Category Archives: Tropical Cyclones

A large circulation sproducing heavy rainfall, very strong winds and storm surges

Super Typhoon Nepartak makes landfall Taiwan 8/7/2016

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AN Oceanic BUOY located approximately 170 km south east of Taitung City (Taiwan) appears to have recorded data from Super Typhoon Nepartak as the eye passed over and survived its onslaught.

The BUOY Number NTU2 operated by the Taiwan University Institute of Oceanography Sea Automatic Weather Observation has survived sustained winds of at least 150 miles per hour and a possible gust of 153 miles per hour (Approximately 246 km/h). The problem of this data is that the readings are off the charts as shown so it is difficult to verify the true peak gusts.

Data from CIMSS suggest peak wind gusts of 152 knots (Approximately 282 km/h) at peak intensity.

The instrument that captured the winds is still recording after its direct encounter with the eye.

The same instrument recorded a central pressure of 897 HPA.

Super Typhoon Nepartak made landfall across southern Taiwan at around 6.30 am as a Category 4 storm. It weakened slightly just prior to landfall but still packing powerful winds. Rainfall across south east Taiwan has been heavy with one centre recording over 500 mm of rain between midnight and 7.10 pm.

The radar image shows a weaker storm (Now a Category 2 on the Saffir Simpson Scale) but with a large precipitation shield. The precipitation shield will traverse south east China where flooding is likely.

Heaviest rainfall from 12 midnight to 7.10 pm include:-

Liu Shi Dan Shan - 524 mm.
Shang Li - 476 mm.
Shao Jia - 436 mm.
Dian Guang - 433 mm.
Yuli - 430 mm.
Shoa Ka - 425 mm.

Many other weather stations recorded 200 to 400 mm partly due to the mountainous terrain of the country enhancing rainfall.

A major damage clean up will be required in the weeks and months following the storm.

Given the storms of 2015 and now this one, it shows that Taiwan is no stranger to powerful typhoons. The latest storm takes the tally to 3 such storms since 2015.

CREDITS

1 - Central Weather Bureau for radar image and rainfall data 8/7/16.
2 - CIMSS Wind data for Nepartak.
3 - Taiwan University Institute of Oceanography Sea Automatic Weather Observation.

Super Typhoon Nepartak July 5 to 8 Taiwan

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The drought of typhoons across the north west Pacific Ocean has finally been broken. The first significant storm of the 2016 season has developed south east of the Philippines and is travelling north west at a rapid pace. At the time of writing, the storm was located 645 nautical miles south east of Taiwan.

The storm has rapidly developed over oceanic waters of 31C or greater and is now known as “Super typhoon Nepartak”. It is travelling at 18 knots north west towards Taiwan and if it maintains its current track, it would strike the country's east coast late Thursday or early into Friday.

Super Typhoon Nepartak has a small eye and models show the storm sustaining winds near the core of 150 knots (approximately 278 km/h) with gusts to at least 170 knots (Approximately 315 km/h).

Within 24 hours, models suggest a storm with winds of 150 knots (Approximately 278 km/h) but with wind gusts approaching 180 knots (Approximately 330 km/h) close to the core.

This is a powerful storm but fortunately it is over open ocean. The CIMSS model suggests the storm sustaining Category 5 status right before it reaches the east coast of Taiwan. Fortunately much of the population of Taiwan live on the west coast with a mountain range offering some degree of buffer against the worst impacts of such a storm moving in from the Pacific Ocean.

The plots below show the storm in detail including a forecast model. Strong convection is occurring close to the core. This is one storm to be watched over coming days especially if it does strike the east coast of Taiwan. At this strength, there is potential for significant damage.

CREDITS

1 - CIMSS Forecast plot of Super Typhoon Nepartak acquired 6/7/2016.
2 - CIRA for satellite imagery acquired 6/7/2016.
3 - NASA (Worldview with overlays) acquired 6/7/2016.

Tropical Cyclone Amos hits Western Samoa April 23 2016

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Tropical Cyclone Amos has taken a slightly altered path when compared to the forecast model suggested by CIMSS dated 22/4/2016.

As a result, the core of the tropical cyclone is either likely to brush the north coast of the Western Samoa or pass right over one or both the islands.

The satellite photo from CIMSS shows the storm directly over Western Samoa as a category 2 storm on the Saffir Simpson Scale with winds reaching 90 knots (Approximately 167 km/h) with higher gusts to 110 knots (Approximately 204 km/h). Heavy rain is a feature and forecasters are predicting as much as 500 mm of rain over certain areas. Given the mountainous terrain of the islands, rainfall is likely to vary in places and rainfall may be enhanced on the windward side of the mountains while the leeward side has less rainfall.

Flooding, storm surge and some property damage is certain.

The storm as forecast appears to be reaching maximum strength at the point the storm makes its influence felt across the islands.

Using NASA's Worldview,Satellite image, the population centres of Western Samoa (Shown in red) have been overlaid across the image. Given that the storm appears likely to now pass / brush across the north coast, the capital Apia would be significantly impacted by the event.

Another island being American Samoa is also likely to be significantly affected by the storm.

The satellite image does not show a defined eye but strong convection showing storms is identified.

The image from NOAA (CIRA) shows the storm directly over Western Samoa suggesting either a direct hit or very close to one.

Once the storm moves away from the islands, it is expected to weaken as it tracks south east over colder waters.

CREDITS

1 - CIMSS (Images of AMOS) dated 23/4/2016.
2 - CIRA (NOAA) Image dated 23/4/2016.
3 - NASA (Worldview) Population overlays provided dated 23/4/2016.

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