Category Archives: Tropical Cyclones

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

USA Hurricanes 29 August to 3 September 2016

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HurricaneMadelline

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HurricaneLesterCat3

HurricaeLesterCat4

MadellineWorldview

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Hermine

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During the past 7 days, no less than 3 hurricanes have impacted areas within the United States or waters under the jurisdiction of the United States.

There were two significant storms that threatened Hawaii and at one stage, both systems approached the Hawaii Islands only to veer north and south to avoid a direct impact across the islands.

Another hurricane made landfall across the Florida panhandle becoming the first hurricane to make landfall in 11 years since Hurricane Wilma. That was a short lived storm and it only reached Category 1 on the Saffir Simpson Scale. Its greatest impact was heavy rain and flooding that it brought.

The names storms were:-

Hurricane Madelline

On August 29, a very small hurricane had reached Category 4 on the Saffir Simpson Scale as it approached the largest of the Hawaiian Islands. The storm then veered more west south west but lost its intensity just to the south of the big island. As such, the big island was spared a direct hit although the rain bands did impact the island.

Hurricane Lester

Following on the trail of Hurricane Madelline, another small but powerful storm also reached Category 4 on the Saffir Simpson Scale. The named storm Lester also approached the Hawaii Islands but veered more north west. The storm is expected to pass just to the north of the islands. The storm is now weakening as it makes its closest approach to the islands.

Sea surface temperatures around Hawaii are between 27C and 28C, just enough to sustain such storms but it is rare to have two named storms at the same time threatening the islands.

Hurricane Hermine

This is the storm that is providing media attention across the United States as this is the first storm to cross the Florida coastline in 11 years. The storm formed just off the coast of Florida so its lifespan was short. There was not enough time for the storm to develop further due to its location so close to the coastline.

The storm barely reached Category 1 on the Saffir Simpson Scale sustaining winds at peak intensity 68 knots (Approximately 125 km/h). The biggest impact was the rain it produced. The storm has caused flooding in affected areas.

As shown on the National Weather Service Rainfall map of south east United States, up to 6 to 8 inches (150 to 200 mm) of rain has fallen in areas across south west Florida. While there are small pockets where 8 to 10 inches (200 to 250 mm) fell, the storm mostly produced rainfall of between 75 mm and 150 mm. The storm is now tracking north east through the Carolinas as a much weakened system.

CREDITS

1 - CIMSS For forecast plots (Various).
2 - NASA “Worldview” with overlays of Hurricanes Madelline and Lester acquired 30/8/2016.
3 - National Weather Service (Rainfall data for Florida) acquired 2/9/2016.

Hurricane Gaston forms outside the tropics 27 August 2016

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GASTON

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SatelliteGaston

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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HurricaneBlas6J

CloseupHurricaneBlas

HurricaneBlas1

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.

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