NWS: Wind forecasts were ‘too low’

The National Weather Service in Guam said they did not expect Typhoon Soudelor to be as strong as it was and that wind forecasts were “too low”—substantiating reports on the ground of stronger winds and speculations of those who woke up to Soudelor’s destruction that the 120 miles per hour gusts that was earlier predicted was wrong.

“We did not expect the typhoon to be this strong when it hit Saipan,” Chip Guard, Warning Coordination meteorologist of the NWS Forecast Office Guam told Saipan Tribune yesterday.

“Our wind forecasts were the highest of the weather prediction agencies and they were too low,” he added.

When asked about the actual measurements of the winds and gusts that Saipan experienced, Guard said they are not sure yet but that winds were stronger.

“We do believe that the winds were stronger but are not sure at this point how much stronger,” he said.

Guard said the update of 105 miles per hour maximum winds and 120 miles per hour gusts “came in just a few hours before the storm struck.”

Guard and another meteorologist, Dr. Mark Lander of the Water and Environmental Research Institute, will be visiting Saipan next week to conduct an assessment of the strength of the typhoon.

“We won’t know the intensity of the typhoon until we assess the damages, look at all of the data, apply some hard science, and eventually determine the likely wind speed. It will most probably be a range of wind speeds and we hope to narrow that range. We do hope to have a good estimate soon,” Guard said.

214 mph gusts

Dr. Tony Stearns, a long-time weather enthusiast who has a weather station set up at his residence on Capitol Hill for some years, was able to record way higher sustained winds and gusts when Typhoon Soudelor passed by Saipan Sunday night.

He said winds started picking up at 6pm with about 60 to 70mph gusts and an average of 50 to 70mph.

“And then the winds went down to 20 to 30 miles an hour range and I thought we may be having the eye passing us,” Stearns said.

Half an hour later, Stearns noted the winds started picking up again from 30mph all the way to 140mph.

“Within about half an hour, sustained winds at 10-minute average were between 130 to 145 mph,” Stearns said, noting the time between 11pm to midnight.

Given that Stearn’s weather station records sustained winds at 10-minute average, it should have been lower than that of NWS as it observes sustained winds at one-minute averages, which gives roughly 12 percent higher values.

The maximum gust that Stearn’s Davis weather station recorded was at 214 mph—almost double than that of the last update from NWS before Soudelor hit.

“I’m pretty sure it was accurate given the destruction that we have and what I know about the weather and what I’ve seen before at the weather station,” Stearns told the Saipan Tribune.

Stearns also noted that their location may have contributed to the amount of wind that they received.

“We always know that we get more wind on Wireless [Ridge] than most of the people get because we’re so exposed,” he said.

Luckily, Stearn’s station didn’t get blown away while the gauges at the airport went down.

“The gauges over at the airport went down as the winds picked up and if you look online it stopped at about 91,” special assistant for Homeland Security and Emergency Management Marvin Seman said.

“We feel that regardless of the wind, this storm made a great impact in the community,” he added.

The Weather Service said they will be evaluating wind observations that were taken on Saipan.

“Many things have to be considered, especially with regards to the terrain. Saipan is a ‘mountainous’ location,” Guard said.

Ear-popping pressure changes

Stearn’s station was able to record pressure that was severely low at 934 millibars.

NWS wasn’t also sure of how low the pressure got but they said it is one of the things that they will be trying to determine.

Aside from causing ears to pop, rapid changes in pressure also causes much damage to structures according to Guard.

“The rapid pressure changes come from the differences between the peak and lull of the wind gusts. That is what makes your ears pop. That is also what causes much of the damage to wooden and metal structures,” Guard said.

Soudelor went from being a typhoon to super typhoon and became the strongest cyclone in the world this year after it passed the CNMI. It is now in the Philippine’s area of responsibility on its way to Taiwan.

Enough warning

Asked if the government gave sufficient warning to the public prior to Typhoon Soudelor’s arrival, Seman said “yes.”

He noted that they set the Typhoon Conditions because they were expecting its strength. He added that the typhoon going through Saipan was “the biggest factor.”

NWS noted that Soudelor’s size was also unusual.

“The more unusual aspect of this storm was its very small size. The eye and the eye wall cloud were about 15 miles across total. Damaging winds did not extend much beyond that distance,” Guard added.

CNMI was also directly hit by a strong typhoon, Super Typhoon Kim, in December 1986 and Typhoon Jean in 1968.