Marine Weather Review – North Pacific Area May to August 2009

By George P. Bancroft
NOAA National Center for Environmental Prediction

Introduction

The period of May to August includes the late spring and summer months, a time of weaker cyclonic activity. For the North Pacific 2009 was no exception, with May being most active with five low pressure areas of non tropical origin producing winds of at least storm force, while June and July brought declining activity leading to a July with no low pressure systems with winds exceeding gale force (higher than 47 kts). Activity picked up abruptly late in August as four strong cyclones developed storm force or higher winds as they tracked east and northeast toward the northeastern Pacific waters. One of these had tropical origin as Typhoon Vamco and briefly developed hurricane force winds after transition to an extratropical (outside the tropics with fronts) cyclone.

Five western Pacific tropical cyclones affected OPC’s ocean basin radiofacsimile chart area during the period, with major Typhoon Kujira occurring early in May, followed by a lengthy quiet period until Tropical Storms Morakot and Etau developed south of Japan early in August, followed by Typhoon Vamco in mid August and Tropical Storm Krovanh at the end of the month. A rare eastern Pacific tropical cyclone, Guillermo, moved into the central Pacific north of Hawaii and entered OPC’s high seas area of responsibility north of 30N during the third week in August as a weakening tropical storm.

Tropical Activity

Typhoon Kujira: Kujira followed a northeastward track into OPC’s oceanic radiofacsimile chart area about 900 nmi south of Japan early on May 5 with maximum sustained winds of 100 kts with gusts to 125 kts. This is equivalent to a major (Category 3) hurricane on the Saffir-Simpson Scale (Reference 1). The cyclone weakened rapidly beginning early on the 6th with its winds dropping to tropical storm strength by 0000 UTC on the 7th. Kujira degenerated to an extratropical gale with 1003 hPa central pressure six hours later, after which it moved slowly northeast to near 46N 166E three days later. The remains of Kujira then turned southeast on the 10th, blocked by high pressure over the Bering Sea, and then dissipated well south of the central Aleutians on May 13.

Tropical Storm Morakot: Tropical Storm Morakot formed near 21N 136E well south of Japan at 1800 UTC August 3 with maximum sustained winds 35 kts with gusts to 50 kts. The cyclone moved slowly northwest with slow intensification, reaching 23N 132E thirty six hours later with maximum sustained winds of 55 kts with gusts to 70 kts. This motion continued as Morakot moved west of the area.

Tropical Storm Etau: Tropical Depression 10W formed in OPC’s radiofacsimile chart area near 24N 140E at 0000 UTC August 8 and moved northwest, with maximum sustained winds of 30 kts with gusts to 40 kts, and became Tropical Storm Etau near 30N 135E by 1800 UTC on the 9th as its winds increased by 5 kts. The cyclone then turned northeast by the 10th and more eastward the next day, before becoming an extratropical gale with the central pressure as low as 992 hPa near 34N 152E by 1800 UTC on the 12th. A vessel with the SHIP identifier near 30N 132E reported north winds of 40 kts at 1200 UTC on the 10th. The ship MGGF9 (33N 141E) reported west winds of 45 kts and 5.5 m seas (18 ft). Extratropical Etau then weakened while tracking northeast to the southern Gulf of Alaska on the 17th where it dissipated.

Typhoon Vamco: An intensifying Tropical Storm Vamco moved north into OPC’s North Pacific chart area near 17N 157E by 1800 UTC August 18 and strengthened into a typhoon six hours later, with maximum sustained winds of 65 kts with gusts to 80 kts. Vamco attained a peak intensity near 21N 157E at 0600 UTC August 21 with maximum sustained winds of 115 kts with gusts to 140 kts. This intensity is equivalent to Category 4 on the Saffir-Simpson intensity scale (Reference 1). The cyclone then began a weakening trend while gradually turning more to the northeast, with its winds lowering to minimal typhoon strength as the center passed near 42N 159E at 0600 UTC on the 25th. Figure 1 shows Typhoon Vamco transitioning into an extratropical hurricane force low over a twelve hour period ending at 1200 UTC on the 25th, merging with a frontal zone in the process. The high resolution QuikSCAT image (Figure 2) of the winds around Vamco less than four hours prior to the valid time of the second part of Figure 1 reveals a compact circulation of strongest winds close to the center, a feature of tropical cyclones. The strongest winds, of up to 70 kts, are to the right of the storm track, a common feature of tropical systems entering the mid-latitude westerlies. Extratropial Vamco then entered the southern Bering Sea early on the 26th as a storm force low and turned east. Figure 14 shows the cyclone over the eastern Aleutian Islands and re-entering the North Pacific. The APL Philippines (WCX8884) near 54N 178W reported north winds of 40 kts and 9.5 m seas (31 ft). At 1800 UTC that day the vessel WCZ6534 (54N 167W) encountered northeast winds of 45 kts, and twelve hours later the ship 3FZA9 (54N 165W reported north winds of 50 kts and 4.5 m seas (15 ft). Among buoys, 46073 (55.0N 172.1W) reported the highest wind with north winds to 45 kts along with seas of 4.5 m (14 ft) at 0900 UTC on August 27. Buoy 46035 (57.1N 177.8W) reported a northeast wind of 40 kts and 4.0 m seas (13 ft) at 1500 UTC on the 26th and highest significant wave heights of 6.0 m (19 ft) seven hours later. The cyclone subsequently moved southeast with slow weakening to a gale force low over the next twenty-four hours before turning northeast and weakening to a sub gale force low in the Gulf of Alaska on the 29th and finally turning southeast and dissipating west of Vancouver Island at the end of the month.

Tropical Storm Krovanh: Krovanh began as Tropical Depression 12W near 22N 148E at 0000 UTC August 28 with maximum sustained winds of 30 kts with gusts to 40 kts. The cyclone was upgraded by the Joint Typhoon Warning Center to a tropical storm six hours later, with the storm moving northwest and reaching a peak intensity of 60 kts sustained winds with gusts to 75 kts near 30N 144E at 1800 UTC August 29. Krovanh then began to recurve to the north and then northeast on the 30th with some weakening. By 1200 UTC on the 30th the cyclone was near 32N 140E with maximum sustained winds of 55 kts with gusts to 70 kts. The cyclone maintained this intensity as it moved to 39N 144E by month’s end. The APL Philippines (WCX8884) near 35N 145E reported southeast winds of 35 kts and 8.0 m seas (26 ft) at 0600 UTC on August 31. The drifting buoy 41591 (35.3N 143.8E) at 1800 UTC reported southeast winds of 45 kts. Tropical Storm Krovanh continued on a northeastward track into early September as an extratropical low and will be covered in the April 2010 issue of Mariner’s Weather Log.

Tropical Storm Guillermo: Guillermo was a tropical eastern Pacific system that moved northwest into OPC’s area of responsibility for high seas text warnings and forecasts north of 30N, north of Hawaii, early on August 19 (Figure 13). This is a rare occurrence, as tropical cyclones coming out of the eastern Pacific on a northwestward track tend to die over cool ocean waters. It was a minimal tropical storm with maximum sustained winds of 35 kts with gusts to 45 kts. Guillermo quickly degenerated to a tropical depression six hours later and to a remnant low by 0600 UTC on the 20th near 32N 158W. Dissipation occurred on the 22nd near 40N 154W.

Other Significant Events

North Pacific Storm, May 3-4: Figures 3 and 4 show a slow moving frontal low pressure wave that developed at subtropical latitudes south of a strong high pressure area covering much the western North Pacific. Figure 3 shows it near maximum intensity with the “STORM” label, which is supported by the appearance of gale to storm force winds from the east and northeast in the upper part of the QuikSCAT image of Figure 5. The author suspects that the gale force west winds bordering on the east winds across the upper part of the image have rain contamination and are unreliable (Reference 5). Another scatterometer pass from earlier that day also showed storm force winds. Winds lowered to gale force by the 5th (Figure 4) as the cyclone began to drift northwest and weaken, with dissipation following on the 8th.

Northeast Pacific Storm, May 4-5: The development of this cyclone is depicted in Figures 3 and 4. It originated from a frontal wave of low pressure near 34N 171W at 0600 UTC May 3 and appears in Figure 3 as a secondary development on a front while the primary low near 50N 143W remained nearly stationary. The central pressure fell 18 hPa in the twenty four hour period ending at 0000 UTC on the 5th. Figure 4 shows the cyclone at its peak intensity (976 hPa) among six hourly OPC surface analysis charts, but the ship report of 974 hPa in Table 1 if accurate would support this cyclone as the deepest of the period in the North Pacific. The storm was short lived, as it quickly moved inland and dissipated later that day. Table 1 lists the most notable ship and coastal station observations taken in this storm.

North Pacific Storm, May 10-12: A gale force low dropped southeast to the Bering Sea on May 5th and 6th, weakened south of the central Aleutians on May 7 and then drifted east with Figure 6 depicting its re-intensification south of a strong blocking high over the eastern Bering Sea. The strongest winds were in the easterly flow between the low and front and the high to the north as revealed in the high resolution QuikSCAT data of Figure 7. In the west there is even an 80 kts wind retrieval and the winds in the area are rain flagged; however, rain has less effect on higher wind speeds (Reference 5). The hurricane force east winds in the western side of the image may need to be adjusted down due to rain contamination but it may not be enough to rule out hurricane force wind speeds. The cyclone later became a complex gale force system on the 12th before redeveloping east toward the coast and entering the Pacific Northwest states on the 13th.

Table 1. Ship and coastal C/MAN observations taken during the passage of the northeastern Pacific storm of May 4-5, 2009.
Observation Position Date/Time (UTC) Wind Seas (m/ft)
WABS 41N 126W 04/1500 SE 40 6.5/21
Bonn Express (DGNB) 41N 132W 04/1800 SW 45 5.0/16
WSLH 42N 125W 04/1800 SE 45 4.0/13
WDB9918 42N 126W 04/1900 S 45 6.5/21
PHSG 46N 125W 04/2200 E 40 2.5/9
05/0000 5.0/17
A8LG9 49N 129W 05/0300 E 60 8.5/28
48N 129W 05/0600 SW 50 9.0/30
05/0600 (Pressure 974.0)
47N 128W 05/1000 SW 45 8.5/28
Tatoosh Island (TTIW1) 48.4N 124.8W 05/1300 S 50

Northwestern Pacific Storm, May 17-18: This storm developed quickly after emerging off the coast of Asia late on May 16. Figure 8 shows the subsequent development of this system over a twenty four hour period leading to the 974 hPa cyclone at peak intensity in the second part of the figure. Along with perhaps the northeastern cyclone of May 4-5 this was the most intense low of the period in the North Pacific in terms of central pressure. The Great Land (WFDP) at 1800 UTC on the 17th reported south winds of 50 kts near 36N 144E. Six hours later the Bonn Express (DGNB) encountered southeast winds of 45 kts near 44N 151E while LADQ4 (46N 152E) reported southeast winds of 35 kts and 8.0 m seas (26 ft). The cyclone subsequently moved northeast and weakened to a gale early on May 18 and a sub gale low on the 19th. The system later re-formed in the central Bering Sea on the 21st and then moved east-southeast and dissipated over Southeast Alaska on May 26.

Figure 1 Part 1     Figure 1 Part 2

Figure 1. OPC North Pacific Surface Analysis charts (Part 2 - west) valid 0000 UTC and 1200 UTC August 25, 2009.

Western North Pacific Storm of May 27-28: Another slow moving frontal wave of low pressure formed at relatively far southern latitudes with strong high pressure to the north. This was similar to the May 3-4 event farther east with storm force east winds on the north side, which lasted about twenty-four hours before the system moved northeast and weakened over Japan on May 30.

Central North Pacific Storms, June 14-16: The 979 hPa storm center near the Aleutians in Figure 9 from the merging of two systems, one a gale force low moving northeast from south of Japan and an old low near the Aleutians. The other near 43n160w developed from a frontal wave along the west to east front near 30N. The ship DQVJ (40N 168W) at 1200 UTC on the 14th and again near 40N 159W at 0600 UTC on the 15th reported west winds of 55 kts. A vessel with the SHIP callsign reported west winds of 35 kts and 8.0 m seas (26 ft) at 1800 UTC June 15. High resolution QuikSCAT passes valid at 0538 UTC and 0719 UTC June 15 (around the valid time of Figure 9) showed 50 kts wind retrievals northeast of the eastern low center and on the southwest side of the western low. The two lows subsequently merged into one gale center just south of the Alaska Peninsula early on the 17th before drifting northeast and dissipating over Southeast Alaska by the 20th.

Northeastern Pacific Storm of June 23-24: Figure 10 depicts the development of the 1009 hPa low pressure wave near 165W into a storm over a thirty-six hour period. A high resolution scatterometer image close to the valid time of the second part of Figure 10 (Figure 11) reveals the highest winds on the southwest or cold air side of the low of up to 55 kts, unseasonably strong for a late June cyclone. The Cho Yang Ark (DQVJ) near 45N 138W encountered northwest winds of 45 kts at 1200 UTC June 24. The vessel DMPX (48N 136W) reported northwest winds of 40 kts and 6.5 m seas (22 ft) six hours later. The buoy 46036 (48.4N 133.9W) reported northwest winds of 31 kts with gusts to 41 kts and 3.0 m seas (10 ft) at 1700 UTC on the 24th followed twelve hours later by a report of seas as high as 5.5 m (18 ft). The cyclone moved onshore on the British Columbia coast as a gale late on the 24th then weakened inland.

Northeastern Pacific Storm of June 26-27: The next developing storm over the northeastern waters originated as a low pressure wave with a 1016 hPa central pressure near 41N 163W at 1800 UTC June 25 with the period of most rapid intensification occurring in the twenty-four hour period covered by Figure 12, when the pressure fell 26 hPa. The second part of Figure 12 shows the cyclone at peak intensity. The OOCL Japan (VRWB7) reported west winds of 40 kts and 9.0 m seas (30 ft) at 0000 UTC June 27. Seven hours later the ship PHEO encountered southeast winds of 55 kts near 55N 131W. The vessel WDD2074 (52N 141W) reported southwest winds of 35 kts and 9.5 m seas (31 ft) at 0500 UTC on the 27th. The Westerdam (PINX) at 1000 UTC on the 27th encountered south winds of 45 kts near 52N 129W. Tracking north of its predecessor, this strong system weakened to a gale on the 27th before passing inland over Southeast Alaska on the 28th.

Figure 2

High resolution QuikSCAT scatterometer image of satellite sensed winds around the extratropical hurricane force low, former Typhoon Vamco, shown in the second part of Figure 1. The resolution is 12.5 km, versus 25 km in the coarser resolution version of QuikSCAT imagery. The valid time of the pass is 0818 UTC August 25, 2009, or about three and three-quarters hours prior to the valid time of the second part of Figure 1. Image is courtesy of NOAA/NESDIS/ Office of Research and Applications.

Northeast Pacific Storm, August 23-24: A 1014 hPa frontal wave of low pressure near 50N 158W at 0000 UTC August 23 moved east-northeast and rapidly intensified, with the central pressure falling 24 hPa, leading to a storm force low near 51N 145w with a 990 hPa central pressure at 0000 UTC on the 24th. The center developed a lowest pressure of 985 hPa six hours later as it turned more northeast. The strongest winds were on the south and southwest sides of the center in QuikSCAT imagery near the time of maximum intensity, up to 55 kts, similar to Figure 11 for the June 23-24 event. The Horizon Tacoma (KGTY) near 52N 144W at 1200 UTC on the 24th encountered northwest winds of 45 kts. A drifting buoy at 50.1N 144.7W (48400) reported northwest winds of 40 kts at 0500 UTC August 24. The first part of Figure 14 shows the cyclone weakening in the Gulf of Alaska.

Northeast Pacific Storm, August 26-27: This cyclone had origins in the northwestern Pacific, as stalled low pressure in the Sea of Okhotsk on the 22nd and 23rd of August redeveloped in the western Bering Sea late on the 23rd as a gale. The system moved east and then southeast across the eastern Aleutian Islands late on the 24th. Figure 14 shows the subsequent re-intensification of this system in the southeast Gulf of Alaska. It briefly developed storm force winds on the northeast side and was similar to the late June event. The ship WJBU (50N 132W) reported southeast winds of 45 kts and 5.0 m seas (16 ft). The Lykes Discoverer (A8GS3) near 51N 137W encountered east-southeast winds of 45 kts and 7.0 m seas (23 ft). Buoy 46036 (48.5N 134.0W) at 0400 UTC on the 27th reported southeast winds of 35 kts and 7.5 m seas (25 ft). The cyclone then turned northwest and weakened near Kodiak Island on the 28th and became absorbed by the remains of Typhoon Vamco shortly thereafter.

Figure 3 Part 1     Figure 3 Part 2

Figure 3. OPC North Pacific Surface Analysis charts (Parts 2 – west and 1 – east) valid 1200 UTC May 4, 2009.

Figure 4 Part 1     Figure 4 Part 2

Figure 4. OPC North Pacific Surface Analysis charts (Parts 2 – west and 1 – east) valid 0600 UTC May 5, 2009.

Figure 5

Figure 5. High resolution QuikSCAT scatterometer image of satellite sensed winds around the storm centered south of 30N shown in the first part of Figure 3. The valid time of the pass is 1828 UTC May 4, 2009, or about six and one-half hours later than the valid time of Figure 3. The center of the storm is in the area of lighter winds near 26N 168E. The author believes that the swath of west winds between the center and the east winds to the north has erroneous directions. Image is courtesy of NOAA/NESDIS/ Office of Research and Applications.

Figure 6 Part 1     Figure 6 Part 2

Figure 6. OPC North Pacific Surface Analysis charts valid 1200 UTC May 9 (Part 2) and 1200 UTC May 11, 2009 (Part 1).

Figure 7

Figure 7 High resolution QuikSCAT scatterometer image of satellite sensed winds around the east side of the storm shown in the second part of Figure 6. The valid time of the pass is 0546 UTC May 11, 2009, or about six and one-quarter hours prior to the valid time of the second part of Figure 6. The center of the storm is just off the lower left edge of the image with the stronger winds found to the north and northeast. Image is courtesy of NOAA/NESDIS/ Office of Research and Applications.

Figure 8 Part 1     Figure 8 Part 2

Figure 8. OPC North Pacific Surface Analysis charts (Part 2) valid 0600 UTC May 17 and 18, 2009.

Figure 9 Part 1     Figure 9 Part 2

Figure 9. OPC North Pacific Surface Analysis charts (Parts 2 – west and 1 - east) valid 0600 UTC June 15, 2009.

Figure 10 Part 1     Figure 10 Part 2

Figure 10. OPC North Pacific Surface Analysis charts (Part 1) valid 1800 UTC June 22 and 0600 UTC June 24, 2009.

Figure 11

Figure 11. High resolution QuikSCAT scatterometer image of satellite sensed winds around mainly the south semicircle of the storm shown in the second part of Figure 10. The valid time of the pass is about 0324 UTC June 24, 2009, or about two and one-half hours prior to the valid time of the second part of Figure 10. The center of the storm is near 49N 140W near the top of the image. Image is courtesy of NOAA/NESDIS/ Office of Research and Applications.

Figure 12 Part 1     Figure 12 Part 2

Figure 12. OPC North Pacific Surface Analysis charts (Part 1) valid 0600 UTC June 26 and 26, 2009.

Figure 13 Part 1     Figure 13 Part 2

Figure 13. OPC North Pacific Surface Analysis charts (Part 1) valid 0600 UTC August 19 and 20, 2009.

Figure 14 Part 1     Figure 14 Part 2

Figure 14. OPC North Pacific Surface Analysis charts (Part 1) valid 1200 UTC August 25 and 27, 2009.

Back to top