page_title: Hurricane Danielle (1998)
section_title: Meteorological history
hierarchical_section_title: Hurricane Danielle (1998) / Meteorological history
caption_attribution_description: Hurricane Danielle off the Eastern Seaboard of the United States as a Category 2 hurricane.
context_page_description: Hurricane Danielle resulted in minor damage throughout its duration as a tropical cyclone in late August and early September 1998. The fourth named storm and second hurricane of the annual hurricane season, Danielle originated from a tropical wave that emerged off the western coast of Africa on August 21. Tracking generally west-northwestward, the disturbance was initially disorganized; under favorable atmospheric conditions, shower and thunderstorm activity began to consolidate around a low-pressure center. Following a series of satellite intensity estimates, the system was upgraded to Tropical Depression Four during the pre-dawn hours of August 24, and further to Tropical Storm Danielle that afternoon. Moving around the southern periphery of the Azores High located in the northeastern Atlantic, quick intensification to hurricane status occurred early on August 25. By 0600 UTC the following day, Danielle reached an initial peak intensity of 105 mph, a Category 2 hurricane. Increased wind shear from a nearby trough encroached on further development later that day, and subsequently led to slight weakening.
context_section_description: The origins of Hurricane Danielle trace back to a tropical wave that emerged off the western coast of Africa and into the eastern Atlantic Ocean early on August 21. Tracking west-northwestward, the National Hurricane Center (NHC) began Dvorak satellite intensity estimates later that morning following the consolidation of convection – shower and thunderstorm activity – near the system's center. Favorable atmospheric conditions led to further organization, and it is estimated that the disturbance intensified into a tropical depression by 0600 UTC on August 24, while located roughly 690 miles (1,110 km) west-southwest of the Cape Verde Islands. Operationally, the National Hurricane Center initiated advisories at 1530 UTC and noted that the depression was already on the verge of tropical storm intensity. The depression was upgraded to Tropical Storm Danielle later on August 24 following an increase in organization on satellite imagery. 
  As the cyclone moved northwestward along the southern periphery of the Azores High, it began a period of rapid deepening in which a "pinhole" eye became distinguishable on satellite imagery; on this basis, Danielle was upgraded to a hurricane at 1200 UTC on August 25. At the time, Danielle was a compact system, with tropical storm force winds spanning only 115 miles (185 km) from the center. Although the NHC was fairly certain that the storm would continue west-northwestward, a veer north or south of the forecast track seemed plausible due to the influence of an upper-level low to the west-northwest of Danielle. Nonetheless, the storm continued its west-northwest track. At 0600 UTC on August 26, Danielle attained its maximum sustained wind speed of 105 mph (165 km/h), one of four peak intensities. Although the eye became obscured and southeasterly vertical wind shear increased late on August 26, the National Hurricane Center did not indicate weakening and instead predicted that Danielle would reach winds of 120 mph (195 km/h) by late on August 27. Early on August 27, a United States Air Force reconnaissance aircraft flight reported surface winds of 80 mph (130 km/h), though post-analysis indicates that the intensity of the storm was underestimated. 
  The storm briefly re-strengthened slightly on August 27, reaching its maximum sustained wind speed of 105 mph (165 km/h) for the second time at 1200 UTC. Vertical wind shear persisted and Danielle soon began to weaken again. Later on August 27, the National Hurricane Center predicted that the storm would travel along the periphery of an anticyclone centered just east of Bermuda, which would keep the storm away from the East Coast of the United States. Despite being in an apparently favorable environment, Danielle continued to slowly weaken, as the forecast for decreasing wind shear did not initially materialize. Additionally, upwelling from Hurricane Bonnie roughly a week earlier contributed to a decrease in strength. Although the storm weakened further, reconnaissance aircraft observations on August 29 concluded that the structure of Danielle had improved compared to the previous day. By early on August 30, Danielle had weakened to the extent that it was only a minimal hurricane, with maximum winds of 75 mph (120 km/h) at the time. On August 30, the National Hurricane Center noted that Danielle would soon leave the upwelling track left by Bonnie, and likely lead to intensification. Thus, the possibility of re-strengthening increased, though predictions only showed gradual intensification. 
  By early on August 31, an increase in sustained winds, a decrease in barometric pressure, and a 23 miles (37 km) wide eye observed by reconnaissance aircraft all suggested that Danielle was beginning to intensify. On August 31, the anticyclone near Bermuda caused Danielle to curve northeastward, away from the East Coast of the United States. Later that day, a significant increase in intensity led the storm to again reach its maximum sustained wind speed of 105 mph (165 km/h). On September 1, there was significant uncertainty in the future intensity of Danielle,
caption: Satellite image of Danielle off the U.S. East Coast
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