Friday, October 2, 2009


Typhoon or Super Typhoon?

Pepeng is a very strong system. Depending on which weather bureau you rely on, Pepeng qualifies as either a strong Cat 3 or a weak Cat 4. The Joint Typhoon Warning Center of the US Navy shows that Pepeng has winds of about 225kph. Japanese Meteorological Agency, meanwhile, shows Pepeng has winds of around 160kph. To be classified as a Super Typhoon, a storm must have an average of at least 180kph within a 10-minute time frame. JMA and PAGASA uses this basis for their classification of a storm. JTWC, on the other hand, averages their winds in a period of just 1-minute, resulting to higher wind readings compared to PAGASA's. According to them, winds must be in excess of 250kph in order to be classified as a super typhoon. Now looking at the data, neither of the three (JMA, PAGASA, JTWC) has classified Typhoon Pepeng as a super typhoon.

However, should we be complacent about it? Absolutely not. Typhoon Pepeng is still strong and could cause massive damage in the provinces of Aurora, Isabela, and Cagayan.

Latest Data

Typhoon Pepeng was last spotted at around 430km east northeast of Manila. It has maximum wind speeds of about 185kph, extending to around 30km from the eye. It is moving WNW at 20kph.
In-depth Forecast

Typhoon Pepeng should make landfall in the province of Cagayan at around 2pm. Maximum winds at that time should be between 180-210kph. It should continue moving WNW and then take a turn to the NW as Typhoon Melor is now influencing Pepeng.

24hours (100309 2pm PST): Typhoon Pepeng just 60km east northeast of Tuguegarao. Winds from the NW in excess of 180kph is expected. Storm surges along the coast is expected, wave heights 3-6m. Heavy rainfall rates of about 60mm/hr is also expected. Widespread 30mm/hr rainfall is likely. (see wave and rainfall maps below)

36hours (100409 2am PST): Typhoon Pepeng should have weakened. Located at about 130km northeast of Laoag. Winds should have decreased to around 150-190kph. Flooding now a problem in many parts, as well as damaged properties. Cities along Northernmost Luzon should still expect winds 120-150kph from the NW.

48hours (100409 2pm PST): Forecasts during this time could change in the next 12 hours. Uncertainty in track past this time period. Typhoon Melor should enter PAR within this time frame, moving near Pepeng, therefore influencing its movement. Two solutions are likely, GFS and ECMWF have suggested that it could take a sudden turn to the NE; another solution, supported by the NOGAPS and CMC, suggest that Pepeng could remain quasi-stationary. If that happens, it could re-intensify again in the Luzon Strait. Either way, tropical force winds and occassional moderate-heavy rains should be expected in the provinces of Batanes, Cagayan, and northern Ilocos Norte.

Expected Signal Warnings effective until 100309 2pm PST
Wave Heights (Valid Until 100309 2pm PST)

Accumulative Rainfall Forecast for the next 24-36 hours
100209 530PM PST

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