The Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) has officially declared the start of La Niña, which may initiate the northeast monsoon once it transitions from the southwest monsoon.
Dr. Esperanza Cayanan, PAGASA deputy administrator for Research and Development, said in a statement that based on the rainfall forecast, most parts of the country will likely receive near to above normal rainfall conditions from October 2021 to March 2022.
“La Niña is usually associated with above normal rainfall conditions across most areas of the country during the last quarter of the year and early months of the following year,” said the statement.
Four to six tropical cyclones which mostly are possible to make landfalls are expected to enter and develop in the Philippine Area of Responsibility (PAR).
The tropical cyclones may further enhance the northeast monsoon or amihan and could trigger floods, flashfloods, and rain-induced landslides over susceptible areas, particularly in the eastern sections of the country which normally receive greater amount of rainfall at this time of the year.
Adverse impacts are likely over vulnerable areas and sectors of the country.
The state weather bureau stated that the recent oceanic and atmospheric conditions indicate La Nina has developed in the tropical Pacific.
Since July 2021, the sea surface temperatures in the central and equatorial Pacific started to cool and further temperature drop strengthened in September reaching La Nina threshold.
Meanwhile, PAGASA also announced the termination of the southwest monsoon or habagat as it significantly weakened based on the recent analysis over the past few days.
The strengthening of the high pressure area over mainland Asia and the expected northeasterly surge over Northern Luzon within the next five days confirms the gradual changing of the season, PAGASA added.
“With these development, the SWM season, locally known as “habagat” is now officially over. This means that the season in the Philippines is now in the process of transition, which will lead to the gradual onset of the Northeast Monsoon (NEM) in the coming weeks,” it added.
PAGASA advised all concerned government agencies and the public to take precautionary measures to mitigate the potential impacts of this event.