Sierra Madre ‘no shield’ vs typhoons – UP study

SANTIAGO CITY, Isabela, Philippines — The Sierra Madre mountain range may lessen typhoon winds in some parts of Luzon, but does not significantly weaken storms that cross the island, a study by University of the Philippines researchers found.

Researchers Gerry Bagtasa and Bernard Alan Racoma of the UP Institute of Environmental Science and Meteorology examined the effects of the Sierra Madre and Cordillera mountain ranges on 45 tropical cyclones that crossed Luzon from 2000 to 2020.

Using the Weather Research and Forecasting model, they ran simulations with the actual mountain terrain and compared these with scenarios in which either the Sierra Madre or Cordillera was flattened.

The results showed that neither mountain range significantly changed the intensity of tropical cyclones at landfall or during their initial passage across Luzon.

The Cordillera, however, was found to have a stronger overall effect in reducing wind hazards.

Its presence inhibited the re-intensification of tropical cyclones after they crossed Luzon and emerged over the West Philippine Sea, reducing accumulated wind-field energy by as much as 30 percent in parts of northern and Central Luzon.

The researchers also found that the Sierra Madre reduced rainfall in the Cagayan Valley from 10 to 59 percent, but enhanced it along the western slopes by 23 to 48 percent.