20. Typhoon NOCK-TEN (Tonyo/28w)           Print this Article
>> October 14-27, 2004

Nock-ten: contributed by Laos, is the name of a type of bird.

Storm Origins

Typhoon Nock-ten originated from a disturbance that formed amongst the Marshall Islands, and was first mentioned in a STWO at 1730 UTC 12 October when it was located approximately 45 nm west of Kwajalein Atoll. Initially described as a 'poor' development area, the potential for tropical cyclone formation was raised to 'good' at 13/1430 UTC and a TCFA issued. The first warning was published on Tropical Depression 28W at 14/0000 UTC, which was centred at that time 275 nm east-northeast of Pohnpei and moving westward along the southern periphery of the mid-level steering ridge situated to the northeast. TD-28W exhibited little change over the next couple of days, and apart from a slight increase in intensity to 30 kts, there was little else to report. The system tracked generally west-northwestward, then turned towards the northwest early on the 15th. The storm then decelerated to a slow westward drift at 15/1800 UTC when it was relocated to a position 255 nm north-northeast of Pohnpei. The reason for TD-28's lack of development was its proximity to an unfavourably-placed upper-level LOW which was located to its west.

Synoptic History

Tropical Depression 28W was still looking rather disorganised early on the 16th. At 0000 UTC the poorly-defined centre was readjusted to a position approximately 445 nm east-northeast of Chuuk. Slow strengthening was forecast, and JTWC upgraded TD-28W to a 35-kt tropical storm at 16/0600 UTC. JMA followed suit six hours later, naming the system Nock-ten. The newly-christened Nock-ten intensified at a rate of 5 kts per warning until it was on the verge of becoming a typhoon at 17/1200 UTC. Late on the 17th, the storm turned more southwestward, its forward speed once again slowing to around 4 kts. The system was promoted to a 65-kt typhoon at 18/0000 UTC. A sluggish southwesterly heading was still evident, but this progressively veered towards the west as the day wore on.

The 18th was the day of the most significant intensification that Nock-ten underwent in its entire lifetime. The MSW rose to 85 kts at 18/1200 UTC, but there was to be no further strengthening until 19/0000 UTC. At this time, the cloud-filled, ragged eye associated with Typhoon Nock-ten was located 300 nm southeast of Guam. It was still tracking in a westerly direction at a faster pace, but once again the storm stuttered. However, Nock-ten soon accelerated again and curved onto a west-northwest to northwest track in response to a change in the position of the steering ridge caused by a trough crossing Japan, plus the remnants of Typhoon Tokage. Typhoon Nock-ten returned to the slow strengthening habits of its earlier days with an increase of only 5 kts during the 19th and 20th. The MSW held at 95 kts through the 20th as the storm wobbled on its west-northwest to northwest path, passing 160 nm south of Guam at 20/0000 UTC.

Typhoon Nock-ten remained stuck at 95 kts through the 21st, apart from a slight dip in intensity to 90 kts at 1200 UTC on 21 October. The storm recovered this small deficit and re-strengthened back to 95 kts six hours later. The system finally intensified into a 100-kt typhoon at 22/0600 UTC as it headed northwestward approximately 780 nm to the southeast of Okinawa, Japan. Nock-ten then turned west-northwestward late on the 22nd and continued this track through the next day, reaching a peak intensity of 110 kts at 23/0000 UTC. This was maintained for twelve hours, the MSW falling slightly to 105 kts at 23/1200 UTC. At this time, Nock-ten was tracking 480 nm south of Okinawa.

Remaining a 105-kt tempest for the next day or so, Nock-ten began to tire at 24/1800 UTC when the tropical cyclone's continued northwestward heading brought the eye within sight of Taiwan, centred about 160 nm to the south-southeast of Taipei. Changing onto a northerly track, Typhoon Nock-ten made its closest approach to Taipei between 25/0000 UTC and 25/0600 UTC as its MSW fell below 100 kts. At 0600 UTC Nock-ten's centre lay just off the northeastern tip of Taiwan. The storm began to significantly weaken as it pulled away from Taiwan and by 25/1200 UTC the intensity had dropped to 65 kts, the track recurving onto a north- northeasterly heading. JTWC downgraded Nock-ten to a tropical storm at 25/1800 UTC and issued their final warning six hours later, locating the centre 150 nm northwest of Okinawa. Nock-ten's forward speed towards the east-northeast had accelerated to around 26 kts at this time. JMA released their last bulletin at 26/0600 UTC and followed the extra- tropical LOW and its associated gales into the North Pacific.

At its maximum intensity, Typhoon Nock-ten's wind field was representative of a small to average-sized system. Typhoon-force winds extended 20 nm in all directions while gales reached out as far as 100 nm in all but the southeast quadrant where they lay up to 110 nm from the centre.

JMA estimated a peak intensity of 85 kts (10-min avg) and a minimum CP of 945 mb. The maximum intensity estimated by PAGASA during the time that Typhoon Nock-ten was within their area of responsibility was 80 kts. (The system was christened Tonyo by that agency.) Both HKO and CWB estimated their highest MSW at 85 kts while NMCC assessed Nock-ten as a 90-kt typhoon.

Damages and Casualties

Typhoon Nock-ten lashed northern Taiwan with powerful winds and driving rain, disrupting international flights and closing financial markets, schools and government offices. Three fatalities occurred as a result of flash flooding.

Huang Chunliang Report

Following are the reports compiled and sent by Huang Chunliang of Fuzhou City, Fujian Province, China. A special thanks to Chunliang for compiling and sending the information. (To convert wind velocity in metres/second (m/s) to knots, divide m/s by 0.51444, or for an approximation, simply double the m/s value.)

(a) Report from China

{Part I}. Landfall

According to the CWB warnings, Moderate Typhoon 0424 (Nock-ten) 
made landfall in northeastern Taiwan between Tou Cheng and 
Santiaochiao around 25/0230 UTC with a MSW of 40 m/s and a CP 
of 950 hPa.  The typhoon then entered the water north of Taiwan 
from between Tanshui and Fukueichiao around 25/0515 UTC before 
recurving and accelerating to the northeast.

{Part II}. Meteorological Obs from Taiwan

1. Daily Rainfall [23/16-24/16Z] (only Top 5 listed)

Ranking     Station ID              City/County         Rainfall (mm)
01          CWB 21C09               Taoyuan County      186.0
02          CWB C1U50               Ilan County         176.0
03          CWB C1A66               Taipei County       139.5
04          CWB C1A64               Taipei County       124.0
05          WMO 46691 (An Bu)       Taipei City         123.5

2. Daily Rainfall [24/16-25/16Z] (only Top 5 listed)

Ranking     Station ID              City/County         Rainfall (mm)
01          WMO 46691 (An Bu)       Taipei City         322.0
02          CWB C0A88               Taipei County       312.5
03          WMO 46693 (Chu-tzu-hu)  Taipei County       280.5
04          CWB 01A21               Taipei County       280.0
05          CWB 01A42               Taipei City         266.0

3. Peak Sustained Winds & Gusts

Only those stations that reported peak gusts greater than typhoon
force are given:
                                     Peak SW           Peak Gust
Station                           (mps/dir/Date)    (mps/dir/Date)
Lanyu (WMO46762/59567, Alt 325m)  36.2/ 30/24th     54.4/ 60/24th
An Bu (WMO46691, Alt 1450m)       ----/---/----     34.9/ 10/25th
Taipei (WMO46692/58968, Alt 9m)   13.8/ 40/25th     32.8/120/25th
Keelung (WMO46694, Alt 3m)        23.8/ 60/25th     47.3/ 50/25th
Ilan (WMO46708, Alt 7m)           25.4/360/25th     44.8/ 20/25th
Suao (WMO46706, Alt 3m)           29.7/270/25th     55.1/ 90/25th

Note: Dates given in the above table are local dates.

{Part III}. Meteorological Obs from Zhejiang

Significant gust obs included: Dachen Dao--29.9 m/s and
Shengsi--27.6 m/s.

(b) Report from Japan

1. Yonagunijima, Okinawa (WMO47912, 24.47 N 123.01 E, Alt 30m)

Peak sustained wind:  27.7 m/s [25/0000Z]
          Peak gust:  43.5 m/s [25/0032Z]
torm total rainfall:  97.5 mm  [23/1600-25/0900Z]

2. Iriomotejima, Okinawa (WMO47917, 24.39 N 123.75 E, Alt 9m)

Storm total rainfall: 111.0 mm  [23/1600-25/0400Z]
Peak hourly rainfall:  75.0 mm  [25/0108-25/0208Z]

3. Tanegashima, Kagoshima (WMO47837, 30.73 N 131.00 E, Alt 17m)

24-hr rainfall: 133.5 mm  [26/0000-27/0000Z]

(Report written by Kevin Boyle with significant contributions by Huang Chunliang)

Source: Gary Padgett's Monthly Tropical Cyclone Summary - October 2004

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