Saturday, October 12, 2013

Morning Before Cyclone Phailin Landfall Update: Dr. Jeff Masters' WunderBlog

Extremely dangerous Tropical Cyclone Phailin has maintained Category 5 strength for six hours, and is expected to remain a Category 5 storm until it is just a few hours from landfall on the northeast coast of India on the Bay of Bengal, according to the 5 pm EDT Friday advisory from the Joint Typhoon Warning Center.

Phailin put on a phenomenal burst of rapid intensification on Thursday, going from a tropical storm with 65 mph winds to a top-end Category 4 storm with 155 mph winds in just 24 hours, and is now at peak strength of 160 mph, tying it with Super Typhoon Usagi as Earth's strongest tropical cyclone of 2013.

Satellite images show that Phailin maintained very intense thunderstorms with cold cloud tops in its eyewall, with the 5 pm EDT Friday satellite estimate of Phailin's central pressure at 911 mb. This makes Phailin equal in strength to the great 1999 Odisha Cyclone, which killed 9,658 people in India's Odisha province. Radar out of Visakhapanam, India shows that heavy rains from the outer bands of Phailin are already affecting the coast, and these bands were bringing rainfall rates of over an inch per hour, as estimated by microwave data from 18 UTC Friday.

Phailin is over ocean waters that have warmed since Thursday, and are now 29 - 30°C. These warm waters extend to a lesser depth than before, and ocean heat content has dropped to a moderate 20 - 40 kJ/cm^2. Wind shear remains low, 5 - 10 knots, and Phailin has strong upper-level outflow, thanks to an anticyclone positioned in the upper atmosphere over the cyclone.

Figure 1. Microwave satellite image overlaid on an infrared satellite image of Tropical Cyclone Phailin, taken at approximately 18 UTC on October 11, 2013. At the time, Phailin was a Category 5 storm with winds of 160 mph.

Forecast for Phailin

Phailin is likely to be the strongest tropical cyclone to affect India in fourteen years, since the great 1999 Odisha Cyclone. The models are in tight agreement that Phailin will make landfall in Northeast India on Saturday between 09 - 15 UTC about 100 miles to the southwest of where the 1999 cyclone hit.

The India Meteorological Department (IMD) is predicting that a storm surge of up to 3.5 meters (eleven feet) will hit along a swath a coast to the right of where the center makes landfall. I expect that this is an underestimate, since the 1999 Odisha Cyclone brought a storm surge of 5.9 meters (19 feet) to the coast, and Phailin is larger in areal extent and just as strong.

The region of the coast where Phailin is expected to hit is not as low-lying, though, which should keep the death toll due to storm surge much lower compared to the 1999 Odisha Cyclone, where more than 70% of the deaths occurred due to the storm surge.

Deforestation of the coastal mangroves in the storm surge zone was associated with increased death toll in that storm, according to Das and Vincent (2009), who concluded, "villages with wider mangroves between them and the coast experienced significantly fewer deaths than ones with narrower or no mangroves.". I expect that Phailin will weaken slightly before hitting the coast, due to interaction with land, and hit as a Category 4 storm with winds of 145 - 155 mph. The 1999 Odisha Cyclone hit land with top winds of 155 mph.

Figure 2. Elevation of the Odisha region of India, with the track of the 1999 Odisha cyclone and forecast track of Phailin overlaid. Phailin is predicted to hit a region of the coast about 100 miles to the southwest of where the 1999 cyclone hit. The coast is not as low-lying to the southwest, which should result in a lower storm surge death toll. The greatest storm surge occurs along the coast to the right of where the center crosses.

Figure 3. The 00Z Friday rainfall forecast from the HWRF model calls for a significant swath of 8 - 16" of rain along the path of Phailin inland.
Phailin's heavy rains will be capable of causing very destructive flooding; the 00Z Friday rainfall forecast from the HWRF model (Figure 3) calls for a significant swath of 8 - 16" of rain along the path of Phailin inland. Rains from the 1999 Odisha cyclone killed more than 2,000 people in the town of Padmapur, located more than 150 miles from the coast. Deforestation was cited as a contributing cause to these destructive floods that killed 36% of the town's population. 

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