8. Super Typhoon DIANMU (Helen/09w) 
>> June 12-23, 2004
Dianmu: contributed by China, is the 'Mother of the Lightning', the goddess in charge of thunder and lightning.
Introduction
Dianmu was the third of five significant tropical cyclones during June and also the third super typhoon of the year. It formed in the vicinity of Yap, rapidly reaching a peak intensity of 155 kts before weakening and making landfall in Japan as a tropical storm. The following is a list of tropical cyclones that have reached 155 kts within the past ten years:
1995 - Angela (see note)
1997 - Keith
1998 - Zeb
2000 - Damrey
2001 - Faxai
Since 1990, only four storms have been stronger than 155 kts. They are: STYs Ivan & Joan (1997), STY Paka (1997), and STY Gay (1992). Super Typhoons that have reached 150 kts include Mike (1990), Yuri (1991), and Maemi (2003).
NOTE: There is strong reason to suspect that STY Angela was stronger than the current Best Track intensity of 155 kts. Dr. Karl Hoarau performed a detailed study of intense super typhoons of the post- reconnaissance era, and concluded that likely STY Gay of 1992 peaked at around 165 kts, and that Angela's peak was possibly near 170 kts. Karl's paper was presented at the AMS 26th Conference on Hurricanes and Tropical Meteorology at Miami in May, 2004. You can read the said paper here (in PDF format).
Storm Origins
At 0600 UTC on 11 June a new convective area developed and persisted within the monsoon trough approximately 340 nm east-southeast of Palau Island. It was added to JTWC's STWOs at this time, and the potential for development was given as poor. Animated multi-spectral imagery showed a possible LLCC with some deep convection. The suspect area was within a favourable environment of weak vertical wind shear and good diffluence. In the next regular STWO at 12/0600 UTC the potential was upped to fair. From there, the system proceeded to develop quickly, and a 12/2115 UTC SSM/I pass depicted spiraling rainbands curving into the centre. No TCFA was issued and JTWC released the first warning at 13/0000 UTC.
Synoptic History
At the time of the initial warning Tropical Depression 09W was located 100 nm south-southwest of Yap and moving slowly west-northwestward at 3 kts. Because of the threat to Yap and Palau, the National Weather Service in Guam began writing special advisories at 13/0328 UTC. TC-09W remained at depression status until 13/1800 UTC when it was upgraded to Tropical Storm Dianmu, JMA having raised their MSW to 40 kts (10-min avg). Both enhanced infrared and water vapor imagery indicated increasing poleward outflow thanks to an upper-level LOW to the north- east, and forecasts indicated that this would be enhanced further as a shortwave trough approached from the northwest.
By 14/0000 UTC JTWC had increased the MSW to 45 kts, and multi- spectral and QuikScat imagery both indicated that Tropical Storm Dianmu had consolidated to the southeast of the 13/1800 UTC warning position. Dianmu was essentially stationary approximately 100 nm west of Yap as it continued its strengthening phase, reaching typhoon intensity at 1800 UTC. At this time microwave imagery indicated that an eye could be forming, but this feature was not yet visible in infrared imagery. In addition to the poleward outflow, Dianmu had also acquired an excellent equatorward exhaust channel. The typhoon was centred just 85 nm north-northwest of Yap, the island lying within the zone of gale-force winds. Special advisories issued by the NWS mentioned that damaging winds were affecting Yap, but fortunately for the island community, Dianmu was beginning to move toward the north-northeast away from the island.
The 15th of June was a day of very significant intensification for Dianmu. At 0000 UTC it was a 70-kt typhoon located 110 nm north- northwest of Yap. The eye feature was still evident in microwave imagery but not in multi-spectral. By 15/1200 UTC the eye had appeared in satellite imagery as the MSW reached 120 kts. Moving north to north- northwest at speeds ranging from 6 to 9 kts, Dianmu strengthened into a super typhoon with a MSW of 145 kts by the time of the 1800 UTC warning. Enhanced infrared imagery revealed a symmetrical eye measuring 15 nm across. In addition, the typhoon exhibited excellent outflow in both poleward and equatorward directions.
At 16/0000 UTC Super Typhoon Dianmu, now with a MSW of 150 kts, was moving northward at 9 kts from a position approximately 300 nm north-northwest of Yap. The Prognostic Reasoning message issued at this time indicated that the northward heading would continue along the western periphery of the steering ridge located toward the northeast. The warning issued at 16/0000 UTC indicated the possibility of Dianmu strengthening to 160 kts in 12 hours. However, the peak intensity of Dianmu stopped 5 kts short of this value at 16/0600 UTC, the MSW remaining at 155 kts for the rest of the day. The wind radii were representative of an average-sized system and were as follows: winds of typhoon force extended 40 nm in all quadrants, the radius of 50-kt winds was 70 nm in all but the southeast quadrant (75 nm), and gale-force winds extended out 150 nm in the southeast quadrant and 140 nm elsewhere. (Super Typhoon Dianmu entered PAGASA's AOR on 16 June at about the time of its peak intensity, receiving the name Helen from that warning agency.)
At 0000 UTC on 17 June Super Typhoon Dianmu/Helen was centered 675 nm southeast of Okinawa, moving northwestward at 9 kts. The MSW began to fall off and enhanced infrared imagery indicated that the eye temperature had cooled. By 1200 UTC the intensity of Dianmu was hovering at 130 kts as the storm took a jog towards the west-northwest for the next twelve hours. When Dianmu fell below super typhoon strength at 17/1800 UTC its eye was cloud-filled and poleward diffluence had weakened significantly.
The next day Dianmu underwent a mini rejuvenation phase. This coincided with its northwestward passage over the slightly warmer Kuroshio Current. The typhoon was a 115-kt storm at 0000 UTC on 18 June approximately 520 nm south-southeast of Okinawa, and regained super typhoon intensity (MSW of 130 kts) at 18/1200 UTC. At this time, enhanced infrared and water vapor imagery showed a much improved poleward and equatorward diffluence pattern. Dianmu exhibited a 25-nm eye which began to warm. This indicated that the secondary peak had been reached and Dianmu was downgraded back to a 125-kt typhoon at 18/1800 UTC.
At 0000 UTC on 19 June Typhoon Dianmu was centred 255 nm south- southeast of Okinawa and was beginning its turn toward the north. At this time, multi-spectral satellite imagery showed a ragged, cloud-filled eye with the majority of the deep convection occurring in the southern quadrants. A "lane" was also evident in infrared satellite imagery as a result of dry air entrainment in the northwest quadrant. Weakening commenced during the day with the MSW dropping below 100 kts at 19/1800 UTC.
By 20/0000 UTC Typhoon Dianmu's radius of 50-kt winds were encroaching on Okinawa as the storm passed 75 nm to the east of the island. The weakening typhoon's outflow had diminished in all directions, deep convection had been eroded away in the western semi- circle, and the MSW had fallen to 80 kts. The system was beginning to interact with a trough located to the northwest of the system. Dianmu maintained typhoon-force winds until 20/1800 UTC when the intensity dropped below the typhoon threshold. At this time, the dying storm was located 175 nm south of Iwakuni, Japan.
Now that Dianmu was entering the baroclinic zone, the storm began to accelerate and rapidly take on extratropical characteristics. It made landfall near the city of Muroto on the island of Shikoku in southern Japan early on the 21st, crossed the main island of Honshu, from there moving into Hokkaido before heading out into the North Pacific as an extratropical system. JTWC issued their final warning at 21/1800 UTC, locating the center approximately 80 nm northwest of Misawa, Japan. The final JMA bulletin referencing ex-Dianmu placed a weakening 35-kt gale center in the Sea of Okhotsk east of Sakhalin Island at 1200 UTC on 23 June.
JMA's peak MSW (10-min avg) and minimum CP for Super Typhoon Dianmu/Helen were 100 kts and 915 mb, respectively. PAGASA's and NMCC's peak MSW estimates (10-min avg) were 105 kts and 130 kts, respectively.
Meteorological Observations
The following observations were sent by Huang Chunliang -- a special thanks to Chunliang for sending the data.
(1) Rainfall
(a) Falalop Island, Ulithi Atoll (WMO 91203, 10.0N/139.8E, 5 m) recorded 102.8 mm of rain from 12/0000 to 13/0000 UTC.
(b) Koror, Palau (WMO 91408, 7.3N/134.5E, 30 m) recorded 121.7 mm from 13/0000-14/0000 UTC, and 115.6 mm from 13/0600-14/0600 UTC.
(c) Owase, Japan (WMO 47663, 34.1N/136.2E, 27 m) measured a 24-hour accumulation of 207.5 mm from 21/0000 to 22/0000 UTC.
(2) Sustained Wind Observations
Station Prefecture WMO ID Lat/Lon Alt Dir Kts UTC --------------------------------------------------------------------- Minamidaitojima Okinawa 47945 25.8N/131.2E 15 SE 43 19/1630 " " " " " SSE 50 19/1830 " " " " " SSE 56 19/2130 Kitakaitojima * " ----- -----/------ -- SSE 49 19/1630 " " ----- -----/------ -- SSE 51 19/1920 " " ----- -----/------ -- S 54 19/2140 Naha " 47936 26.2N/127.7E 28 N 32 19/1620 Naha " " " " NNW 37 19/1920 Naha " " " " NNW 39 19/2020 Nago " 47940 26.6N/128.0E 6 NNE 32 19/1620 Fukuoka Fukuoka 47807 33.6N/130.4E 3 N 21 21/0200 Sasebo Nagasaki 47812 33.2N/129.7E 4 N 25 20/1850 Oita Oita 47815 33.2N/131.6E 5 SSE 22 20/0430 Hagi Yamaguchi 47754 34.4N/131.4E 6 S 21 19/2230 Saga Saga 47813 33.3N/130.3E 6 NE 23 20/1130 Asosan Kumamoto 47821 32.9N/131.1E 1142 ENE 25 20/2230 Nagoya Aichi 47636 35.2N/137.0E 51 SSE 31 21/0620 Gifu Gifu 47632 35.4N/136.8E 13 SSE 33 21/0620 Tsu Mie 47651 34.7N/136.5E 3 SE 50 21/0320 Omaezaki Shizuoka 47655 34.6N/138.2E 45 S 30 21/0640 " " " " " SSW 31 21/0840 Tsuruga Fukui 47631 35.7N/136.1E 2 SE 32 21/0250 Kanazawa Ishikawa 47605 36.6N/136.7E 6 WSW 26 21/1040 Niigata Niigata 47604 37.9N/139.1E 2 ESE 26 21/0840 Shirakawa Fukushima 47597 37.1N/140.2E 355 S 28 21/1110 " " " " " SSW 33 21/1450 Akita Akita 47582 39.7N/140.1E 6 ESE 24 21/1210 Sakata Yamagata ----- 38.9N/139.9E 3 ESE 25 21/1050 " " ----- " " ESE 24 21/1210 Ishinomaki Miyazaki 47592 -----/------ 43 SE 37 21/1300 " " " -----/------ " SE 39 21/1340 Morioka Iwate 47584 39.7N/141.2E 155 S 24 21/1750 Hachinohe Aomori 47581 40.5N/141.5E 27 SE 27 21/1420 * - Kitadaitojima is the neighboring island northeast of Minamidaitojima
(3) Wind Gust Observations
Station Prefecture WMO ID Lat/Lon Alt Dir Kts UTC ---------------------------------------------------------------------- Minamidaitojima Okinawa 47945 25.8N/131.2E 15 SE 60 19/1009 " " " " " SE 71 19/1350 " " " " " SE 75 19/1542 " " " " " SSE 87 19/1750 " " " " " SSE 95 19/2120 Naha " 47936 26.2N/127.7E 28 N 53 19/1624 Naha " " " " N 59 19/1729 Naha " " " " NNW 61 19/2203 Nago " 47940 26.6N/128.0E 6 NNE 59 19/1550 Nago " " " " N 61 19/1959 Okinoerabu Kagoshima 47942 27.4N/128.7E 27 NE 57 19/1947 Naze Kagoshima 47909 28.4N/129.5E 3 N 61 20/0115 Shimizu Kochi 47898 32.7N/133.0E 31 E 70 20/1950 Murotomisaki Kochi 47899 33.3N/134.2E 185 ESE 78 20/1832 " " " " " ESE 100 20/2219 " " " " " SE 108 20/2240 " " " " " SE 111 unknown Fukuoka Fukuoka 47807 33.6N/130.4E 3 N 39 21/0156 Izuhara Nagasaki 47800 34.2N/129.3E 4 NW 44 21/0058 Oita Oita 47815 33.2N/131.6E 5 SE 36 20/0248 Hagi Yamaguchi 47754 34.4N/131.4E 6 S 41 20/0457 Saga Saga 47813 33.3N/130.3E 6 N 33 20/2234 Asosan Kumamoto 47821 32.9N/131.1E 1142 ENE 66 20/2217 Uwajima Ehime 47892 33.2N/132.6E 2 NNE 49 20/1600 Nagoya Aichi 47636 35.2N/137.0E 51 SSE 65 21/0619 Gifu Gifu 47632 35.4N/136.8E 13 SE 65 21/0548 Tsu Mie 47651 34.7N/136.5E 3 ESE 67 21/0314 Omaezaki Shizuoka 47655 34.6N/138.2E 45 S 52 21/0638 " " " " " S 54 21/0711 Tsuruga Fukui 47631 35.7N/136.1E 2 ESE 77 21/0248 Kanazawa Ishikawa 47605 36.6N/136.7E 6 SSW 29 21/0951 Niigata Niigata 47604 37.9N/139.1E 2 E 42 21/0839 Shirakawa Fukushima 47597 37.1N/140.2E 355 S 52 21/1236 " " " " " S 57 21/1456 Akita Akita 47582 39.7N/140.1E 6 ESE 45 21/1238 Sakata Yamagata ----- 38.9N/139.9E 3 ESE 42 21/1102 " " ----- " " ESE 45 21/1238 Ishinomaki Miyazaki 47592 -----/------ 43 SE 57 21/1257 Morioka Iwate 47584 39.7N/141.2E 155 S 39 21/1735 Hachinohe Aomori 47581 40.5N/141.5E 27 ESE 53 21/1419
Damage and Casualties
At the time of this writing three people are known to have been killed with three persons reported missing as a result of Typhoon Dianmu's passage across Japan. Airline services and rail transport were disrupted, and the typhoon forced nine oil refineries to temporarily halt operations. Damage due to the storm appears to have been minimal.
(Report written by Kevin Boyle with significant contributions by Huang Chunliang)
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