Technical Report 99-01
1998 Atlantic Tropical Storms Views from the NOAA Satellites
by the
NCDC Research Customer Service Group
March 1999
This annual report is a preliminary summary of the 1998 Atlantic Hurricane season which provides a synopsis of each named tropical storm using textual information obtained from the National Hurricane Center#s Summary of the 1998 Atlantic Season report and the National Weather Service#s Preliminary Storm Data reports. Selected satellite and doppler radar imagery were used for key times of each storm. The tables of station precipitation data were created from NWS cooperative and airport stations. The numbers for deaths and damages were obtained from several sources including the NHC Preliminary Hurricane Reports, Federal Emergency Management Agency (FEMA), and state emergency management agencies. These numbers are subject to revision.
The colorized satellite images from the GOES-8 satellite were created using one of the long-wave infrared channels (~10.7um), which measures radiated energy from the earth and atmosphere. The radiance counts were calibrated and converted to brightness temperatures and then scaled to an arbitrary color range, which best displays clouds of various types and heights. The scale ranges from black, indicating the warmest surfaces, to maroon, indicating the coldest surfaces (see fig. 1). Land and ocean surfaces are relatively much warmer than cloud tops, and hence, appear gray to almost black in the series of infrared images within this report. In some cases, color was manually edited to land and ocean areas to further enhance the images. The visible satellite images were created using the Imager visible channel (.52um-.75um) which measures reflected energy in terms of albedo. The visible images are displayed in a gray scale (0-255). The satellite images within this report along with many more tropical storm images are on-line under the satellite resources section at http://www.ncdc.noaa.gov/data-access/satellite-data.
The 1998 hurricane season will be remembered for a number of reasons, but, by far, it will be remembered as the most deadly hurricane season in over 200 years. One of the most powerful hurricanes on record, Hurricane Mitch, is blamed for an estimated 11,000 deaths in Central America. Not since the Hurricane of 1780, which took over 20,000 lives, was there such a deadly storm in the Caribbean Sea region. Other noteworthy tidbits for this season are: Mitch set a record for strongest hurricane in October; the 4-year period, 1995-1998, saw 33 hurricanes, the most hurricanes in any consecutive 4-year group; and for the first time this century, there were four simultaneously occurring hurricanes in the Atlantic, as shown in this GOES colorized infrared image (fig. 2) taken on September 26.
As El Nino was the main contributing factor to last season#s minimal hurricane activity, this year#s explosive activity was directly related to the rapid reversal of El Nino conditions to La Nina conditions during late spring and early summer. La Nina is a weather phenomenon marked by colder than normal sea surface temperatures along the eastern and central equatorial Pacific and is known to impact the weather patterns around the globe. Soon after when La Nina conditions formed, the Atlantic Basin witnessed the formation of 10 named storms within a period of just 36 days from August 19 through September 23. Favorable (weak) wind shear and above normal sea surface temperatures in portions of the Atlantic Basin contributed to this development. Table 1 gives the name, date range, minimum central pressure, maximum sus-tained wind speed, highest Saffir-Simpson category, estimated number of deaths, and damage estimates of each storm.
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