Category Archives: Tropical Cyclones

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

Tropical Cyclone Amos – A threat to Western Samoa April 22 to April 25 2016

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A new storm is gathering strength just to the west north west of the small South Pacific Islands of Western Samoa. This storm has been named “Amos”.

Considering its location and forecast track, it appears that this storm could threaten or significantly impact the islands in coming days. If the forecast models are correct and the storm maintains its forecast track then the western and southern side of Western Samoa could be impacted significantly by the storm. This would include towns such as Samataitai, Taga on Savai and Falelatai on Upolu.

On the island of Savai, Mt Mauga Silisili at 1,858 metres in elevation would serve to enhance rainfall while providing for rain shadows in other areas depending on the location of the storm.

The capital of Apia is located to the northern side of Upolu Island and may be spared the worst of any such storm due to a small mountain barrier lying to the south of the city.

The storm has just completed its transition to a Category 1 tropical cyclone on the Saffir Simpson Scale west north west of Western Samoa. The forecast model from CIMSS is suggesting peak strength being a Category 3 storm at the point where the storm makes its closest approach to Western Samoa.

A tropical cyclone must sustain winds of 65 knots (120 km/h) to be classed a category 1 storm. Forecast winds at the core may reach 105 knots or 194 km/h (Category 3) at the closest point the storm makes to both islands making it a dangerous storm and a storm that deserves attention.

Strong convection is occurring as the storm develops further. The environment is favourable and its position over seas of 30C to 31C in temperatures makes the location highly favourable to sustain such a storm. Its location so close to Western Samoa makes it a potentially dangerous storm for the islands.

Following its passage across the Western Samoa region, this storm is expected to track south east taking it over cold oceans where it will decay.

Note:- Due to the current location of the tropical cyclone, a direct satellite image of the storm is not available as it appears the location of the storm at 12.4 degrees south and 182.6 degrees east does not lie within the direct viewing range of NASA's TERRA or AQUA satellite networks.


1 - CIMSS (Forecast plot) for Tropical Cyclone Amos dated 22/4/2016.
2 - CIRA (NOAA) Satellites and information - Image acquired 22/4/2016.

Tropical Cyclone Fantala reaches Category 5 – April 18 2016

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Tropical Cyclone Fantala has become the most powerful storm this season across the southern Indian Ocean (South of the equator). This storm is now a serious threat to the northern coast of Madagascar with the southern outermost bands of rain and storms passing over the northern coast of the country.

The worst of the storm is out to sea and forecast models suggest the storm to stall then head back south east. This storm has already defied earlier models as it has:-

1 - Reached category 5 on the Saffir Simpson Scale.
2 - Has tracked much closer to Madagascar then initially expected.

As shown on the graph from CIMSS, there is evidence that the storm is sustaining winds of 150 knots at the core (Approximately 278 km/h) and it is possible that wind gusts are reaching as high as 175 knots or 180 knots (Approximately 324 to 333 km/h). This makes it a formidable storm and any landfall on Madagascar or populated nearby islands at this strength would be disastrous.

It appears that the storm is at peak strength and should commence a slow weakening but it will remain a significant threat to the northern and north eastern coasts of Madagascar for a few days.

The NASA satellite photo of the storm taken 17/4/2016 from MODIS Terra shows a thick circular cloud mass, deep convection and a well defined eye at the centre. The CIMSS infra red image equally shows an intense storm barely off the coast of Madagascar and direct north of Antsiranana.

An image of the storm from CIRA (Enhanced Infrared MODIS /AVH RR) clearly suggests a powerful and formidable storm (Date 18/4/2016).

It will be interesting to see what occurs given its proximity to landmasses and population centres over coming days.


1 - CIMSS (Forecast plot of the storm dated 18/4/2016).
2 - NASA (Worldview image) 17/4/2016.
3 - CIRA / NASA (MODIS) AVH RR 18/4/2016.

Powerful Tropical Cyclone Fantala April 16 2016

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Tropical Cyclone Fantala has morphed into a powerful Category 4 on the Saffir Simpson Scale storm east of Madagascar. On Friday 15 April, the storm was approximately 700 km offshore from Madagascar and during Saturday, the storm was moving west at 7 knots or approximately 13 km/h.

It is currently sustaining winds of 130 knots (Approximately 241 km/h) with stronger gusts of 160 knots (Approximately 296 km/h) near the core.

Within twelve hours, the storm could reach peak strength with winds of 135 knots (Approximately 250 km/h) with peak wind gusts of 165 knots (Approximately 305 km/h) at the core.

Given its location, forecasters would be watching this storm with great interest and any landfall onto Madagascar would be significant.

The CIMSS forecast model suggests uncertainty of its forecast track within the next two days and it is suggested that the storm will approach the north east coast of the country then cease its west / north west path. The model suggests the storm may track south east back out to sea and away from the country.

Certainly if this occurs, a weather related natural disaster would be averted. The next two to three days will be crucial to where the storm tracks.

The NASA Worldview image of the storm taken 15/4/2016 shows a powerful storm with a thick band of rain and storms surrounding a small but defined eye.

Certainly, this is the most powerful storm this season for the south Indian Ocean and it is one storm that deserves attention given its strength.


CIMSS (Infra red image and forecast track).
NASA Worldview (Image of Fantala) dated 15/4/2016.