Marine Weather Review—North Pacific Area
May through August 2006

By George P. Bancroft, NOAA National Center for Environmental Prediction

Introduction

The weather pattern over the North Pacific remained rather active from May into early June when most of the cyclonic systems strong enough to produce storm-force winds occurred. There was a hurricane-force storm in the western Pacific east of Japan in early June, a very unseasonable event that stood out as the most significant non-tropical event of the period. From the middle of June through August OPC analyzed no non-tropical storm-force lows, a period that normally has declining activity going into mid-summer. Cyclonic activity usually picks up in August, but this year August was without any storm-force lows.

Tropical activity in the western Pacific was concentrated in the month of August, during which five named tropical cyclones appeared on OPC’s oceanic analysis charts used for radiofacsimile transmission. These headed in the direction of Japan and either passed south of Japan or turned north and weakened near Japan or the Kurile Islands. Three tropical cyclones were typhoons, including Super Typhoon Ioke which came from the central Pacific at the end of August. No tropical systems redeveloped into intense lows after becoming extratropical during this period.

Tropical Activity

Typhoon Maria: Tropical Storm Maria formed near 26N 145E at 1200 UTC August 5 with 35 kts maximum sustained winds. Six hours later the Maersk Wind (S6TY) near 27N 143E reported east winds of 50 kts. The cyclone intensified while tracking northwest, briefly becoming a typhoon near 31N 137E, south of Japan, at 1200 UTC August 7 with maximum sustained winds of 65 kts with gusts to 80 kts. Maria then weakened while turning to the north and then northeast, becoming a tropical storm with maximum sustained winds 45 kts with gusts to 55 kts while passing near 34N 137E at 1200 UTC on the 8th. The ship British Confidence (MLJA8) (33N 138E) just southeast of the center encountered south winds of 50 kts at that time. Maria then became an extratropical gale 35N 141E with a 1000 hPa central pressure, just east of Tokyo, at 0000 UTC August 9. Maria’s extratropical remains then moved northeast, before turning north along 150E and weakening near the Kurile islands on the 13th.

Typhoon Saomai:Figure 1 shows Typhoon Saomai just entering OPC’s oceanic chart area at 1200 UTC August 6, along with Tropical Storm Maria to the north. Saomai had just been upgraded to a typhoon by Joint Typhoon Warning Center near Honolulu. Saomai then moved to near 18N 139E with maximum sustained winds 75 kts with gusts to 90 kts twelve hours later, and maintained this intensity until the cyclone passed west of the area about 250 nmi south of Japan late on the 7th, where further intensification occurred.

North Pacific Surface Analysis charts

Figure 1. OPC North Pacific Surface Analysis chart (Part 2 - west) valid 1200 UTC August 6, 2006.

Tropical Storm Wukong: Tropical Depression 11W formed southeast of Japan near 22N 141E at 1200 UTC August 12 and, like its predecessors moved northwest initially. Maximum sustained winds were initially 25 kts with gusts to 35 kts. The cyclone intensified to a tropical storm near 25N 139E at 0000 UTC on the 13th, with the Japanese Meteorological Agency naming it Wukong six hours later. Maximum sustained winds were 35 kts with gusts to 45 kts. The ship (name unknown) (ZOYC5) (29N 139E) reported east winds of 35 kts at 1200 UTC August 13. Wukong slowly intensified while turning toward the north, attaining maximum strength near 27N 138E at 1800 UTC on the 14th with sustained winds to 50 kts and gusts to 65 kts. The cyclone then turned to the northwest and then west, passing west of the area about 300 nmi south of Japan on August 16, where it slowly weakened.

Tropical Storm Sonamu: While Wukong was about 400 nmi south of Japan, Tropical Storm Sonamu moved northeast into OPC’s oceanic map area near 21N 136E by 0000 UTC August 15 with maximum sustained winds of 45 kts with gusts to 55 kts. The cyclone weakened to a tropical depression while passing near 26N 140E eighteen hours later, before dissipating 250 nmi south of Tokyo late on August 15.

Super Typhoon Ioke: Ioke was formerly Hurricane Ioke in the central Pacific up until early on August 27 when it crossed 180W and the Joint Typhoon Warning Center named it Super Typhoon Ioke, a special warning classification for storms with maximum sustained winds 130 kt or higher. At 1200 UTC August 27 Ioke was at maximum strength, located near 17N 179E with maximum sustained winds of 140 kts with gusts to 170 kts. This intensity would rate as Category 5, highest on the Saffir-Simpson intensity scale (See Reference 1). Ioke then tracked west between 16N and 17N until beginning a turn toward the northwest and crossing 170E early on the 30th. At the end of August Ioke passed near 20N 165E, still a super typhoon with maximum sustained winds of 135 kts and gusts to 165 kts. Ioke’s long history continued into September and more information on this storm will be found in the next issue of Mariners Weather Log.

Other Significant Events

North Pacific Storm, May 1-3: The relatively active month of May began with a storm center moving along 40N and approaching the dateline as shown in Figure 2. The cyclone moved east and weakened to a gale at 0000 UTC May 2, before turning northeast and re-intensifying into a storm-force low as shown in the second part of Figure 2, with the cyclone at maximum intensity in terms of central pressure. As for winds with this system, high-resolution QuikScat satellite-derived winds with this system were actually a little higher when the center was near or south of 40N, with Figure 3 revealing a swath of north winds of 50 to 55 kts on the back side of the storm center. The time of this image is less than 5 hours earlier than the chart time of the first part of Figure 2. Ship reports were sparse, not exceeding 35 kts. The cyclone then weakened while continuing to move northeast, dissipating near the south coast of mainland Alaska late on May 4.

North Pacific Surface Analysis charts

Figure 2. OPC North Pacific Surface Analysis charts valid 1200 UTC May 1 (Part 2 - west) and 1200 UTC May 3
(Part 1-east), 2006.

High resolution QuikScat scatterometer

Figure 3. High-resolution QuikScat scatterometer image of satellite-sensed winds around the storm shown in the first part of Figure 2, valid at 0721 UTC May 1, 2006, or less than five hours prior to the valid time of the first part of Figure 2. The resolution is 12.5 km, versus 25 km in the coarser version of the imagery. The center of the storm appears near 39N 173E.
Image is courtesy of NOAA/NESDIS /Office of Research and Applications.

North Pacific Storm, May 3-19: As depicted in Figure 4, a complex system with several centers scattered between 30N and 52N consolidated into a single 978 hPa cyclone in the twenty-four hour period ending at 1800 UTC on the 3rd , when much of the intensification occurred. At 0000 UTC on the 4th, the APL Korea (WCX8883) near 51N 168E reported east winds of 55 kts north of the center. Six hours later the Newport Bay (MQEC7) encountered west winds of 45 kts near 44N 174E. The cyclone developed a lowest central pressure of 970 hPa near 51N 180W at 1800 UTC May 4, the lowest pressure attained by a non-tropical system in the North Pacific during the four-month period. The storm system subsequently re-formed to the northeast and weakened to a gale near the Alaska Peninsula early on the 5th, before dissipating in the northern Gulf of Alaska late on May 7.

North Pacific Surface Analysis charts

Figure 4. OPC North Pacific Surface Analysis charts (Part 2) valid 1800 UTC May 2 and 3, 2006.

Northwest Pacific and Bering Sea Storm, May 14-15: A developing storm tracked northeast into the western Bering Sea as depicted in the two parts of Figure 5. The system developed storm force winds by 1800 UTC May 14, which continued until the cyclone weakened in the northwest Bering Sea late on the 15th. The ship Vincent Thomas Bridge (H3WJ) (44N 159E) reported southwest winds of 45 kts at 1800 UTC on the 14th, the highest wind from conventional observations. A high-resolution scatterometer pass (Figure 6) reveals winds as high as 55 kts in westerly flow south of the storm center, and southeast winds as high as 50 kts in the southern Bering Sea associated with the front. The second part of Figure 5 shows the storm at maximum intensity. The cyclone then weakened slowly while drifting through the northern Bering Sea from late on the 15th through the 18th, before dissipating on May 19.

North Pacific Surface Analysis charts

Figure 5. OPC North Pacific Surface Analysis charts (Part 2) valid 0000 UTC May 14 and 1200 UTC May 15, 2006.

High resolution QuikScat scatterometer

Figure 6. High-resolution QuikScat scatterometer image of satellite-sensed winds around the eastern side of the storm shown in Figure 5. The valid time of the pass is 0753 UTC May 15, 2006, or about four hours prior to the valid time of the second part of Figure 5. The center of the storm is apparent near the left edge of the image, near 53N 165E.
Image is courtesy of NOAA/NESDIS/ Office of Research and Applications.


Eastern North Pacific Storm of May 14-15: Concurrent with the northwestern Pacific development described above, a slow-moving relatively compact storm system developed from a frontal wave of low pressure relatively far south in the eastern Pacific, west of California, as depicted in Figure 7. The initial intensification was impressive, with the central pressure dropping 14 hPa to 1000 hPa in the six-hour period ending at 1200 UTC May 14. The second part of Figure 7 shows the cyclone near maximum intensity. The World Spirit (ELWG7) reported southwest winds of 50 kts south of the center at 1200 UTC on the 15th and is plotted in Figure 7. The cyclone developed a lowest central pressure of 984 hPa near 42N 142W twelve hours later, but by then the circulation expanded and winds weakened to gale force. The system subsequently weakened slowly while drifting north through the 17th, before stalling off Southeast Alaska on May 18 and dissipating the next day.

High resolution QuikScat scatterometer

Figure 7. OPC North Pacific Surface Analysis charts (Part 1) valid 0000 UTC May 14 and 1200 UTC May 15, 2006.

Western North Pacific Storm, June 7-8: Figure 8 shows the initial development of this unseasonably intense storm over a thirty-six hour period ending at 1200 UTC June 8, the time of the second part of Figure 8. The central pressure fell 11 hPa in the twelve-hour period prior to reaching maximum intensity, 975 hPa. Figure 9 is a high-resolution QuikScat pass showing winds to 70 kts on the south side of the storm center, over relatively warm water. The author cannot recall seeing hurricane-force winds in a non-tropical cyclone (without tropical origin) in the North Pacific in summer since OPC started using scatterometer winds in the late 1990s. Available conventional observations were sparse, with the United Spirit (ELYB2) reporting the strongest wind at 45 kts, from the northwest, near 40N 161E at 0000 UTC June 9. The same ship also reported seas of 11.0 m (36 ft). The cyclone subsequently weakened rapidly on June 8, and then more slowly afterwards, while moving east-northeast with winds lowering to gale force by early on the 9th. The cyclone then turned more north toward the eastern Aleutians on June 10 and dissipated over southwestern Alaska on the 12th.

High resolution QuikScat scatterometer

Figure 8. OPC North Pacific Surface Analysis charts (Part 2) valid 0000 UTC June 7 and 1200 UTC June 8, 2006.

High resolution QuikScat scatterometer

Figure 9. High-resolution QuikScat scatterometer image of satellite-sensed winds around the south and southwest sides of the storm shown in the second part of Figure 8. The valid time of the pass is 0737 UTC June 8, 2006, or about four and one-half hours prior to the valid time of the second part of Figure 8. The center of the storm is apparent in the upper right portion of the figure near 40N 161E.
Image is courtesy of NOAA/NESDIS/ Office of Research and Applications

References

1. From Tropical Prediction Center website, http://www.nhc.noaa.gov/aboutsshs.shtml.

2. Sienkiewicz, J. and Chesneau, L., Mariner’s Guide to the 500-Mb Chart (Mariners Weather Log, Winter 1995).