Satellites are now the primary tool used by meteorologists to track and forecast hurricane behavior. The GOES geostationary satellites are particularly adept at monitoring multiple storms visible simultaneously in a global hemisphere. Here is a September 3, 2008 GOES image acquired at 1:45 PM EDT that shows five tropical cyclones. Gustav and Ike both slammed into Gulf Coast states, causing billions of dollars in damage:
We look next at several special-interest stories dealing with hurricanes and violent storms that occurred either in the U.S. and/or the Caribbean and Central America. An excellent review of major hurricanes in these regions is found at this NOAA site. Also, you may wish to review the discussion of hurricanes near the bottom of page 14-1d. As a more general examination of cyclone/hurricane development, consider this online Web site: Earth Observatory Hurricanes.
In late August of 1992, Andrew, a category 5 hurricane, ripped through the Bahamas, slammed into southern Florida (its eye or center passed over Homestead Air Force Base), and moved into the Gulf of Mexico to hit Louisiana. Here is a montage of Andrew on different dates as seen with a metsat imager:
Although rather small in diameter, this intense storm was, up to that time, the most costly in U.S. history - estimates as high as $25 billion in damage - even though it took just 43 lives (a tribute to the early warning efficacy of Metsat monitoring). Winds in excess of 240 km/hr (149 mph) flattened entire housing developments. Hardest hit were homes in communities about 25 miles south of downtown Miami:
This devastating hurricane got a lot of attention by a variety of sensors from above and on the ground. Consider these images:
The top image from NOAA-7 shows the hurricane as it strikes land in Florida, with colorized tones representing higher intensities. In the middle is a GOES-7 full-Earth color view obtained on August 25, 1992, in which Andrew is seen approaching New Orleans. This perspective indicates scale, showing the hurricane, while powerful as organized, was still just another mass of clouds of no greater extent than some other storm systems. But, on close-up (bottom) in the AVHRR color version (RGB = 0.9; 1.5R; 3.5 Ám), the perfection of the eye and the well-developed structure of this counterclockwise-spinning, low-pressure system are obvious.
14-25: What do you think happened to Andrew after it made its second landfall around the Mississippi Delta? ANSWER
The Terra and Aqua programs are the subject of Section 16. These two satellites are not designed specifically as Metsats but they do gather considerable data pertinent to weather and climate. Here is a Terra MODIS image of 4 simultaneous hurricanes (called typhoons or cyclones in the eastern hemisphere) crossing the western Indian Ocean on February 12, 2003:
The most destructive cyclone in modern times was Cyclone Nargis, which passed over Myanmar (Burma) on May 2 and 3, 2008. Estimates of those killed range up to 128000. Large parts of villages and towns in the Irrawady Delta were obliterated by winds (the cyclone produced winds up to 160 mph, making it a category 4 storm) or washed away by storm surges up to 10 meters (33 ft) high at the coast. Here is a metsat image of Nargis, and a rainfall map of southern Asia for a week ending May 3:
MODIS has produced these images of the floods in Myanmar; a preflood image is shown for comparison.
The capital of Myanmar, Yangon (used to be known as Rangoon) received extensive flooding:
Entire villages were obliterated, as exemplified here:
The Nargis disaster is a prime example of how satellite imagery can monitor a catastrophic event in near real time.
MODIS has proved a valuable adjunct to hurricane monitoring since its field of view can encompass an entire storm. In September of 2003, Hurricane Isabel reached a category 5 status (winds in excess of 146 mph) as it approached the U.S. Here's how it looked on September 9:
The hurricane season of 2004 was one of the most active and destructive in recent decades. First, in August, Hurricane Charley (Category 4) swept up to the west coast of Florida, going inland below Tampa and crossing the state:
Then, in early September, Hurricane Frances damaged Caribbean islands and the Bahamas before touching land near Fort Pierce on Florida's east coast, crossed the state, and then swung north into the Appalachians. Though its initial winds made it another Category 4 hurricane, these subsided as it struck the U.S. Most damage was done by extensive flooding. Here is a NOAA satellite view of Frances after its march across the Atlantic:
Shortly thereafter, Hurricane Ivan began its assault as a Category 5 hurricane by striking and devastating the island nation of Grenada (85% of the homes there were destroyed or damaged). Then after glancing blows against Jamaica and western Cuba, it has moved against the Gulf Coast east of New Orleans, causing extensive damage in Mississippi, Alabama, and around Pensacola, Florida.:
Tornadoes and swirling squalls with high winds did a great deal of damage in waterfront marinas and homes near Pensacola, shown here in two IKONOS "before (right) and after (left)" scenes:
Then, on September 26 a fourth hurricane, Jeanne, a Category 3 with 115 mph, struck Florida near Fort Pierce and Vero Beach, making almost exactly the same landfall as Frances.
The TRMM provided a measure of the amount of rainfall actually falling, as contoured in this image:
Especially susceptible to hurricane damage are trailer homes anchored on a cement base. Such homes are usually the most readily damaged by the high winds and flooding, as seen here in this Fort Pierce trailer park:
Never before have four major hurricanes struck Florida in one season. The combined dollar estimate for these events is likely to exceed 35 billion. The combined death toll exceeds 100. But before reaching the U.S. Jeanne caused similar devastation, even as it was then only a Tropical Storm, in the Caribbean. At least 1500 people drowned in and near the city of Gonaives in northern Haiti, as homes there were beset by flooding (landslides also contributed to the death toll).
One of the greatest values of meteorological satellites lies in both their realtime tracking capabilities and in their acquisition of data helpful in forecasting their future paths. Here is the prediction of Ivan's course as of 5 AM September 14. In fact, the early morning of September 16 Ivan's Eye struck at Mobile Bay.
Look at Ivan (the Terrible) as it is about to enter the gap between western Cuba and the Mexican Yucatan and into the Gulf of Mexico where it remained a Category 4 hurricane until it came ashore in Alabama, moved up the Appalachians (drenching my house in Pennsylvania with 7 inches of rain), went to New England and - most unusual - turned around, went south over the ocean to Florida, crossed it and finally blew itself out in Texas.:
Astronauts on the International Space Station used their digital camera to photograph in detail the Eye of Ivan:
Research satellites such as Terra and Aqua are adding significant knowledge to understanding hurricane characteristics and mechanisms of development. This Terra MISR image (see Section 16-10) shows how measurements from space can be converted to, in this case, cloud heights in different parts of Hurricanes Frances and Ivan.
One goal in using satellites to monitor hurricanes is to use space observations and measurements to improve estimates of intensity (Category levels). This can be done when profiles of wind speeds are obtained. This is possible from Cloudsat data, as illustrated here for Hurricane Ileana in 2006 (the top image is from Aqua):
Cloudsat obtains its radar images by bounding radar waves off of fine-sized ice particles in the rain sheets. This type of image appears at the bottom of this view of Hurricane Jimena off Baja California in late August; a MODIS image of that hurricane is shown above:
This next MODIS image is a rarety, maybe even a first. Here is an ISS astronaut photo of an unnamed hurricane in the South Atlantic moving off the coast of Brazil in late March 2004. Conditions are very unfavorable for hurricane development below the equator in that ocean. Records indicate that this may be the first such hurricane ever to form in the South Atlantic, which accounts for why no name was given it (no list has ever been needed).
Another sensor on TRMM, which can get vertical profile data, has added to our knowledge of hurricane structure. Convective clouds, called "hot towers" can rise from the main cloud deck of a hurricane, approaching the top of the troposphere, releasing latent heat enroute. This leads to cooling and condensation to produce columns of rainfall. In the 1998 Hurricane Bonnie, the towers reached to an altitude of 18 km (11 miles) as shown in this illustration:
A recently determined phenomenon in hurricanes is a drop in total ozone above the heavy wind/rain segments of a hurricane. An Earth Probe TOMS produced this ozone map for Hurricane Erin:
Satellites that measure ocean water temperatures give forewarnings of thermal conditions in tropical waters that control and breed hurricanes and tropical storms. This image, made by the AMSR instrument on Aqua, shows the heating of Atlantic equatorial waters in the early summer of 2003:
Since this page was prepared (with the assumption that after Hurricanes Andrew and Ivan were about the worst to hit the U.S.), a monster hurricane, Katrina struck first Florida and then the Gulf states with a devastating below. So much information needs documentation here that a separate page is warranted. Access it by clicking on page 10a.
Leaving hurricanes - perhaps nature's most spectacular storms - we turn to land-based storms that can be quite destructive. On March 13, 1993, the "Storm of the Century", shown here in this GOES-7 image, with more intense clouds (color-enhanced), struck the eastern U.S. with massive snow falls and high winds.
One class of snowstorms (or if too warm, extensive rainfalls) is the so-called "noreaster". The term has two meanings: first, this storm is especially common in the northeastern U.S.; second, the winds tend to be coming from the northeast, i.e., blow towards the southwest. This is illustrated by this schematic for a noreaster over Massachusetts:
Some noreasters are huge. The storm of February 8, 2010 covered most of the eastern U.S. into the Carolinas. It dumped more than 20 inches of snow on Washington, Baltimore, and Philadelphia. Here are two satellite images:
Snowfalls are usually widespread. But under some conditions a blanket of snow covers only a rather limited region. This happened on February 26-27, 2004 when a foot or more of snow was dumped by a clipper storm passing over much of North Carolina. This is how it looked the day after, as seen from MODIS. With such imagery one can delineate snow accumulation boundaries with high accuracy:
Metsats are excellent monitors of less violent, more conventional, but still interesting weather data. We are all familiar with the passage of cold fronts, followed by clear weather as a pressure high moves in. Commonly, moist, warm air is encountered by the front and develops into a broad area of clouds and often stormy weather. This next image shows the sharp leading edge of a front now off the Atlantic coast of the U.S. and out to sea. At its back edge is another sharp boundary beyond which cold, dry air is moving in.
Tornadoes, while much more localized than hurricanes or subcontinental storms, can do incredible damage to the areas on which they touch down. Viewed at close distances, most tornadoes have an ominous, sometimes terrifying look, that helps to explain why they are so feared (add to this the knowledge of the horrendous damage they can cause). Here is an example:
Tornadoes are low pressure systems, and can generate wind velocities that can exceed 200 mph. Severe ones will flatten buildings (tornadoes have a special fondness for trailer parks), uproot trees, and carry objects for hundreds of feet to even miles from their spot of origin. The storms that brew them are effectively tracked by ground radar and by satellites (usually geostationary). On May 27, 1997 several lines of storm clouds bearing multiple funnel clouds crossed central Texas with deadly results. Here is a GOES-8 image of these advancing fronts.
When a storm has passed and the sky clears, a passing satellite can often see the actual damage if conditions are right. This was the case three days after a killer tornado touched down on May 5, 1999 within Oklahoma City, OK., cutting a path through city and suburbs and just missing the airport. Look for the diagonal blue strip in this IRS-C LISS false color composite - this marks the zone of heavy destruction.
Now that IKONOS and other high resolution sensors are operational, it is feasible to inspect damage from tornadoes in considerable detail - equivalent to flying an aerial photo mission. A tornado touched down in Fort Worth, TX, ripping off roofs from warehouses and other buildings, as evident in this 1 m resolution IKONOS image.
The first tornadic storm of 2002 to produce multiple deaths (4) occurred on April 28 around La Plata, Maryland, about 40 miles southeast of Washington. This may have been an F-4 tornado (the second highest wind category) and as such was the most powerful ever to hit Maryland (and one of the strongest ever to hit the East Coast region). Within just two days, the narrow path of destruction (that was, however, 6 miles long) in which several hundred buildings were damaged was imaged by EO-1, as seen here (the pink color was caused by destruction of vegetation [reducing the natural green input]):
Still another hazard, and sometimes a killer, associated with usually severe storms are lightning strikes. Worldwide thousands of individual lightning discharges, including dramatic bolts, occur each day.This next map shows the geographic distribution of the frequency of strikes averaged over 5 years (1995-2000) of data collecting by NASA's Optical Transient Detector and by the Lightning Imaging Sensor on TRMM. Note that the central part of Africa has the most lightning strikes; almost all of South America is prone to frequent electrical storm activity.
A different perspective occurs when one looks at the distribution of lightning strikes on a monthly basis, as plotted in this global map.
Still, when compared with the previous global map, similarities are evident.
A less well known phenomenon is the occurrence of "sprites", a term applied to electrical discharges in the upper atmosphere (ionosphere) at altitudes from 60 to 100 km. These develop almost coincidence with ground strikes. The Republic of China's ROCSAT has an instrument (ISUAL - Imager of Sprites and Upper Atmosphere Lightning) that concentrates on studies of this type of discharge (dissociation of rarified gases accompanying the lower atmosphere lightning strikes). Here is an ISUAL image of the near surface lightning and above it a reddish glow from ionized nitrogen