Koppu Pulling Away from Philippines; TD 20-E May Threaten Mexico

Tropical Storm Koppu (known as Lando in the Philippines) is now arcing slowly around the northern tip of Luzon island after dumping prodigious amounts of rain over the last three days. At 15Z Tuesday (11:00 pm local time), Koppu was located at 19.2°N, 121.0°E, about 40 miles north of the north-central coast of Luzon. Koppu’s top sustained winds were down to 50 mph, but the storm should be able to maintain that strength for the next day as it crawls to the east. This will keep the island in moist westerly flow, so some additional rain is possible over already-soggy areas.


Figure 1. Residents remove mud near their house after heavy rains brought about by Typhoon Koppu inundated homes in Cabanatuan City, Nueva Ecija province, north of Manila on October 20, 2015, days after the typhoon hit Aurora province. Image credit: Ted Aljibe/AFP/Getty Images.


Figure 2. A man paddles a makeshift raft made from banana trunks over a flooded rice field at Barangay Camanutan, Isabela province, north of Manila on October 19, 2015, a day after Typhoon Koppu hit Aurora province. Residents of flooded farming villages in the Philippines were trapped on their rooftops October 19 and animals floated down fast-rising rivers. Image credit: STR/AFP/Getty Images.


Damage over the last three days from Koppu’s landfall and subsequent flooding is still being assessed, but weather.com reports that at least 28 people have died. Nearly all buildings and infrastructure sustained damage in the city of Casiguran, close to where Koppu came ashore. It appears that much of Koppu’s heavy rain stayed just offshore, but the upslope flow against the west side of Luzon’s mountains has been enough to generate immense local amounts, triggering mudslides and floods affecting the mountains as well as adjacent lowlands. The city of Baguio racked up 40.37” of rain through Tuesday afternoon, according to weather.com. A few miles south of Baguio, the massive San Roque Dam (the largest dam in the Philippines, and the world’s twentieth largest) had plenty of water to deal with. Weather records researcher Maximiliano Herrera, who maintains a comprehensive set of extreme temperature records on his website, pulled the following preliminary amounts for San Roque Dam from real-time data collected over a 24-hour period at the height of Koppu.

30 minutes: 66 mm (2.60”)
1 hour: 122 mm (4.80”)
6 hours: 483 mm (19.02”)
12 hours: 717 mm (28.23”)
18 hours: 1093 mm (43.03”)
24 hours: 1317 mm (51.85”)

If confirmed, these would set new 12- and 24-hour rainfall records for the Philippines, beating the records set during a July 1911 typhoon that dumped more than 2200 mm (87”) on Baguio in less than four days. Few other places on Earth have reported heavier amounts for half- and full-day periods. The world records of 1144 mm (45.04”) for 12 hours and 1825 mm (71.85”) for 24 hours were both set at the remote site of Foc-Foc on La Réunion island in the South Indian Ocean on January 7-8, 1966.


Figure 3. Latest satellite image of TD 20-E.

Tropical Depression 20-E forms; expected to hit Mexico as a hurricane
Tropical Depression 20-E formed at 11 am EDT Tuesday in Mexico's Pacific waters about about 445 east-southeast of Acapulco, Mexico, and appears poised to intensify into Hurricane Patricia later this week. TD 20-E is under light wind shear, has very warm waters of 30°C (86°F) to work with, and an atmosphere rich in moisture at mid-levels. These conditions should promote rapid intensification once TD 20-E gets well-organized and develops an inner core. Satellite loops on Tuesday morning showed that TD 20-E was poorly organized, with only a modest area of heavy thunderstorms and just the beginning of low-level spiral bands beginning to form. TD 20-E will move west-northwest, parallel to the coast today through Thursday, then turn abruptly inland to the north on Friday as it gets pulled northwards by a trough of low pressure.


Figure 4. MODIS image of Hurricane Olaf in the waters 1300 east-southeast of Hawaii as seen from NASA's Terra satellite on Monday, October 19, 2015 at 19:35 UTC. At the time, Olaf was a Category 4 storm with 135 mph winds. Image credit: NASA.

Eastern Pacific's Hurricane Olaf hits Category 4
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, becoming the the Northern Hemisphere's record-setting 21st Category 4 or stronger tropical cyclone of 2015 (previous record: eighteen in 2004, according to wunderblogger Dr. Phil Klotzbach.) Only one of those twenty Category 4 and 5 storms--Hurricane Joaquin--came from the Atlantic. Olaf is also notable for its low latitude. Coincidentally, the two most equatorward Category 4 cyclones on record for the Western Hemisphere share the same name: this year’s Hurricane Olaf (10.0°N) and 2005’s Cyclone Olaf (10.0°S).

By Tuesday morning at 5 am EDT, Olaf’s top sustained winds had increased to 150 mph, where they were holding through 11 am EDT. No other Northeast Pacific storm on record has been this strong any later than September 6, according to Klotzbach and Blake. An additional increase in winds of 10 mph would bring Olaf to Category 5 status, but Tuesday afternoon satellite loops showed a modest warming of the cloud tops, indicating that Olaf had likely peaked in strength. Olaf is likely to turn to the north by this weekend well east of Hawaii. Latest long-range forecasts from the GFS and European models keep Olaf moving to the northeast next week, away from Hawaii.

Accumulated cyclone energy: The Pacific has it
The hyperactive Pacific is reflected in year-to-date statistics on accumulated cyclone energy (ACE) compiled by Phil Klotzbach using data from the National Hurricane Center and Joint Typhoon Warning Center. ACE takes into account the strength as well as the longevity of tropical cyclones, but not their size. Through October 19, the Northeast Pacific ACE (184% of year-to-date average) was on track to end up in second place behind 1992; the Northwest Pacific ACE (189% of year-to-date average) was at record levels for the time of year; and the Central Pacific ACE was at an astounding 606% of its year-to-date average, partly a reflection of the many years that feature little activity in that basin. Within the next day or so, according to Klotzbach, Hurricane Olaf should push the Central Pacific past 1994 to set the basin’s all-time seasonal record. The North Atlantic is at a mere 62% of its year-to-date average, but the prolific Pacific has still pushed the entire Northern Hemisphere to a new year-to-date ACE record as of October 20, says Klotzbach.

Bob Henson and Jeff Masters