Super Typhoon Koppu Could Hit Philippines as a Cat 5

Intensifying Super Typhoon Koppu is pounding the Philippines' eastern Luzon Island with torrential rains as the storm crawls west-northwest at 6 mph. Koppu (called "Lando" locally in the Philippines) could achieve Category 5 status before making landfall between 2 - 6 pm EDT Saturday. At 8 am EDT Saturday, the Joint Typhoon Warning Center estimated Koppu was a Category 4 super typhoon with top winds of 150 mph, and the Japan Meteorological Agency estimated a central pressure of 930 mb. According to wunderblogger Dr. Phil Klotzbach, Koppu is the nineteenth Category 4 or 5 tropical cyclone this year in the Northern Hemisphere, setting a new record for these most powerful of storms. The previous record was eighteen such storms in 2004. Satellite loops on Saturday morning showed that Koppu had an impressive ring of eyewall clouds with very cold cloud tops that extended high into the atmosphere, and a prominent 23-mile diameter eye. The combination of low wind shear, warm ocean waters that extend to great depth and the presence of two impressive upper level outflow channels will support continued intensification right up until landfall. Extreme winds, a large storm surge, and heavy rains are all major threats from Koppu, but it is the storm's rains that will cause most of the storm's destruction. Recent satellite estimates showed Koppu's maximum rainfall rate was likely 20 inches of rain per 24 hours.


Figure 1. Typhoon Koppu as seen by Japan's Himawari satellite on Saturday, October 17, 2015 at 02:19 UTC (10:19 pm EDT Friday.) At the time, Koppu was an intensifying Category 3 storm with 120 mph winds. Image credit: NOAA/RAMMB and Japan Meteorological Agency.


Figure 2. Super Typhoon Koppu as seen by Philippines radar at 11:15 am EDT Saturday, October 17, 2015. Image credit: PAGASA.

Forecast for Koppu: an extreme rainfall nightmare
Unfortunately for the Philippines, Koppu is moving very slowly, which will lead to extremely high rainfall rates. Koppu will slow down further after landfall, and spend at least three days over northern Luzon Island. With water temperatures an unusually warm 30 - 31°C (86 - 88°F) in the waters surrounding Luzon--about 1°C (1.8°F) above average--the typhoon will be able to pull in tremendous amounts of water vapor from the oceans, resulting in widespread rains of over two feet falling on Luzon Island. More than four feet of rain will likely fall in some mountainous areas, and rainfall amounts of this magnitude are likely to cause devastating flooding. The latest 06Z (2 am EDT) Saturday run of the GFS model shows Koppu spending a full five days over Luzon, which would result in even more disastrous rainfall amounts than described here. The capital of Manila (population 12 million) lies right at the edge of where the most extreme rains of at least a foot will fall, so hopefully the monetary damage from the flooding will stay below a billion dollars.


Figure 3. Predicted rainfall (inches) for the 24-hour period 2 am EDT Saturday - 2 am EDT Sunday, October 18, 2015, based on satellite-derived rainfall estimates. An area of more than 20 inches of rain in 24 hours (pink colors) was predicted just offshore of the Philippines' Luzon Island. Image credit: NOAA/NESDIS.


Figure 4. Predicted 5-day rainfall amounts from Typhoon Koppu from the 00Z Saturday (8 pm EDT Friday) October 17, 2015 run of the GFDL model. Widespread rainfall amounts in excess of two feet (orange and red colors) were predicted for the Philippines' Luzon Island, north of the capital of Manila. Image credit: NOAA/GFDL.

Best historical analogue for Koppu's rains: the historic rains of August, 2013
The best historical analogue for the rains expected from Koppu may be an extreme monsoon rainfall event on August 18 - 21, 2013, which was enhanced by moisture from Tropical Storm Trami. Up to 600 millimeters (23.5 inches) of rain fell during one 24-hour stretch, and about 60% of metro Manila was under water at one point. At least 27 people died, and damage was estimated at $2.2 billion, making it the Philippines' second most expensive disaster in their history. Another possible analogue: a 1911 typhoon dumped more than 2,200 millimeters (87 inches) of rain in four days in Baguio, in a mountainous region of Luzon Island, according to TWC's Nick Wiltgen.

The top five most expensive disasters in Philippines history, according to EM-DAT (dollar values unadjusted for inflation):

1) Super Typhoon Haiyan, 11/8/2013, $10 billion
2) Monsoon rains increased by Tropical Storm Trami, 8/20/2013, $2.19 billion
3) Super Typhoon Bopha, 12/4/2012, $898 million
4) Super Typhoon Rammasun, 7/15/2014, $821 million
5) Tropical Storm Nina, 9/4/1995, $700 million

Storm chaser James Reynolds is on Luzon, and will be posting updates on his experiences via his Twitter feed.

Elsewhere in the Pacific: Typhoon Champi, Tropical Storm Olaf, and Tropical Cyclone Two
Category 2 Typhoon Champi is expected to intensify into a Category 4 storm by Sunday, becoming the Northern Hemisphere's record-setting twentieth Category 4 or stronger tropical cyclone of 2015. Champi is headed northwest, and will turn to the north and northeast on Sunday and Monday. By Tuesday, a weakening Champi may pass close enough to Iwo Jima to bring hurricane-force winds to that island.

In the Eastern Pacific, Tropical Storm Olaf is steadily organizing as it heads west at 12 mph towards Hawaii. Olaf is predicted to reach major hurricane strength by Monday, but will turn to the northwest well before reaching Hawaii, eventually dying in the waters between Hawaii and California more than a week from now. Olaf is not a threat to any land areas.

In the South Pacific, Tropical Cyclone Two, the second tropical cyclone of the 2015 - 2016 season, is expected to dissipate in the waters about 300 miles west of Fiji on Saturday night.


Figure 5. Latest satellite image of 92L.

Development of 92L in Gulf of Mexico possible
An area of showers and thunderstorms (Invest 92L) extending from the northwestern Caribbean Sea through the southern Yucatan Peninsula at 8 am EDT Saturday was associated with an area of low pressure located over central Belize. This low will move slowly west-northwest at about 5 mph, and may emerge over the southern Gulf of Mexico's Bay of Campeche on Sunday or Monday. The disturbance's proximity to land, and competition from a separate tropical disturbance in the Eastern Pacific that NHC is giving 5-day development odds of 80% to, will keep the odds of 92L's development low. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave 92L 2-day and 5-day odds of development of 10% and 20%, respectively. Moisture from 92L is likely to spread northwards across Texas late in the week, bringing heavy rains.

Jeff Masters