Patricia Threatens Mexico; Big Surf in Hawaii From Olaf; Koppu Finally Dies

Tropical Storm Patricia formed on Tuesday evening in Mexico's Pacific waters about about 400 miles east-southeast of Acapulco, Mexico, becoming the 16th named storm of this unusually active Eastern Pacific hurricane season. Satellite loops on Wednesday morning showed that Patricia was a poorly organized minimal tropical storm with 40 mph winds, with no well-formed low-level spiral bands and a modest area of heavy thunderstorms. Radar images from the Acapulco radar showed that Patricia's main heavy thunderstorm activity was offshore, though a few bands of heavy rain were affecting the coast. Patricia is under light wind shear, has very warm waters of 30°C (86°F) to work with, and an atmosphere rich in moisture (>80% relative humidity) at mid-levels. These conditions should promote rapid intensification once Patricia gets well-organized and develops an inner core. Patricia will move to the west, roughly parallel to the coast, today through Thursday, then turn abruptly to the north on Friday as it gets pulled northwards by a trough of low pressure. The computer models all agree that this will result in Patricia making landfall in Southwest Mexico on Friday, possibly as a hurricane. If Patricia does make landfall as a hurricane, it would become the fifth latest Pacific hurricane to strike Mexico since records began in 1949, according to a database of Eastern Pacific hurricanes maintained by NOAA's Coastal Services Center. The only Pacific hurricanes to strike Mexico later than October 23 were Category 4 Hurricane Kenna of 2002 (which struck on October 25) and Category 3 Hurricane Olivia of 1975 (also an October 25 landfall), Category 1 Hurricane Rick (November 10, 1997) and Category 1 Hurricane Tara (November 11, 1961.)


Figure 1. Latest satellite image of Patricia.

Central Pacific's Hurricane Olaf maintains Category 4 strength
Hurricane Olaf intensified into a major Category 4 hurricane on Monday at 5 pm EDT in the waters about 1200 miles east-southeast of Hawaii, and maintained Category 4 strength through Wednesday morning at 5 am EDT. Wednesday morning satellite loops showed Olaf was a bit weaker than its 150 mph peak strength on Tuesday, and the storm is likely to continue to weaken as it turns north late this week, passing about 600 miles east of Hawaii on Saturday morning. While the storm will not bring strong winds or heavy rain to the islands, Olaf is generating high surf, and a High Surf Advisory is posted for Hawaii's Big Island for waves of 6 - 10 feet. Latest long-range forecasts from the GFS and European models keep Olaf moving to the northeast next week, away from Hawaii. Some of the long-range outlooks from the GFS model have shown Olaf (or its extratropical remnant) getting unusually close to Northern California 7 - 9 days from now, but these forecasts have not been consistent.


Figure 2. MODIS image of Hurricane Olaf in the waters east-southeast of Hawaii as seen from NASA's Aqua satellite on Tuesday, October 20, 2015. At the time, Olaf was at peak strength--a Category 4 storm with 150 mph winds. Image credit: NASA.

Typhoon Koppu finally dies
High wind shear and interaction with land have finally done in Typhoon Koppu (known as Lando in the Philippines), whose remnants are still bringing some heavy rain to northern Luzon Island in the Philippines. According to BBC News, Koppu killed at least 39 people and left behind $141 million in agricultural damage. Weather.com has a detailed summary of Koppu's impacts on the Philippines.


Figure 3. Thousands of homes were damaged in Casiguaran, Philippines during Typhoon Koppu. (@jeffcanoy/instagram) 

I'll have a new post by 1 pm EDT today, after NOAA releases its global September weather summary.