Preliminary Report
Hurricane Karl
23 - 29 September 1998

1998 PRELIMINARY REPORTS

Tropical Storm Alex (TS)
Hurricane Bonnie (3)
Tropical Storm Charley (TS)
Hurricane Danielle (2)
Hurricane Earl (2)
Tropical Storm Frances (TS)
Hurricane Georges (4)
Tropical Storm Hermine (TS)
Hurricane Ivan (1)
Hurricane Jeanne (2)
Hurricane Karl (2)
Hurricane Lisa (1)
Hurricane Mitch (5)
Hurricane Nicole (1)

Hurricane Karl was one of four hurricanes in existence over the Atlantic basin at one time. It remained over water without any direct effects to land.

 

a. Synoptic History

Hurricane Karl developed from a small low of non-tropical origin that was tracked from the coast of the Carolinas beginning on 21 September. Deep convection became better organized as the low moved eastward and the "best track" indicates that a tropical depression formed from the disturbance near 1200 UTC 23 September while centered about 50 nautical miles west-northwest of Bermuda. Convective banding increased and the system became Tropical Storm Karl that evening. The tropical cyclone began moving east-southeastward about this time.

Satellite imagery showed the gradual development of a more symmetrical cloud pattern with the center becoming embedded within the coldest convective tops. Karl became a hurricane near 1200 UTC 25 September while centered about 550 nautical miles east-southeast of Bermuda. At this time, Hurricane Georges was over the Straits of Florida, Hurricane Ivan was over the North Atlantic about 500 nautical miles west-southwest of the Azores, and Hurricane Jeanne was over the tropical Atlantic about midway between Africa and the Lesser Antilles. Thus, Karl became the fourth hurricane to co-exist over the Atlantic. According to records at the NHC, the last time four hurricanes were in existence in the Atlantic at the same time was on August 22, 1893. Records also note that on September 11, 1961, three hurricanes and possibly a fourth existed.

Karl began to move toward the northeast in response to a large mid- to upper-level trough to the west of the hurricane. A well-defined eye developed and it is estimated that Karl first reached a maximum intensity of 104 mph at 0000 UTC 27 September while centered about 875 nautical miles east-northeast of Bermuda. The eye remained distinct for at least six hours, after which time the hurricane started to weaken primarily due to increasing upper-level shear.

The hurricane accelerated toward the northeast and weakened to a tropical storm by 0000 UTC 28 September while centered over 23C water about 175 nautical miles west-northwest of the westernmost Azores. Karl continued moving over increasingly cooler waters and became extratropical later on the 28th as the circulation center became well removed from any deep convection. The extratropical cyclone was tracked to south of Ireland by late on the 29th.

b. Meteorological Statistics

As usual for a tropical cyclone not threatening land, satellites provided the primary source of observational data. Dvorak technique location and intensity estimates from the satellite data were produced by the Air Force Weather Agency (AFGWC in figures), the NOAA Synoptic Analysis Branch (SAB) and the NOAA Tropical Analysis and Forecast Branch (TAFB). The highest official Dvorak T number was 5.0 (104 mph) from TAFB and SAB near 0000 and 0600 UTC 27 and is the basis for estimating the peak intensity near these times.

c. Casualty and Damage Statistics

There were no reports of casualties or damage from Karl received at the NHC.