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This part of Section 14, which deals with meteorological satellites and the value of observing the Earth’s weather system from space, closes with two major episodes in the 1990s that made weather history. The first was Hurricane Andrew in 1992 which struck land below Miami; before it dissipated to the north, it caused $30 billion dollars in damages - the costliest natural disaster in American history. The second was the infamous "Storm of the Century" in March 1993 which buried the northeast U.S. under a massive snowfall. Satellite images give some idea of the intensity of both these events. Hurricanes are by far the most costly (in terms of scope of damage) of storms. Tornadoes, also very destructive, can sometimes be captured (actually, the unstable air mass that spawns them) in satellite imagery and damage assessment made through space imagery after the storm has passed. Lightning strikes, another storm hazard, happen with high daily occurrences and are most frequent in central Africa and South America, as determined from data obtained by sensors dedicated to their detection.


Hurricane Andrew; Hurricanes & Tornadoes; 1993 Storm of the Century; Lightning Discharges

We close this part of Section 14 with 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.

In late August of 1992, Andrew, a category-five 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. Although rather small in diameter, this intense storm was 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:

A housing development near Homestead Air Force Base, in which most homes were totally destroyed by Hurricane Andres.

This devastating hurricane got a lot of attention by a variety of sensors from above and on the ground. Consider these images:

Colorized NOAA-7 image of Hurrican Andrew as it strikes land in Florida.

GOES-7 color composite showing North and South America and the eastern Pacific; a large roundish white cloud in the north-central part of the Gulf of Mexico is Hurricane Andrew approaching landfall near New Orleans.

Color AVHHR closeup view of Andrew over New Orleans.

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 approaches 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 µm), 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 hurricanes (typhoons in the eastern hemisphere) crossing the western Indian Ocean on February 12, 2003:

MODIS image of Indian Ocean typhoons; from left to right - Gerry, Hope, 18s (poorly organized), Fiona.

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:

Hurricane Isabel, Sept. 9, 2003; MODIS image.

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:

Hurricane Charley, with its swirls colorized to show varying wind speeds, as it is here position over the center of Florida.

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. Those its initial winds made it another Category 4 hurricane, these subsided as it struck the U.S. but most damage was done by extensive flooding. Here is a NOAA satellite view of Frances' after its march across the Atlantic:

Hurricane Frances.

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.:

Ivan as it passes through the Caribbean

Tornadoes and swirling squalls with high winds did a great deal of damage in waterfront marinas and homes near Pensacola, shown here in two ILONOS "before and after" scenes:

Pre- (right) and Post- (left) Ivan views of a village near Pensacola.

Then, on September 26 a fourth hurricane, Jeanne, a Category 3 with 115 mph, struck Florida near Fort Pierce and Vero Beach, almost exactly the same landfall as Frances.

Hurricane Jeanne.

The TRMM provided a measure of the amount of rainfall actually falling, as contoured in this image:

TRMM rainfall measurements during Jeanne's passage (eye on eastern coast).

As with Frances, the writer (NMS) has a personal tie to Jeanne. His wife's retired brother lived in Fort Pierce. His substantial home apparently survived reasonably well during the storm. But other neighbor's in this retirement community faired badly, especially if they lived in 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:

Destroyed trailer homes at Fort Pierce, FL.

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).

IKONOS image showing Gonaives submerged by rain water flooding from then Tropical Storm Jeanne.

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.

The path of Ivan, as a forecast.

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.:

NOAA satellite image of Ivan on September 13, 2004.

Astronauts on the International Space Station used their digital camera to photograph in detail the Eye of Ivan:

Ivan's central swirls, with a clearly defined eye.

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.

MISR determinations of cloud heights in Hurricanes Frances and Ivan.

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).

The 2004 South Atlantic hurricane, photographed by an astronaut on ISS on March 28.

14-25a: How does this hurricane differ from the ones shown above (hint: think southern hemisphere behavior of the Coriolis force)? ANSWER

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:

Hot towers associated with Hurricane  Bonnie.

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:

Ozone depletion around the eye of Hurricane Erin, as measured by TOMS.

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:

Warm zones in Atlantic equatorial waters monitored by Aqua in Summer 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.

Colorized GOES-7 image of the "Storm of the Century," March 13 1993.

The writer (NMS) at the time was in Bloomsburg, Pennsylvania, preparing to leave the next day to give a paper on the Manson Impact Structure (see page 18-2) at the Lunar and Planetary Science Conference in Houston, TX, the first he was to attend since the original Conference on Apollo 11 moon rocks 23 years earlier. It was not to be. Snow locally exceeded 60 cm (24 in), driven into deep banks by winds. All Interstate highways within Pennsylvania closed for two days.

Snowfalls are usually widespread. But under some conditions a blanket of snow covers only a rather limited region. This happend 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:

Extent of snowfall in North Carolina in late February 2004 as seen by the MODIS sensor or Terra.

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.

Passage of a cold front across the Eastern U.S. and onto the Atlantic Ocean.

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:

An approaching tornado.

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.

GOES-8 image of the storm front containing a line of killer tornadoes in a weather front crossing Texas on May 27, 1997.

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.

Tornado path (blue diagonal) in Oklahoma City, imaged by the IRS-C LISS.

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.

Damaged buildings in the warehouse district of Fort Worth, TX, following a tornado in 2000; imaged by IKONOS.

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]):

EO-1 image of the path of an F-4 tornado that here crosses homes around La Plata, MD.

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.

Global map of frequency of lightning strikes; the areas of greatest number of strikes from 1995 to 2000 are shown in blacks, then reds; lowest blues.

A different perspective occurs when one looks at the distribution of lightning strikes on a monthly basis, as plotted in this global map.

Lightning flashes per month.

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

Sprite discharge occurring almost simultaneously with a ground lightning discharge.

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Primary Author: Nicholas M. Short, Sr. email: nmshort@ptd.net