Infrared satellite image of Tropical Cyclone Pam on Wednesday. (NOAA)

The South Pacific islands of Vanuatu and Fiji are preparing for the impacts of Tropical Cyclone Pam, a powerful storm that is expected to intensify even further by Thursday evening as it approaches the islands.

On Wednesday, Tropical Cyclone Pam is a very large and intense tropical cyclone, with sustained winds of 135 mph — the equivalent of a category 4 hurricane. The cyclone underwent a period of rapid intensification  Tuesday, strengthening from a category 2 to a category 4 in under 24 hours. The Joint Typhoon Warning Center is forecasting continued intensification, reaching category 5 sustained winds of near 165 mph as it makes its closest approach to the islands of Vanuatu.

On Tuesday, global forecast models were predicting that the tropical cyclone would drop to an intensely low pressure of less than 880 millibars, but have since backed off on the extreme forecast. “These models are not known for making reliable intensity forecasts, and are generally disregarded by NHC for intensity forecasts in the Atlantic and Eastern Pacific,” writes Weather Underground’s Jeff Masters. “The HWRF model, which is one of our better intensity forecast models, predicted with its 06Z (2 am EDT) Wednesday run that Pam would reach a central pressure of 907 mb by Friday, which would make it a still-formidable Category 5 cyclone.”

On its current forecast track, Pam is expected to hammer the Vanuatu islands as it sweeps by as a category 5. Even if the storm doesn’t make landfall, it could still batter the islands with sustained winds up to 80 or 90 mph, and stronger gusts.

(Weather Underground)

Speaking with the Bureau of Meteorology’s head of operations, Andrew Tupper, Australia’s ABC News writes that the islands of the South Pacific are on high alert as the cyclone approaches:

“This is actually the most significant cyclone of all in terms of its size, which is very large, and its intensity,” Mr Tupper said.

“It’s forecast to thread the needle between Vanuatu and Fiji as it moves south, but probably a little bit too close to Vanuatu for anybody’s liking.”

UNICEF Pacific said it would meet with Vanuatu’s national disaster management team  Wednesday to discuss cyclone preparations.

A heavy rain and gale wind warning is also in place for Fiji. Shipping vessels have been ordered to stay in port, while residents in Fiji have been urged not to head out to sea this week.

Pam’s main rain bands and wind field could reach the northern islands of Vanuatu as early as Wednesday night, eastern time.