Tropical Storm Rammasun was upgraded to a typhoon at 5 a.m. Monday morning (EDT) and threatens the Philippines with heavy rain and 90 mile per hour winds.
But Rammasun could cause much more trouble in China after crossing the Philippines and the South China Sea.
A Tropical Storm, A Typhoon Or A Hurricane?
Rammasun is in the West Pacific Ocean and its winds, before its recent upgrade, were between 39 and 74 miles per hour, so it was properly classified a tropical storm.
It would have had the same designation in the eastern Pacific or Atlantic Ocean. Now that Rammasun’s winds are 75 miles per hour, it is classified as a typhoon. If it were in the eastern Pacific or the Atlantic it would be a hurricane.
There is no difference between a hurricane and a typhoon — the title just depends on the place where the storm happens to be.
Conditions Conducive To Hurricane (Typhoon) Formation
In order for a hurricane to form, the conditions have to be just right.
A hurricane requires:
- Warm ocean water of 80 degrees or higher — the higher the better.
- A vertical atmospheric structure with little variation of the wind with height (minimal wind shear)
The western tropical Pacific Ocean has the largest expanse of warm water on earth, and the water stays warm all year. The typhoon season runs from January 1 to December 31; the water is warm enough to support tropical cyclone formation in any month, and Rammasun is the ninth named storm of 2014.
In contrast, the Atlantic Basin (Atlantic Ocean, Caribbean Sea, and Gulf of Mexico) tropical storm season runs from June through November. Though storms have been recorded in every month, they are rare in winter and spring, as the water is generally below 80 degrees from December through May.
Will Rammasun Become A Typhoon As Strong As Neoguri?
Last week, Typhoon Neoguri reached super-typhoon strength (winds 150 miles per hour) and affected much of Japan. It was fortunate that before the storm reached populated areas, it was weakened by wind shear, colder water, and an intrusion of dry air.
Rammasun has been struggling to get organized because of wind shear. Conditions have now become more favorable for development, and Rammasun intensified overnight. However, it will not be as powerful as Neoguri, and certainly not as strong as Typhoon Haiyan, which struck the Philippines as a super-typhoon on November 8, 2013, killed over 6,000, and did over two billion dollars in damage.
Nevertheless, Rammasun could cause flooding and property damage as it passes close to the twin cities of Manila and Quezon, with a combined population of over four million.
Rammasun May Be More Dangerous After It Passes The Philippines
The Philippines are separated from China by the South China Sea, with water temperatures in the middle 80s. At this time, the forecast calls for only slight vertical wind shear after Rammasun passes the Philippines. Rapid strengthening is possible before the storm hits China.
Vertical Structure Of A Typhoon
In a well-developed or rapidly-strengthening typhoon, winds are spiraling in at the surface and spiraling out at jet stream level. The outflow aloft can easily be seen in satellite imagery. Rammasun’s current satellite image shows well-developed outflow on the south side, but a ragged appearance on the north side with outflow disrupted by vertical wind shear.
Where Will Rammasun Go?
The current forecast calls for Rammasun to hit the Philippines near Manila on Tuesday and make landfall in China just north of the island of Hainan by Friday. This will keep it well south of the important commercial centers of Hong Kong and Macau.
However, at this time range, the forecast cone widens. With warm water all around and little wind shear, the storm poses a threat to the entire coast of China from Hainan northward, as well as northern Vietnam. In addition, tropical systems can cause flooding in China far from the coast.
What’s Next For Pacific Ocean Typhoons?
The water remains very warm over the western Pacific Ocean.
No one can predict more than a few days in advance where a typhoon will strike, but it is a virtual certainty that this season will see much more activity.
Last year there were 30 named storms; Rammasun is the ninth this year. There will be more.