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On December 16, 1997, Andersen Air Force Base, on the Pacific island of Guam, reported a gust of 236 miles per hour. If verified, the event would have established a new world record for a surface gust a matter of scientific interest and of special interest to the Mount Washington Observatory, since the reported gust would have eclipsed the existing Mount Washington record by a small margin. As investigation of the Guam report proceeded, it became evident that the claim of a 236 mile per hour gust could not be substantiated.

We include here some reports from that time, illustrating the early reports of the Guam gust and the follow-up to the event, including the final statement of the National Climate Extremes Committee which concluded that the report of a 236 mile per hour gust was not reliable.

Initial Report posted 12/18/97

A New Record? - posted 12/18/97

Anemometer Information - posted 12/20/97

Growing skepticism posted 12/21/97

National Extremes Committee Update - posted 1/9/98

Official report of the Joint Typhoon Warning Center - posted 1/13/98

Report of the Pacific Daily News - posted 2/13/98

Final Statement from National Climate Extremes Committee - posted 3/11/98

References

Initial Reports

posted 12/18/97

On Wednesday, December 17, 1997 at 0631 GMT (1 am Eastern Standard Time) a wind gust measurement of 236 miles per hour was taken by instruments at Andersen Air Force, on the island of Guam. This gust was due to Typhoon Paka, which devastated this small Pacific island. If this measurement is accurate, it would break the existing record for the highest surface wind ever recorded anywhere on the planet; a gust of 231 mph clocked on Mount Washington on April 12, 1934.

A New Record?

posted 12/18/97

Immediately folowing the event, there a number of questions about the validity of this measurement. Delores Clark of The National Weather Service (NWS) Pacific Region Office in Hawaii said "We've been quoted as giving that wind speed, but that's not true." She also reported "None of our forecasters think it was that high, and we've been unable to confirm it." The NWS office in Gray ME, which has fielded many questions about the event states that "an NWS Team will analyze the storm and wind data and if the wind speed appears accurate, they will submit their findings to the National Climate Extremes Committee for consideration as a new national/world's record." The mandate and functional responsibilities of the National Climate Extremes Committee were determined only last month (November, 1997) by the National Climatic Data Center.

Anemometer Information

posted 12/20/97

According to information supplied by Rodger Brown of the National Severe Storms Laboratory, the anemometer used at Andersen Air Force Base on Guam is a FMQ-13 hot-wire anemometer. "The speed accuracy in the 99-150 knot range is +/- 15% and no accuracy is listed for speeds above 150 knots. With this accuracy, the 205 knot (236 mile per hour) measurement has a lot of uncertainty." Brown adds "I would think that the only way the measurement could stand would be to calibrate that particular instrument in a wind tunnel like was done in 1934."

The anemometer used on Mount Washington in 1934, known as the Number 2 Heated Anemometer, was tested in 1933 in two National Bureau of Standards wind tunnels, creating a calibration curve that allowed the Observers to calculate the wind speed immediately. After the record wind of April 1934, the anemometer was retested, to determine if there had been any change in the performance of the instrument since the earlier tests. The second tests indicated that the rotor was turning slightly slower (generally less than 3%) than in the first set of tests. This means that if past records were corrected on the basis of the second tests, the true wind velocities computed for the record would be somewhat higher than preciously claimed. It was recommended by the U.S. Weather Bureau that it would be both conservative and best for future observations to be calculated from the original calibration data.

Growing Skepticism

posted 12/21/97

In the days since the 236 mile per hour gust was reported, concern about the validity of the measurement has been growing, prompting investigation into the event. Stu Ostro of The Weather Channel has had contact with several people in Guam, and reports the following:

"Being skeptical about the validity of the 236 mph wind gust observation from Guam for a number of reasons, I called the Joint Typhoon Warning Center Tuesday evening EST. They indicated that they also believed the report was in error."

"They referred me to Andersen AFB ... the person to whom I spoke there was hesitant to categorically confirm or refute pending a review of the data, but indicated that there were power surges at the time, as well as "error codes" being received from the instrumentation (by the way, not a "cup"-type anemometer ... it's an "FMQ13"... anyone familiar with that?)."

"She in turn referred me to someone at the command post. He also confirmed that they believed there were problems with the data. However, during our conversation, a call came in on the other line suggesting that it was after the gust to 236 that the equipment had problems. He also referred to a sustained wind of 175 kts (201 mph) at the time whereas on the ob sent out on the wire it was only 84 kts (97 mph). (In one sense, that would perhaps make it more believable - less of a gust factor. On the other hand, a sustained wind of 200 mph at that point seems highly implausible.)"

"This Wed eve I spoke again to one of the people at Andersen AFB closest to the issue (same one as Tue) to see whether they had any new thoughts. The answer was no. The official line is still that there were power surges at the time and it is suspected that there were problems with the data. What a different person referred to last night as a late sentiment of there having not been any equipment issues at the time was clarified. At the precise moment of the gust, the equipment appeared to be operating okay, so therefore the decision was made at the time to release the ob to the circuit. But overall it was in the midst of these power surges and error codes, hence while there has been no categorical refutation, there has also been absolutely NO official confirmation of its validity. (She also had no idea where the notion of sustained winds of 200 mph originated and did clearly debunk that.)"

"In fact, she said they were aware of the fact that some other stateside media had picked up on this gust and were stating that a new world record had been set or at least citing the 236 mph without qualification, and encouraged TWC to let people know what the real story is. (Outside of this post to Wx-Talk and Wx-Chase, while we were still airing the Guam video on the cable network this evening we added some wording in the associated script to address the issue, and some OCMs have been commenting in other segments.)"

"She said that observers and meteorologists will be convening, hopefully within the next week or so, to review the data and issue a subsequent report. (One suspects that if the ob survives that phase, there will be further tests of the equipment and some politicking before it goes down in the books...)"

"I've left names and phone numbers out to avoid having them be deluged with calls. I myself was hesitant to call, and would like to mention that everyone with whom I spoke was extremely accomodating given the situation there - I'm sure they had a few other things to worry about! Their assistance is much appreciated."

"P.S. This is all interesting for aficionados (count me as one) of Mt. Washington and its 231 mph, but of course, that's the "official world record" of an actual anemometer measurement, not necessarily representative of the true "world record" highest wind speeds which occur on Earth - in the most violent tornadoes."

National Extremes Committee Update

posted 1/9/98

In early January, the following information was provided by Andy Hovritz of the National Weather Service. Hovritz is a member of the National Extremes Committee, which will determine whether or not the reported 236 mph wind will stand as a new world record.

The Pacific Region office of the National Weather Service is leading the Service Assessment report and there is also a Post-Storm Data Acquisition Team Report. The reports should be concluded in the 30-60 day time frame.

A video conference call was held on December 29, 1997, between the Pacific Region office (PR), the Tropical Prediction Center (TPC), the Operational Support Facility (OSF), and the National Climatic Data Center (NCDC). In this conference, PR indicated that the damage on Andersen is not reflective of the reported wind speed. However, the report did occur in the outer eyewall and there may have been a small vortex over a small area, creating a significant gust.

TPC will be analyzing the Level 4 data from the 88-D Doppler radar. The Office of Federal Coordination for Meteorology (OFCM) will be coordinating with the Air Force to perform a wind tunnel evaluation of the instrument.

Official Report of the Joint Typhoon Warning Center

posted 1/13/98

The Joint Typhoon Warning Center (JTWC) has issued an official report on Paka.

Part 3 of the report addresses the surface winds associated with Paka, and tries to determine the highest sustained winds and wind gusts that are likely to have occurred, based upon the available wind and pressure data. An excerpt of the report follows, with emphasis added by the author of this Mount Washington Observatory Web page.

3. Surface Wind Assessment

Considering the strength and duration of the Paka's surface winds, it is not surprising that the wind records for areas that experienced passage of the primary wall cloud were fragmentary. The approach taken with these incomplete and noisy raw data records was to work sustained wind observations against the peak wind gusts, using a standard gust factor of 1.20 to 1.25 over water (Atkinson, 1974) and 1.60 overland. For example, gusts to 120 knots over water would be associated with a sustained surface wind of 100 knots; overland gusts to 120 knots would relate to 75-knot sustained wind. This technique identifies the representative data, for example: Commercial Port NWS HANDAR at Apra Harbor reported sustained/peak gust of 100/149 knots which is plausible; the Andersen AFB anemometer recorded 96/205 knots which is not considered representative. The Commercial Port sensor failed after recording four hours of 135 to 149 knot gusts in the wall cloud, Andersen AFB sensor lost power during passage of the western wall cloud. Additionally, the NWS sensor at Tiyan lost power during the onset of the primary wall cloud, the NPMOCW/JTWC anemometer at Nimitz Hill failed at 103 knot before the wall cloud arrived, the wind bird at the Apra Harbor tide guage failed in the wall cloud, and the NWS HANDAR at the University of Guam, Mangilao weathered the storm to report a peak gust to 123 knots. In the final analysis the HANDAR instrument at Apra Harbor becomes the bench mark. It faithfully recorded peak gusts up to 149 knots until the winds began backing to the southwest, at which point it failed. This implies that the later southwesterly flow or second wind was stronger than the initial northwest to west wind (or first wind). This is borne out by the reports from other records at the Rota HANDAR and airport, DanDan and Merizo (Figure 3). The only complete wind trace that records the peak winds in the wall cloud and the relative calm within the eye was from the Kuentos Communications, Inc. in Maite (Figure 4). Relative to the lowest pressure which occurred at the CPA of Paka, we compared the strength and duration of the highest winds on either side. The wind from the southwest after the eye passage was more intense and of a longer duration. If this increase of 10 knots at Maite is applied to the Apra Harbor benchmark, a peak gust of 160 knots can be inferred.

Report of the Pacific Daily News

posted 2/13/98

"Meteorologists distill Paka data, put gusts at 173 mph" reads a headline from the February 9, 1998 edition of the Pacific Daily News. Writer Lalaine Estella reports that "after two month of studying denuded trees, aerial photographs of topless buildings, satellite pictures and Doppler radar and microwave images, island meteorologists have determined that Supertyphoon Paka blew gusts of 173 mph and dumped a billion gallons of water on the island."

"It was deginitely stronger than (Typhoon) Omar, but not as strong as (Typhoon) Pamela," said Charles Guard, a meteorologist with the Water and Energy Research Institute of the Western Pacific. Guard and other island weather experts presented their findings yesterday at a University of Guam seminar on Supertyphoon Paka.

Guard said it was difficult to determine exact wind speeds and rainfall immediately after the typhoon, because measurement devices had failed during the height of the storm. "Most anemometers on the island failed, except the one at the Port (Authority of Guam)," he said.

Final Statement from National Climate Extremes Committee

posted 03/11/98

A multi agency assessment team had concluded that a potential world record wind gust reported from Guam during the passage of Typhoon Paka in December 1997 is not a reliable report.

Typhoon Paka ravaged the island of Guam on 16 December, 1997, Andersen AFB, located on the north side of the island, reported a peak wind gust of 236 mph. If valid, this report would have exceeded the then current world record of 231mph for a measured wind speed recorded at Mt. Washington, NH in April 1934.

Following the passage of the typhoon, multi agency assessment teams, comprised of NOAA personnel from the Tropical Prediction Center, Operational Support Facility, and Pacific Region Headquarters, FEMA staff, and University researchers, visited the island to assess the data collected and warnings issued during the typhoon and to also assess the damage incurred. Their findings, after reviewing the wind record at the site, the Guam WSR88D radar data, a site survey and ground and aerial damage assessments, concluded that the peak gust report was unreliable. Through the Office of the Federal Coordinator for Meteorological Services, the U.S. Air Force evaluated the performance of the reporting anemometer and the Air Force concluded that the combination of high winds and heavy rain on the special "hot-wire" anemometer produced an unrealistically high wind speed. In addition, in their post-storm evaluation, the Joint Typhoon Warning Center, located on Guam and led by the U.S. Navy, reached a similar conclusion on the validity of the initial wind gust reported.

Based on the multiagency assessments, The National Climate Extremes Committee has determined that the reported wind gust from Typhoon Paka was not accurate and cannot be accepted as a world record wind speed.

Winds higher than the current world record of 231 mph have undoubtedly occurred during passage of the most extreme tropical systems and especially in tornadoes. However, reporting instrumentation have not survived to provide a documented record of these extremes.

This summary of the team and agency findings was issued by the National Climate Extremes Committee, established in 1997, and comprised of representatives from NOAA's National Climatic Data Center, National Weather Service, and the American Association of State Climatologists. The Committee's role is to serve as coordinator and final arbiter concerning national extremes of climatological data.

For information on the FMQ-13 hot-wire anemometer, see "What You Should Know About Wind and the AN/FMQ-13 Measuring Set", Flying Magazine, February 1997.

For information on the Number 2 Heated Anemometer, please see "World Record Wind: Measuring Gusts of 231 Miles an Hour" by Alexander A. McKenzie

For additional information about the1934 wind, please see the following reports published in the June 1934 issue of Monthly Weather Review:

"The Great Wind of April 11-12, 1934, on Mount Washington, N. H., and Its Measurement:

Part I - Winds of Superhurricane Force, and a Heated Anemometer for Their Measurement During Ice-Forming Conditions", by Salvatore Pagluica, pp. 186-189.

"Part II - The Mount Washington, N. H., Heated Anemometer", by D. W. Mann, pp. 189-191.

"Part III - The Calibration of the Mount Wahington, N. H., Heated Anemometer and the Analysis of Its Record of April 11-12, 1934", by Charles F. Marvin, pp. 191-195.