Tag Archives: North America

Early 2013: Tropical Cyclone Activity in the Southern Hemisphere

Just a few days ago on 21 December 2012 the Earth’s axis reached its maximum tilt placing the ‘Tropic of Capricorn’ directly under the Sun, marking the onset of Winter in the Northern Hemisphere and Summer in the Southern Hemisphere.

With this event the oceans, which cover more than 80% of the Earth’s southern hemisphere, are receiving the maximum amount of Energy from the Sun continuing the warming trend started with the autumnal equinox in September of 2012. This natural annual cycle not only increases the sea surface temperatures, but it also increases the accumulated heat contents in the southern oceans and with it the potential for cyclogenesis in the ‘bottom’ half of our planet.

Today 2 January 2013 there are continuing signs that the southern tropics are indeed under the influence of factors that are usual contributors to cyclogenesis. Two tropical storms, tropical storm Freda in the South Pacific and tropical storm Dumile in the southern Indian Ocean, are currently active and threatening nearby islands. In addition there are two areas of low pressure and disturbed weather in the Indian Ocean and the South Pacific that are showing signs of strengthening and potential for cyclonic development, which warrant monitoring.

Color-enhanced infrared satellite image of the South Pacific on 2 January 2013 showing tropical storm FREDA over New Caledonia, and a cell of disturbed weather to its northeast, which may warrant further monitoring

Tropical storm Freda originated over the Coral Sea and earlier today was moving toward the southeast for possible landfall in New Caledonia with maximum sustained winds of 65 kph, gusting to 82-85 kph. While the storm is generating some heavy rains  around its center it appears to be weakening as it interacts with the island.

Color-enhanced infrared satellite image of the Indian Ocean on 2 January 2013 showing tropical storm DUMILE to the west of Madagascar, as it approaches the island of Reunion, and a separate cell of disturbed weather to its northeast that may develop further over the next day or so

Tropical storm Dumile was moving generally southward some 600 kilometers east of Madagascar on a course that threatens the island of Reunion in the southern Indian Ocean. The storm which is currently generating maximum sustained winds of 105 kph with gusts of up to 130 kph, appears to be strengthening and may reach hurricane strength within  the next 24-48 hours as it moves in a favorable environment.

Composite of satellite images creating a global mosaic over Australia, showing water moisture in the atmosphere to highlight the location of the tropical storms and cells of disturbed weather mentioned before

Elsewhere in the world conditions vary by region. Stormy conditions prevail over the northern latitudes across North America, Europe and Asia. A train of waves of disturbed weather continues to move eastward from the western Pacific region toward North America where their interaction with the jet streams has contributed to record snowfalls over vast portions of Canada and the United States.

Color-enhanced infrared satellite image showing the train of disturbed weather waves moving over the northern Pacific Ocean toward North America, where their interaction with jet streams has generated extreme stormy weather over large regions of Canada and the USA

In contrast with such prevailing conditions over the northern latitudes, most of the Atlantic Basin is under a regime of high pressure and dryer air with no storms present on this 2nd day of the new year.

Color-enhanced infrared satellite image showing the Atlantic basin north of the equator on 2 January 2013. Notice how clear and devoid of storms or disturbed weather cells the whole basis is on this day

While monitoring such current tropical activity pondering  what the rest of the year may bring in terms of tropical cyclone, it may be of interest to note that on a worldwide basis the year 2012 saw an increase in the total number of named storms after having shown a decline over the previous two years (2010 and 2011) to end just slightly below the average for the last fifty years or so. Based on this it could be said that we nearly had an average year in 2012 in terms of the total number of tropical cyclones on a worldwide basis.

Regarding the level of tropical cyclone activity in 2012 one significant change was a noticeable shift in the level of activity  toward the northern hemisphere. In 2012 we saw increases in the total number of named storms in the four basins for cyclogenesis in the northern hemisphere, from the total numbers generated in 2011. The eastern Pacific basin off the coast of Central America and Southern Mexico generated 17  tropical cyclones in 2012 versus only 11 in 2011, while the Northwestern Pacific basin saw a total of 25 tropical cyclones generated in 2012 versus 21 in 2011. The Atlantic basin increased from 18 named storms in 2011 to 19 in 2012, a slight increase  in total number of tropical cyclones, but perhaps the most noticeable change in this basin was the reduced level of intensity experienced as most of the cyclones generated did not reach hurricane strength, staying within tropical storm levels.

What do these numbers mean? What can we learn from the noticeable shift in tropical cyclone activity to the  northern hemisphere, where most of the world’s population lives?

One simple answer is that 79% of the total number of tropical cyclones generated worldwide in 2012 took place in the northern hemisphere, compared with an average of 69.3% in the past twelve years A(2001 through 2012) and only 62.2% in 2009, 66.7% in 2010 and 68.4% in 2011.  While these fluctuations may just be part of   the natural variability of cyclogenesis the reality is that the main drivers for this are not well understood.

Few or no conclusions can be drawn about the significance or this because of the extremely short time period being assessed, however  should this eventually develop into a trend toward more tropical cyclones in the northern hemisphere, even if most do not reach major hurricane intensity, residents in vulnerable communities in the USA and elsewhere would do well to start focusing much more intensely on preparedness and mitigation rather than on response. Relative to this it is critical for all to keep in mind that even a minor hurricane or a tropical storm are capable of inflicting considerable damage and human suffering, as it was so graphically demonstrated by the impact of Hurricane SANDY in 2012.

Be prepared! MITIGATE!

The cyclone that won’t go away!

Just about two weeks ago the tropical storm that became cyclone Giovanna generated over the central Indian Ocean near the equator. Since then this storm grew in size and strength reaching category 4 intensity one week ago before making landfall in Madagascar on 13 February, near the capital of Antananarivo. Weakened by its interaction with the topography of the island the cyclone still managed to traverse it to emerge over the Mozambique Channel the next day as a tropical depression.

Color-enhanced infrared satellite image showing two tropical cyclones active over the southern Indian Ocean on 20 February 2012

Once over the warm waters between the African continent and Madagascar the cyclone strengthened once again becoming a tropical storm and reaching category 1 strength on 19 February, which it maintained until earlier today 20 February 2012. The cyclone has been downgraded to tropical storm category and late in the day was moving generally south by southeast some 500 kilometers south of Reunion in the southern Indian Ocean. While it appears Giovanna will continue to weaken as it tracks over progressively colder waters, this storm has traveled close to 7,000 kilometers over the past 14 days.

Tropical storm Giovanna is being chased by a cyclone currently designated as Tropical Storm 13, which formed as a tropical depression over the south-central Indian Ocean some 4-5 days ago, and is near the island of Rodrigues in the Mauritius archipelago on 20 February 2012 moving in a generally southward track toward the course being followed by Giovanna.

Current cyclonic activity and the long lasting course of cyclone Giovanna are testimony of the coupled ocean-atmosphere condition that prevail over most of the Indian Ocean and the tropical South Pacific. Evidence of this cyclogenesis-favorable environment is apparent in the satellite image above, in the form of very cold cloud tops over a vast region of disturbed weather and rainfall reaching from the western Pacific across the Indian Ocean all the way to just off-shore eastern Africa.

Elsewhere in around the world the Caribbean and most of the tropical Atlantic basin north of the equator are calm and cool on20 February, but both the northeastern Pacific and Northern Atlantic are different stories. Over the Pacific it appears the Pineapple Express is quite active interacting with a polar jet stream near Alaska to create pulses of disturbed winter weather over large regions of North America reaching all the way into Texas and the southeastern USA. The satellite image below illustrates these conditions on 20 February 2012.

Satellite view for the aviation industry showing the calm, mostly col and dry Caribbean, Gulf and a good portion of the tropical Atlantic basin on 20 February 2012

Color enhanced infrared satellite image showing stormy conditions over portions of the northeastern Pacific Ocean and North America on 20 February 2012

These pulses of winter stormy weather are pushed beyond North America over the northern Atlantic and Europe beyond, where extreme weather events over the past few weeks have caused considerable damage and death in many areas. The satellite image below partially illustrates some of those prevailing conditions over Europe and beyond.

Color-enhanced infrared satellite image showing large regions of disturbed winter weather over the North Atlantic and Europe on 20 February 2012

The reality of this northern hemisphere winter in 2011/2012 is that it has been anything, but typical. Late in coming in some regions, extreme in others, warmer than usual, wetter than usual, rare etc. It is clear that patterns have been changing as the effects of global climate change are becoming more apparent.

What will the rest of 2012 brings us in terms of climatic conditions? What will happen by way of cyclogenesis around the various basins worldwide? Only time will tell, but if current and recent activities are any indication, it is certain to be interesting! Keep watching!