Figure 1. Best Track analysis of Hurricane Karl. 1
Light Red=Category 1-2 Hurricane
Dark Red=Category 3-5 Hurricane
Karl formed from a tropical wave that pushed off the west coast of Africa between 13 and 14 September. (See Figure 2). A weak surface low developed along the wave axis the next day, but thunderstorm and shower activity remained too spotty to classify the low as a tropical entity.
Over the next 36 hours, convection began to increase around the periphery of the low pressure center, and at 06 UTC on 16 September, the National Hurricane Center classified the low as Tropical Depression Twelve, about 670 miles west-southwest of the Cape Verde Islands.2 Just six hours later, TD 12 had become sufficiently well organized to be categorized as Tropical Storm Kyle, the eleventh named storm of the 2004 Atlantic Hurricane Season.
Initial steering for Kyle was provided by a strong subtropical ridge entrenched north of the cyclone, which allowed it to move a little north of due westward for the first three days. By the evening of 18 September, Karl had strengthened a Category 1 hurricane with 70 kt (80 mph) surface winds. By 20 September, however, a large and powerful trough began to erode the subtropical ridge on the western side, allowing Karl to make a turn to the north (See Figure 3). At the same time, Karl strengthened into a powerful 125 kt (145 mph) Category 4 hurricane about 1025 miles east of the northern Leeward Islands.3
Karl began to weaken shortly thereafter while moving into cooler Atlantic waters and an area of increasing shear. At 00 UTC on 25 September, Karl had lost tropical characteristics in the north Atlantic, but remained a formidable extratropical storm with surface winds near 55 kts (65 mph) as it headed towards Iceland and Norway from 26 to 28 September.
Figure 2. Surface Analysis valid 12Z on September 14, 2004. The Tropical Wave seen just off the African Coast will eventually develop in major hurricane Karl during the following days.4
Figure 3. 500 mb reanalysis valid 12Z September 21, 2004 showing a strong cold core low situated over the Canadian Maritimes, creating a weakness in the subtropical ridge to the southeast. Image courtesy of NCEP/NCAR Reanalysis team
Data, Images and Animations
+Explore and analyze gridded data of the hurricane using the GES-DISC Interactive Online Visualization and Analysis Infrastructure (Giovanni)
+Use Mirador or WHOM to obtain data provided by the GES DISC DAAC for a hurricane event.
+View animations and images of Hurricane Karl in the 2004 Past Hurricane Archive.
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MODIS Terra RGB using the MOD02HKM product. This image is of the swath data from Sept 21 at 1330 hrs. More images like this and parameters animation created from other datasets can be seen in our Archive Image Gallery for hurricane Karl
1. Image courtesy of the NOAA coastal Services Center Http://hurricane.csc.noaa.gov/hurricanes
2. Franklin, James. “Tropical Depression Twelve Advisory Number 1” 16 September 2004. http://www.nhc.noaa.gov/archive/2004/pub/al122004.public.001.shtml? (4 August 2006).
3. Pasch, Richard. “Hurricane Karl Advisory Number 19.” 21 September 2004. http://www.nhc.noaa.gov/archive/2004/pub/al122004.public.019.shtml? (4 August 2006).
4. Image Courtesy of Chris Burr at the NHC