Thursday, September 29, 2016

Hurricane Matthew (2016)

Storm Active: September 28-October 9

On September 22, a tropical wave exited in the African coast and moved rapidly westward across the Atlantic. For the next few days, the wave remained south of 10°N and embedded in the Intertropical Convergence Zone. Combined with the dry air over the east Atlantic, this factor precluded development initially. By the 26th, thunderstorm activity had increased and spiral bands had begun to appear on the north side of the disturbance. The system was still too far south to acquire spin, but it began to move west-northwest over the following day and acquired additional organization. By September 27, the wave was generating winds to near tropical storm force, but had not yet developed a closed circulation. Early on September 28, the system appeared on satellite imagery to be more organized, and aircraft reconnaissance confirmed the presence of a closed circulation later that day. Therefore, advisories were initiated on Tropical Storm Matthew. The aircraft also estimated that surface winds of 60 mph were already present, making the newly formed Matthew already a strong tropical storm.

At the time of formation, Matthew was passing through the Lesser Antilles and entering the Caribbean, bringing strong storms to the region. During the morning of September 29, moderate shear out of the southwest exposed the center briefly. However, high ocean temperatures and increasing humid air near the system allowed an inner core to quickly develop. By the middle of the afternoon, Matthew had strengthened to a hurricane. Meanwhile, the cyclone veered slightly south of west. Overnight, strengthening continued, bringing Matthew to category 2 status by the morning of September 30. Conditions began to deteriorate in the northernmost areas of Columbia later that morning. It is very unusual for tropical cyclones to affect South America, but Matthew's track was quite far south through the Caribbean. Around the same time, an eye appeared on satellite imagery and further rapid intensification took place. That afternoon, the system vaulted through category 3 and up to category 4 status. During the late evening, Matthew peaked as a category 5 hurricane with winds of 160 mph and a central pressure of 941 mb, making it the first category 5 hurricane in the Atlantic since Felix in 2007. Achieving this intensity at 13.3°N latitude, it was also the southernmost category 5 hurricane ever recorded in the Atlantic.

The forward speed of the system had slowed considerably at this point, although it was still moving west or just south of west. Early on October 1, the eye shrunk and the inner core became less organized, resulting in some weakening that day. This weakening was temporary, however, for after completing a small cyclonic loop that afternoon, Matthew regained strong category 4 strength and its new lowest pressure of 940 mb. The cyclone's motion remained slow and somewhat erratic through the following day, averaging to a general northwestward track during the day of October 2. Later that day, the outer rain bands of Matthew began to affect Jamaica and Haiti as it approached from the south. The system turned to the north and experienced slight weakening that night, but still maintained category 4 intensity. Matthew's structure did not change much the next day as it steadily approached the Greater Antilles. Extremely heavy rains began over Haiti on the 3rd and continued as the storm came closer and closer. Early on October 4, the center passed well to the east of Jamaica, though the island still experienced tropical storm conditions. Meanwhile, Matthew's pressure dropped to 934 mb, though the winds remained within category 4 intensity. Around 7:00 am EDT on October 4, Matthew made landfall in southwestern Haiti with maximum winds of 145 mph, the strongest hurricane to make landfall in the country in over 50 years.

Interaction with land began to slowly weaken the system, though the inner core remained largely intact. The cyclone emerged over water a few hours later and traversed the channel between Cuba and Haiti that day. It remained a category 4 with 140 mph winds when it made landfall near the eastern tip of Cuba at 8:00 pm EDT that evening. The cyclone stalled its northward motion slightly over land and weakened more substantially, becoming a category 3 storm early on October 5. By that time, it had again emerged over water and was entering the Bahamas. An amplifying ridge to the cyclone's east caused a northwest turn later that day. Meanwhile, Matthew began to recover from its land interactions that evening, with the pressure dropping and winds increasing as the eye passed through the Bahamas. Later on October 6, Matthew peaked as a category 4 once again. Rain bands had begun to affect Florida's east coast at this point and the cyclone continued to move closer to land, turning toward the north as it did so. Overnight, the center moved roughly parallel to the central and northern Florida coastline, with the outer eyewall bringing strong winds and heavy rains to the coastline from about 30 miles offshore.

Land interaction and increasing shear also started to weaken the storm as it moved northward. By the time it passed the coast of Georgia very early on October 8, the winds had diminished to category 2 strength. Matthew continued its turn and began to move northeast parallel to the U.S. coastline before finally crossing the shore late that morning as a category 1 hurricane in central South Carolina. Though the maximum winds had decreased by this point, very high levels of moisture in the atmosphere contributed to a huge rainfall event for the Carolina coasts, with over 10 inches of rain falling over a large swath of the region. In addition, the cyclone produced a large storm surge that inundated some low-lying areas. However, by this point, the hurricane was quickly acquiring extratropical characteristics, and transition was completed early on October 9. Though the system was moving eastward away from the coast, rains continued in the Outer Banks of North Carolina through the day before tapering off. The extratropical system was absorbed by a front the next day.

Hurricane Matthew was the first category 5 hurricane in the Atlantic in 9 years. The storm killed over 1000 people, a majority of whom lived in Haiti, making it the deadliest cyclone in the Atlantic since 2005. It also caused over five billion dollars in damages and was the costliest Atlantic hurricane since Hurricane Sandy of 2012. The above image shows the cyclone at peak intensity in the Caribbean Sea.

Matthew formed and strengthened unusually far south in the Caribbean before turning sharply northward and impacting the Greater Antilles, the Bahamas, and the U.S. east coast.

No comments: