Category Archives: Tropical Cyclones

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

Hurricane Gaston forms outside the tropics 27 August 2016

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There have been a number of hurricanes this season within the Atlantic Ocean but as usual, they have mainly affected oceanic regions within the tropics or regions adjacent to the tropics. So far this season and notwithstanding recent flooding events across Louisiana and southern United States, the United States has not been affected by such storms to any degree.

A tropical storm at latitude 30 degrees north and longitude 54.6 degrees east within the mid Atlantic Ocean has transitioned into a small hurricane. This is unusual as the development has taken place well north of the Tropic of Cancer. What makes this storm even more unusual is its suggested forecast model for the next two days. The CIMSS forecast model suggests that the storm will remain at hurricane strength even at latitude 35 degrees north.

The storm is expected to reach peak intensity within 2 days with forecast winds to reach 90 knots at the centre (Approximately 167 km/h) as a Category two system on the Saffir Simpson Scale. The storm is well supported by sea surface temperatures of 29C to 30c even this far north. Given the right environment, the storm is capable of being sustained. Waters of 28C are reaching as far north as 37 degrees north of the equator within the region.

This is only a small hurricane but there is clear convection occurring at or near to the core although an eye cannot be seen. The storm is expected to track north west then be steered more to the north east as a weakening hurricane as it approaches 37 degrees north.

The satellite photo of the storm from NASA Worldview shows the storm clearly with convection visible. The storm is expected to remain over open ocean during its life span as a hurricane and thus not affect a population centre.

CREDITS

CIMSS Forecast model of the storm acquired 27/8/2016.
NASA Worldview of the storm with overlays acquired 27/8/2016.

Hurricane Blas Eastern Pacific Ocean July 5 to 9 2016

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While Typhoon Nepartak was gathering strength across the north western Pacific Ocean, another storm across the tropical eastern Pacific Ocean reached Category 4 on the Saffir Simpson Scale. The storm was named Hurricane Blas.

The storm is now going into decay.

Hurricane Blas developed over open ocean well to the west of Central America then travelled north west and is now in decay as it is encountering colder waters. The storm has not been documented in the media to any significant degree because it has not made landfall and unlikely to do.

At its peak strength, the storm sustained winds of 127 knots (Approximately 235 km/h) with peak gusts to 130 knots (Approximately 240 km/h) making it formidable in strength. On July 8, the storm is encountering oceans with a maximum temperature below 25 degrees at latitude 18.8 degrees north and 130.7 degrees east. The storm is unlikely to survive much longer given its environment.

Images of the storm at peak strength are attached which shows a classic galaxy like system and a well developed eye.

Another storm following in its wake is struggling to form but it has been named Tropical Storm Celia. The storm is taking time to form and should it transition to a hurricane then according to models, it is likely to be relatively weak and not exceeding Category 2 on the Saffir Simpson Scale. This is partly due to oceanic waters within the region being only 25 to 28C. The storm is unlikely to make landfall at the present stage.

Credits

1 - CIMSS Images of Hurricane Blas and forecast plot acquired 6 July 2016.

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.

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