rain cloud”) clouds form due to vigorous convection (rising and overturning) of warm, moist, and unstable air. Surface air is warmed by the Sun-heated ground surface and rises; if sufficient atmospheric moisture is present, water droplets will condense as the air mass encounters cooler air at higher altitudes. The air mass itself also expands and cools as it rises due to decreasing atmospheric pressure, a process known as adiabatic cooling. This type of convection is common in tropical latitudes year-round and during the summer season at higher latitudes.

Hurricane Isabel. Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center. ISS007-E-14887

Astronaut Ed Lu snapped this oblique photo of Hurricane Isabel from the International Space Station on September 15, 2003 at 10:54 UTC. At the time, Isabel was heading for the east coast of the US . It had dropped to a Category 3 hurricane on the Saffir-Simpson Hurricane Scale. After originating in the eastern Atlantic west of the Cape Verde Islands, Isabel became the second major hurricane of the 2003 Atlantic season when it was declared a Category 3 storm by the National Hurricane Center on September 8. Over the next four days, Isabel strengthened into an extremely powerful Category 5 hurricane with winds estimated at 160 mph before dropping in strength as it approached the US.

Large thunderstorm. Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center. STS097-351-9

These two images were taken 9 seconds apart as the STS-97 Space Shuttle flew over equatorial Africa east of Lake Volta on December 11, 2000. The top of the large thunderstorm, roughly 20 km across, is illuminated by a full moon and frequent bursts of lightning. Because the Space Shuttle travels at about 7 km/sec, the astronaut perspectives on this storm system becomes more oblique over the 9-second interval between photographs. The images were taken with a Nikon 35 mm camera equipped with a 400 mm lens and high-speed (800 ISO) color negative film.

Overshooting thunderstorm. Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center. STS073-E-5151

night-time thunderstorm. Credit: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)

Time-lapse photography captures multiple cloud-to-ground lightning strokes during a night-time thunderstorm in Norman, Oklahoma in March, 1978.

Globular mammatus clouds. Credit: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)

Globular mammatus clouds with radar in foreground. Often associated with thunderstorms and severe weather.

Supercell - often associated with violent weather. Credit: NOAA Photo Library, NOAA Central Library; OAR/ERL/National Severe Storms Laboratory (NSSL)

NASA image by Jeff Schmaltz, MODIS Rapid Response, NASA Goddard Space Flight Center.

After 10 months of relative quiet, Soufriere Hills volcano on the Caribbean island of Montserrat blasted ash into the sky in early October 2009. This natural-color satellite image shows a plume of ash extending westward from Soufriere Hills on October 6, 2009, a day after eruptive activity resumed on October 5th. According to the U.S. Air Force Weather Agency, ash extended 280 kilometers (170 miles) at an elevation of approximately 3,600 meters (12,000 feet).

Soufriere Hills is a stratovolcano composed of alternating layers of hardened lava, solidified ash, and rocks ejected by previous eruptions. After the seventeenth century, the volcano experienced no recorded eruptions until 1995, when a series of major eruptions eventually forced the evacuation of the Montserrat’s former capital city, Plymouth.

APIA, SAMOA – OCTOBER 03: An aerial view of the devastaion along the South East coastline of Samoa is seen following the 8.3 magnitude strong earthquake which struck 200km from Samoa’s capital Apia on Tuesday, on October 3, 2009 in Apia, Samoa. The quake triggered a tsunami wave up to 1.5 metres across areas of the island, with the official death toll in Samoa standing at 149. A further quake measuring 6.3 struck 85 kilometres south-east of Tonga, but no tsunami warning or additional casualties have been reported as yet. (Photo by Phil Walter/Getty Images)

LALOMANU, SAMOA – SEPTEMBER 30: A man survey the debris at the beach following yesterday’s 8.3 on the Richter scale strong earthquake which struck 200km from Samoa’s capital Apia at 6.48am local time on September 30, 2009 in Lalomanu, Samoa. The quake triggered a tsunami wave up to 1.5 metres across areas of the island, with a death toll currently sitting at 113 fatalities but expected to rise. (Photo by Phil Walter/Getty Images)

The topography of Tutuila, largest of the islands of American Samoa, is well shown in this color-coded perspective view generated with digital elevation data from the Shuttle Radar Topography Mission (SRTM.) On September 29, 2009, a tsunami generated by a major undersea earthquake located about 200 kilometers (120 miles) southwest of Tutuila inundated the more heavily populated southern coast of the island with an ocean surge more than 3 meters (10 feet) deep, causing scores of casualties. Image by NASA/JPL/NGA

The topography of Savai’i (background) and Upolu (foreground), the two large islands of the Independent State of Samoa, is well shown in this color-coded perspective view generated with digital elevation data from the Shuttle Radar Topography Mission (SRTM.) On September 29, 2009, a tsunami generated by a major undersea earthquake located about 200 kilometers (120 miles) south of Samoa inundated villages on the southern coast of the islands with an ocean surge perhaps more than 3 meters (10 feet) deep. It also impacted the more heavily populated northern coasts with a surge measured at nearly 1.5 meters (4 feet) at the capital city Apia (on Upolu). Image by NASA/JPL/NGA

An overflowing sewer on Riverside Road, Roswell, Georgia. Photo by Alan Cressler, USGS

The flooding around Atlanta this week is one for the record books. According to the U.S. Geological Survey (USGS), the rivers and streams had magnitudes so great that the odds of it happening were less than 0.2 percent in any given year. In other words, there was less than a 1 in 500 chance that parts of Cobb and Douglas counties were going to be hit with such an event.

“The USGS can reliably say just how bad these floods were. They were epic!” said Brian McCallum, Assistant Director for the USGS Water Science Center in Georgia. “We have all witnessed the devastation caused by these floods, but now we can quantify it.” The data are gathered from the USGS real-time streamgaging network.

The discharge at this site on the Chattahoochee was around 60,400 CFS (cubic feet per second) on Sept. 22, 2009. The river was measured and sampled during the peak discharge that occurred during flooding.

USGS hydrographers using a D-96 weighted sampler. It weighs 132 pounds without the force of water. You can see the heavy steel counterweights on the four-wheel base to keep it from toppling into the water. Hydrographers have to be especially carefully in floods because floating trees can catch the sampler and then everything goes in. Credit: U.S. Geological Survey

Interstate 20 was closed west of Atlanta for around two days because of Sweetwater Creek flowing over it. This U.S. Geological Survey crew is completing a discharge measurement in the west bound lanes of the Interstate. They measured 5,000 cubic feet per second (CFS) crossing the interstate. The crew measuring the discharge at the actual bridge measured around 25,000 CFS. Photo by Alan Cressler, USGS.

NIAS, INDONESIA – MARCH 31: Boys make their way around the eartquake cracked streets during rescue operations March 31, 2005 in Gnung Sitoli, Nias, Indonesia. An earhquake measured 8.7 on the Richter scale hit the South East Asian region of Sumatra at 11:09 pm local time on March 28 and reportedly lasted 2 minutes. The island of Nias off the coast of Sumatra was the hardest hit with the death toll estimated at two thousand people. (Photo by Daniel Berehulak/Getty Images)

PENGALENGAN, WEST JAVA, INDONESIA – SEPTEMBER 04: A road lies collapsed following the September 2nd earthquake, on September 4, 2009 in Pangalengan, Indonesia. The 7.0-magnitude earthquake has caused widespread damage across West Java province damaging more than 18,000 homes, leaving more than 5000 people seeking refuge in makeshift tents.. The deathtoll currently stands at 57 with more than 100 people in hospital and dozens still missing. (Photo by Ulet Ifansasti/Getty Images)

PADANG, INDONESIA – OCTOBER 02: An Indonesian rescue worker walks through the rubble of the Ambacang Hotel on October 2, 2009 in Padang, Indonesia. An earthquake of magnitude 7.6 struck at 5.16pm local time 85km under the sea north-west of Padang on September 30. According to reports officials have reported a death toll of 700 in the port city of Padang. However, that is expected to rise to over 1,000. (Photo by Daniel Berehulak/Getty Images)

PADANG, INDONESIA – OCTOBER 1: A mosque collapses in the wake of an earthquake October 01, 2009 in Padang, West Sumatera, Indonesia. According to reports the official death toll stands at over 400, however, thousands are feared dead on the island after an earthquake struck the area yesterday. A second quake happened some 12 hours later, 150 miles from Padang. (Photo by Yuli Seperi/Getty Images)