Bertha Headed Out to Sea; Iselle a Major Hurricane; Halong Hits Category 5

Tropical Storm Bertha was cruising northwest out of the Southeast Bahama Islands at 20 mph on Sunday morning, and was spreading gusty winds and heavy rain showers across the Southeast Bahamas and Turks and Caicos Islands. A personal weather station at Cockburn Harbour in the Caicos Islands reported a wind gust of 34 mph and 0.48" of rain as of noon Sunday. Rainfall amounts of 1 - 3" on Saturday and Sunday were common over Puerto Rico from Tropical Storm Bertha, and rainfall amounts of 6 - 8 inches over the center of the island brought several rivers close to flood stage. However, there were no reports of major damage or flooding from the storm, and Bertha's rains were welcome in an area that has suffered significant drought this year. Visible satellite loops on Sunday morning showed that Bertha was growing slightly more organized, with increased heavy thunderstorm activity and more low-level spiral bands, despite high wind shear of 25 knots. The atmosphere surrounding Bertha is now quite a bit more moist, and this extra moisture is likely allowing the storm to grow more organized. On Monday and Tuesday, Bertha is expected to encounter lower wind shear and a moister atmosphere, and these conditions may allow the storm to briefly intensify into a Category 1 hurricane. Bertha will not be a threat to any more land areas.


Figure 1. Rainfall amounts over Puerto Rico and the Virgin Islands from Tropical Storm Bertha. Image credit: National Weather Service.

Hurricane Iselle becomes 3rd major hurricane of 2014 in the Eastern Pacific
In the Eastern Pacific, Hurricane Iselle put on a bout of rapid intensification that brought the storm to Category 3 strength with 115 mph winds at 11 am EDT on Sunday. Iselle is headed westwards towards Hawaii, and could affect the Hawaiian Islands as a tropical storm by Thursday night. Satellite images show that Iselle has developed impressive symmetry and a large eye. Wind shear is expected to stay light to moderate for the next five days, but ocean temperatures will slowly cool to 26°C and the atmosphere will dry significant by Wednesday. Iselle is likely to slowly weaken beginning on Monday, but will probably remain a hurricane through Wednesday. The NOAA Hurricane Hunters' jet is scheduled to fly a dropsonde mission on Tuesday evening out of Honolulu, and an Air Force hurricane hunter aircraft is scheduled to fly a low-level mission into the hurricane early Wednesday morning. It's been a very active hurricane season in the Eastern Pacific, which has seen 9 named storms, 4 hurricanes, and 3 intense hurricanes so far in 2014. On average, we expect to see 6 named storms, 3 hurricanes, and 1 intense hurricane by August 3 in the Eastern Pacific.


Figure 2. Latest satellite image of Iselle in the Eastern Pacific.

Super Typhoon Halong headed towards Japan
In the Western Pacific, Super Typhoon Halong put on an impressive burst of rapid intensification on Saturday, topping out as a mighty Category 5 super typhoon with 160 mph winds between 2 pm EDT Saturday - 2 am EDT Sunday. Halong weakened slightly to a Category 4 super typhoon with 150 mph winds at 8 am EDT on Sunday, due to an eyewall replacement cycle. Satellite loops show that Halong's eye has grown less distinct, but the typhoon still has a large area of very intense eyewall thunderstorms. The storm is expected to turn northwards today, and will encounter higher wind shear and cooler waters over the next few days, which will likely weaken the storm to Category 2 strength before is reaches Japan's Ryukyu Islands on Thursday.


Figure 3. Super Typhoon Halong at 08:32 UTC Sunday, August 3, 2014. At the time, Halong was at peak strength: a Category 5 storm with 160 mph winds. Image credit: NOAA/NESDIS.

Jeff Masters