Hurricane Dora was one of few

tropical cyclones A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...

to track across all three north Pacific basins and the first since Hurricane John in 1994. The fourth named storm, third hurricane, and second major hurricane of the 1999 Pacific hurricane season, Dora developed on August 6 from a

tropical wave A tropical wave (also called easterly wave, tropical easterly wave, and African easterly wave), in and around the Atlantic Ocean, is a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which ...

to the south of Mexico. Forming as a tropical depression, the system gradually strengthened and was upgraded to Tropical Storm Dora later that day. Thereafter Dora began heading in a steadily westward direction, before becoming a hurricane on August 8. Amid warm

sea surface temperatures Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air masse ...

and low

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal ...

, the storm continued to intensify, eventually peaking as a 140 mph (220 km/h) Category 4 hurricane on August 12. Thereafter, Dora fluctuated significantly in intensity due to changes in water temperatures and wind shear, with the storm ranging from peak intensity as a Category 4 hurricane to a low-end Category 1 hurricane over a period of four days. While passing well south of the island of Hawaii on August 16, Dora briefly regained major hurricane status. On August 18, the cyclone passed just south of

Johnston Atoll Johnston Atoll is an Unincorporated territories of the United States, unincorporated territory of the United States, currently administered by the United States Fish and Wildlife Service (USFWS). Johnston Atoll is a National Wildlife Refuge and ...

as a Category 1 hurricane. Although it never made landfall, Dora produced high surf, gale-force winds, and light rain across the islands of Hawaii and Johnston Atoll, but resulted in minimal damage. While crossing the

International Dateline The International Date Line (IDL) is an internationally accepted demarcation on the surface of Earth, running between the South and North Poles and serving as the boundary between one calendar day and the next. It passes through the Pacific O ...

on August 20, Dora weakened to a tropical storm. After weakening to a tropical depression on August 22, Dora dissipated on August 23 while centered several hundred miles north of

Wake Island Wake Island ( mh, Ānen Kio, translation=island of the kio flower; also known as Wake Atoll) is a coral atoll in the western Pacific Ocean in the northeastern area of the Micronesia subregion, east of Guam, west of Honolulu, southeast of To ...

Meteorological history

A tropical wave emerged into the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

from the west coast of

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

on July 23. It tracked through the Atlantic and

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

for several days with minimal development. By August 4, the system entered the Pacific Ocean, accompanied by disorganized

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

. During the next 24 hours, satellite imagery noted evidence of a low-level circulation, as well as the formation of curved convective banding. As a result, it is estimated that Tropical Depression Seven-E developed at 00:00 UTC on August 6, while located about 335 miles (540 km) south of

Acapulco Acapulco de Juárez (), commonly called Acapulco ( , also , nah, Acapolco), is a city and major seaport in the state of Guerrero on the Pacific Coast of Mexico, south of Mexico City. Acapulco is located on a deep, semicircular bay and has bee ...

. Despite initial vertical

, the depression steadily intensified and was upgraded to Tropical Storm Dora later that day. Upon becoming a tropical storm, the storm had decent outflow on its western quadrants. Tracking west-northwestward and then westward along a decaying

subtropical ridge The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as Subtropics, subtropical ridges, or highs. It is a h ...

, Dora continued to intensify and was upgraded to a hurricane on August 8 based on the Dvorak technique. Late on August 8, the storm consisted primarily of

central dense overcast The central dense overcast, or CDO, of a tropical cyclone or strong subtropical cyclone is the large central area of thunderstorms surrounding its circulation center, caused by the formation of its eyewall. It can be round, angular, oval, or irr ...

, but minimal banding features. At 00:00 UTC on August 9, Dora intensified into a Category 2 hurricane. Several hours later, an

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

with a diameter of about 6–12 mi (10–19 km) developed, and the cyclone organized further. The storm strengthened into a Category 3 hurricane around 00:00 UTC on August 10. The hurricane continued westward or slightly north of due west. Late on August 10, deep convection significantly expanded and became more symmetric, while Dvorak intensity estimates indicated that Dora reached Category 4 intensity; the NHC upgraded the storm to a Category 4 hurricane accordingly. Hurricane Dora August 10 1999 1730 UTC

Later on August 11, the NHC predicted relatively slow weakening beginning in about 24 hours, as the storm would cross over slightly colder sea surface temperatures in the wake of

Hurricane Eugene Hurricane Eugene may refer to: * Tropical Storm Eugene (1981) – a weak storm that did not affect land * Hurricane Eugene (1987) – Category 2 storm that made landfall south of Manzanillo, Mexico Manzanillo () is a city and seat of Manzanillo ...

. However, at 00:00 UTC on August 12, Dora attained its peak intensity with maximum sustained winds of 140 mph (220 km/h) and a minimum barometric pressure of . At the time of peak intensity, the hurricane featured a diameter eye, surrounded by cloud tops with temperatures of . Six hours later, Dora weakened slightly due to an

eyewall replacement cycle In meteorology, eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones, generally with winds greater than , or major hurricanes ( Category 3 or above). When tropical cyclones reach this int ...

, but re-attained peak intensity by 12:00 UTC. The cyclone again fell below peak intensity at 12:00 UTC on August 13 due to cooler waters and increasing wind shear. Dora weakened to a Category 3 about six hours later, as the eye became cloud-filled and surrounding cloud tops warmed. Early on August 14, the duty of hurricane advisories was transferred from the NHC to the

Central Pacific Hurricane Center The Central Pacific Hurricane Center (CPHC) of the United States National Weather Service is the official body responsible for tracking and issuing tropical cyclone warnings, watches, advisories, discussions, and statements for the Central Pacifi ...

(CPHC), as the storm had crossed 140°W. By then, the system was weakening significantly and fell to Category 2 intensity around 06:00 UTC. The cyclone had maintained major hurricane status from 00:00 UTC on August 10 to 06:00 UTC on August 14 – more than 96 hours. Dora further deteriorated to a weak Category 1 hurricane by 12:00 UTC on August 14 and was forecast to fall to tropical storm intensity within 24 hours. However,

dropsonde A dropsonde is an expendable weather reconnaissance device created by the National Center for Atmospheric Research (NCAR), designed to be dropped from an aircraft at altitude over water to measure (and therefore track) storm conditions as the devi ...

readings of winds and satellite estimates indicated that Dora re-strengthened to a Category 2 hurricane with winds of 105 mph (165 km/h) around 06:00 UTC on August 15. Shortly thereafter, a well-defined eye again appeared on satellite imagery. The combination of reconnaissance data and satellite imagery supported an upgrade of the storm back to Category 3 intensity at 06:00 UTC on August 16. At the time, Dora was passing about 200 mi (320 km) south of Hawaii – the storm's closest approach to the state. The secondary peak intensity was brief, as weakening occurred shortly thereafter. Dora passed about 65 mi (105 km) south of

on August 18 as a Category 1 hurricane before turning west-northwestward. Around 00:00 UTC on the following day, Dora weakened to a tropical storm as it crossed the

International Date Line The International Date Line (IDL) is an internationally accepted demarcation on the surface of Earth, running between the South and North Poles and serving as the boundary between one calendar day and the next. It passes through the Pacific O ...

. The

Joint Typhoon Warning Center The Joint typhoon Warning Center (JTWC) is a joint United States Navy – United States Air Force command in Pearl Harbor, Hawaii. The JTWC is responsible for the issuing of tropical cyclone warnings in the North-West Pacific Ocean, South P ...

tracked the remainder of the duration of Dora. The storm encountered stronger wind shear, and by August 21, winds decreased below tropical storm force. On August 23, the circulation became exposed from the main convection, and at 18:00 UTC, Tropical Depression Dora dissipated about 450 mi (725 km) northeast of

Impact and records

On August 16, forecast models predicted Dora would bypass

a short distance to the south, with some concerns of a direct hit on the island. As a result of the threat, about 1,200 workers and residents evacuated Johnston Atoll to Hawaii. Prior to leaving, workers secured construction equipment and other loose items. Some

biologist A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual Cell (biology), cell, a multicellular organism, or a Community (ecology), community of Biological inter ...

s on Johnston Atoll were concerned that the hurricane would severely impact the reproductive cycle of over 150,000 birds in the Johnston Atoll National Wildlife Refuge, a concern expressed after Hurricane John in 1994 killed 80% of the island's bird population. Additionally, the Central Pacific Hurricane Center predicted Dora would strike

as a minimal typhoon, though this did not occur. An ocean swell from Dora produced 8–20 ft (2–6 m) waves along the east and southern shores of the island of

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

. This prompted local officials to close all beaches, campsites, and

nature trail An educational trail (or sometimes educational path), nature trail or nature walk is a specially developed hiking trail or footpath that runs through the countryside, along which there are marked stations or stops next to points of natural, techno ...

s in the Puna and Kau districts due to the deteriorating conditions. The outer bands of Dora produced winds of up to 60 mph (95 km/h) at some high elevations. Light rains fell, especially in the northern and eastern portions of the island, with amounts ranging from . However, no precipitation fell in the drought-stricken portions of the island. Hurricane Dora also produced rough surf on Johnston Atoll. The automatic station at Johnston Atoll reported wind gusts between 40–45 mph (65–75 km/h) for two hours. Overall effects were minimal, and there were no reports of damage or injuries. With a total track of about 6,500 mi (10,500 km), Hurricane Dora had the second longest track of a

Pacific hurricane A Pacific hurricane is a mature tropical cyclone that develops within the northeastern and central Pacific Ocean to the east of 180°W, north of the equator. For tropical cyclone warning purposes, the northern Pacific is divided into three regio ...

, behind only Hurricane John of 1994; the length of the track of Dora was more than four times the basin average. Dora was also the first Pacific hurricane to come close enough to be detected by

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

. In addition, the hurricane was the first tropical cyclone to move across all three Pacific basins since John in 1994.

Notes

References

External links

Hurricane Dora Tropical Cyclone Report
of Severe Tropical Storm Dora (9911) from Digital Typhoon
JMA Best Track Data (Graphics)
of Severe Tropical Storm Dora (9911)

{{DEFAULTSORT:Dora (1999) 1999 Pacific hurricane season Category 4 Pacific hurricanes 1999 Pacific typhoon season Hurricanes in Hawaii Western Pacific severe tropical storms 1999 in Hawaii

Meteorological history

Impact and records

See also

Notes

References

External links