| Above: Hurricane Lorenzo as seen by the MODIS instrument on NASA's Aqua satellite on Thursday afternoon, September 26, 2019. |
Despite being embedded in a relatively favorable environment with warm sea surface temperatures near 28.5°C (85°F) and moderate wind shear of 10 – 15 knots, Tropical Storm Karen remained a highly disorganized tropical storm on Thursday afternoon. Satellite images showed an elongated storm with only a minimal amount of heavy thunderstorms that were poorly organized.
Karen will continue heading north to north-northeast at about 10 mph through Friday morning, then slow to a crawl and perform a clockwise loop through the day Friday. By Saturday, when a ridge of high pressure to Karen’s north will force the storm to the west, Karen will see an increase in wind shear to 15 – 20 knots, which will drive very dry air to its north into the circulation. Our top global models for hurricane tracking all agree that Karen will not survive this double-whammy of high wind shear and dry air beyond Sunday, when Karen is expected to degenerate to a remnant low. Karen’s demise should come well before it reaches The Bahamas.
Epic #hurricane structure of #Lorenzo, fortunately not near land given its current intensity & size, though it's propagating large waves and could ultimately track over or near the Azores. And mesovortices in the eye are looking at you. pic.twitter.com/5xwhA0v9OV
— Stu Ostro (@StuOstro) September 26, 2019
Beastly Lorenzo churns in the Central Atlantic
Hurricane Lorenzo put on a spectacular show of rapid intensification rarely seen in the Central Atlantic, vaulting to Category 4 strength with 130 mph winds at 11 am EDT Thursday. Lorenzo is one of the largest and most powerful hurricanes of record for the central tropical Atlantic; according to NHC, the only comparable hurricane in recent times near Lorenzo’s location was Gabrielle of 1989, which peaked as a Category 4 hurricane with 145 mph winds at 55.7°W. Only one hurricane on record has reached Category 4 strength farther east than the 40.2°W longitude that Lorenzo did so at—Hurricane Julia of 2010, which hit Cat 4 strength at 32.2°W.
Hurricane Lorenzo reached category 4 intensity unusually far to the east. Most category 4 hurricanes reach such intensity west of Lorenzo's current position, and only Julia (2010) reached it farther east. pic.twitter.com/Q2u7WbVTP2
— Tomer Burg (@burgwx) September 26, 2019
Lorenzo’s ascension to major hurricane status gives the Atlantic 12 named storms, 5 hurricanes, 3 intense hurricanes, and an ACE index of 91 so far in 2019. An average season typically has 9 named storms, 4 hurricanes, 2 intense hurricanes, and an ACE index of 78 by September 26, so this season is above-average for activity in all metrics.
With light wind shear (near 5 knots) and warm sea-surface temperatures near 27 – 27.5°C (81 - 82°F) expected through Friday night, Lorenzo has the opportunity to strengthen further, and satellite images from Thursday afternoon showed the storm was likely growing even more intense. From a thermodynamic standpoint, the maximum potential intensity Lorenzo can reach is likely 145 – 155 mph—at the upper end of the Category 4 range.
Models agree that Lorenzo will carry out a classic recurving path over the central and eastern Atlantic and begin gradually weakening on Saturday, reaching the vicinity of the Azores Islands on Tuesday night. At that time, Lorenzo is likely to be a weakening Category 1 hurricane. Lorenzo will be a massive wave generator due to its high intensity, longevity, and huge size--Lorenzo’s diameter of tropical-storm-force winds extended out 350 miles from northwest to southeast at 11 am EDT Thursday.
Bob Henson contributed to this post.
