Typhoon Nuri Poised to Become an Alaskan Super Storm; Vance Drenching Mexico

Typhoon Nuri lost its "Super" designation Monday night, after the top winds fell below 150 mph, but remains poised to transition this weekend to one of the strongest extratropical storms ever to affect Alaska. Nuri intensified from a Category 1 storm with 85 mph winds to a very high-end Category 5 with 180 mph winds on Sunday, tying Super Typhoon Vongfong for strongest tropical cyclone of 2014 (as estimated by the Joint Typhoon Warning Center.) Satellite loops show that Nuri remains a formidable storm, with a large area of heavy thunderstorms with cold cloud tops and a prominent eye. Fortunately, Nuri is not expected to directly threaten any land areas, with the storm passing far enough from Japan on Thursday to keep the heavy rain area out to sea. However, once Nuri loses its tropical characteristics and moves into the Bering Sea to the west of Alaska on Friday, a very powerful jet stream will interact with ex-Nuri and cause it to rapidly intensify into one of the strongest low pressure systems ever observed in the Pacific Ocean. The GFS and European models continue to predict that the extratropical version of Super Typhoon Nuri will become a powerful sub-925 mb low with hurricane-force winds in the western Aleutian Islands on Friday night and Saturday morning. The 00Z Tuesday run of the European model predicted that ex-Nuri would bottom out at 920 mb at 06Z Saturday, a few hundred miles west of the westernmost Aleutian Islands. The 00Z Tuesday GFS model had the storm reaching 924 mb a few hundred miles northeast of there. According to wunderground's weather historian Christopher C. Burt, the all-time Alaska low pressure record is 926 mb at Dutch Harbor on October 25, 1977. Ex-Nuri would have a chance to beat that record if its center passed over one of the Aleutian islands on Saturday morning, but this morning's model runs predicted that the center would miss the westernmost Aleutian Island, Attu, by several hundred miles. Ex-Nuri will bring substantial impacts to the Aleutian Islands and coastal areas of southwest Alaska over the weekend, with the threat of damaging winds near hurricane force and a significant storm surge.


Figure 1. MODIS satellite image of Super Typhoon Nuri in the Pacific at 01:55 UTC November 4, 2014. At the time, Nuri was a weakening Category 4 storm with top sustained winds of 150 mph. Image credit: NASA.

Hurricane Vance a heavy rainfall threat to Mexico
Hurricane Vance in the Eastern Pacific off the coast of Mexico is steadily weakening as high wind shear of 35 - 40 knots tears into the storm. Satellite images show that Vance is barely recognizable as a hurricane, with an elongated disorganized appearance. Wind shear is expected to rise even higher before Vance reaches the Mexican coast late Wednesday morning, and this may be sufficient to tear Vance apart before landfall. Regardless of whether or not Vance makes it to the coast as a tropical storm, flooding rains will be the primary threat; heavy rains of 4 - 8" will affect the Mexican coast northwest of Puerto Vallarta on Tuesday and Wednesday. In their 10 am EST Tuesday Wind Probability Forecast, NHC gave a 3 - 12% chance that Vance would bring tropical storm-force winds of 39+ mph to Puerto Vallarta and the tip of the Baja Peninsula. Moisture from Vance is streaming to the northeast over Texas, and Flash Flood Watches are posted from Del Rio to Austin for 2 to 4 inches of rain, with isolated amounts up to 7 inches, though Wednesday morning.


Figure 2. MODIS satellite image of Hurricane Vance of the Pacific coast of Mexico at 20:50 UTC November 3, 2014. At the time, Vance was a peak-strength Category 2 storm with top sustained winds of 110 mph. Strong upper level winds from the southwest were disrupting the heavy thunderstorms on Vance's southwest side. Image credit: NASA.

Jeff Masters