A Busy Northern Hemisphere: Five Named Systems in the Atlantic and Pacific

The “string of pearls” effect continued on Tuesday morning over the Northern Hemisphere, with an arc of tropical cyclones extending from south of Japan to east of the United States. According to Eric Blake (National Hurricane Center) and Phil Klotzbach (Colorado State University), this is the first year on record with so many named systems to date for the Atlantic, Central Pacific and Eastern Pacific combined: a total of 11 as of Monday, July 13, with the previous record of 10 occuring in 2012.


Figure 1. A multispectral (RGB) image of Tropical Storm Claudette, from 9:45 am EDT Tuesday, reveals the highly offset nature of the system. Image credit: NOAA/NESDIS.

A weakening Claudette spins into the northwest Atlantic
Tropical Storm Claudette, which formed quickly on Monday, is losing its tropical characteristics just about as quickly today. As of 8:00 am EDT Tuesday, Claudette was located about 250 miles south-southeast of Halifax, Nova Scotia, with peak sustained winds down to 40 mph, the minimal strength for tropical-storm status. High wind shear (more than 35 mph) is taking its toll on Claudette, with the storm’s paltry convection shoved well northeast of the circulation. Claudette has been riding the north edge of the Gulf Stream, where sea-surface temperatures (SSTs) have been 1 – 2°C above average. However, the system is quickly moving toward much cooler waters, and NHC is predicting that Claudette will become post-tropical by Tuesday night.

Across the deep Atlantic tropics and the Caribbean, conditions remain very unfavorable for tropical cyclone formation. SSTs are close to 1°C below average, and El Niño is contributing to high values of deep-layer wind shear (generally above 30 knots, with widespread pockets of greater than 50 knots). At least for the time being, whatever systems manage to claw their way into existence in the Atlantic are most likely to form in the subtropics, north of at least 20°N.


Figure 2. Wind shear is producing hostile conditions for tropical storm development over much of the Atlantic south of 30°N. Image credit: CIMSS/University of Wisconsin.

Nangka churns its way toward Japan
A potent Typhoon Nangka continues to organize as it moves north-northwest at about 8 mph across the Northwest Pacific toward Japan. As of 1200 GMT (8:00 am EDT) on Tuesday, Nangka was located about 800 miles south-southwest of Tokyo, with sustained winds of 105 mph. Wind shear is low along Nangka’s immediate path (5 -10 knots) and SSTs above 26°C (79°F) support strengthening. An unusual double-eyewall structure developed on Tuesday local time as part of an eyewall intensification process, which delayed further strengthening in spite of the otherwise favorable conditions. In addition, the ridge north of Nangka that’s keeping it from moving northeast is also feeding dry air into the system, tamping down on its intensification rate. This strengthening ridge should cause Nangka to bend toward the northwest as it approaches Japan. Though the ECMWF model keeps Nangka stronger than the GFS, both models consistently point toward a likely landfall in or near Japan’s large western islands of Kyushu and Shikoku, with impacts possibly extending east toward Honshu and the large cities of Kyoto, Kobe, and Osaka. As with the U.S. mid-Atlantic coast, most typhoons approaching Japan are moving toward the northeast. The currently projected motion toward the north-northwest, more perpendicular to Japan’s southern coastlines, would bolster Nangka’s destructive power, much as Hurricane Sandy’s unusual approach from the southeast in 2012 increased the damage it wreaked on New York and New Jersey.


Figure 3. Infrared imagery from the Himawari-8 satellite revealed an unusually well-defined double eyewall structure in Typhoon Nangka on Tuesday local time, with strong subsidence on either side of the inner and outer eyewalls and a resulting “moat” (grey semicircle) evident between the two. This image was collected at 1300 GMT on July 13. Image credit: SSEC/University of Wisconsin.

Elsewhere in the Pacific
In the Northwest Pacific, Typhoon Halola continues a gradual strengthening, with peak winds of close to 100 mph as of 1200 GMT Tuesday. Halola was located about 475 nautical miles east-southeast of Wake Island, and the Joint Typhoon Warning Center predicts that Halola will pass just south of Wake Island on Thursday local time as a strong Category 2 typhoon. Such a trajectory would place the island in the dangerous right eyewall of the typhoon. The last major hurricane to strike Wake Island was Ioke, which brought sustained winds estimated at 155 mph and a minimum central pressure measured at 934 mb on August 31, 2006.

In the Eastern Pacific, we have two active named storms, neither of which is expected to hit land: Tropical Storm Enrique and Hurricane Dolores. Now packing sustained winds of 85 mph, Dolores is predicted to hit a peak intensity of at least Category 3 strength by Thursday as it gradually moves away from the Mexican coastline. Meanwhile, Enrique will struggle to maintain itself as a minimal tropical storm over the next couple of days, with current sustained winds at 45 mph and gradual weakening predicted.

I’ll have an update later today on this week's multiday severe weather episode across the Midwest and mid-Atlantic.

Bob Henson