Placed on red alert were Metro Manila and the regions of Calabarzon, Mimaropa, Bicol, Western Visayas, Central Visayas, Eastern Visayas, Caraga and Northern Mindanao, said NDRRMC spokesperson Major Rey Balido.
Under this status, disaster units are advised to take pre-emptive evacuation of residents and for local government units to prepare shelters and preposition relief goods.
Haiyan could carry winds of up to 241 kilometers per hour by Friday night before weakening a bit to 213 kph by Saturday or after crossing the country.
Hawaii-based Joint Typhoon Warning Center (JTWC) classifies a super typhoon if center winds reach 241 kph or above.
"Rain and increasing wind will reach the central Philippines Friday afternoon and conditions will deteriorate from east to west Friday night into early Saturday as the powerful typhoon crosses the islands," said meteorologist Eric Leister of accuweather.com.
The Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) said it will likely raise public storm signal number 4 in areas to be visited by Haiyan, a Chinese term for petrel or a kind of seabird.
The condition is characterized by "very strong winds" of more than 185 kph that may be expected in at least 12 hours.
The winds may bring extensive damage to coconut plantation, houses and buildings, uproot many large trees and cut power lines.
"Emerging into the South China Sea later Saturday, Haiyan will remain a dangerous cyclone as it continues to move to the west-northwest. The eventual track of Haiyan will bring the storm toward Vietnam by late Sunday into Monday," said Leister.
Haiyan will be the 24th storm to enter the country this year. (Virgil Lopez/Sunnex)