There are ‘signs’ stirring in ‘our’ northern tropics!

Today Thursday 19 April 2012 there are some atmospheric stirrings in the northern tropical Atlantic and over the northern tropical eastern Pacific oceans, which may lead one to ask if the hurricanes seasons of these two basins might be approaching their respective start blocks?

GOES satellite image of 19 April 2012 showing a the tropical north Atlantic and an area with potential for further development identified by the dotted yellow outline

Same satellite image of 19 April using a water vapor filter to detect moisture content in the atmosphere that also helps visualize the specific region of interest

One particular area of interest, shown on both of the GOES satellite images above, is located near LAT 30N LON 50W over the open waters of the central North Atlantic some 1,200 kilometers east by southeast of Bermuda; this appears to be an area of low pressure with large cells of disturbed weather, rain and thunderstorms on its periphery, which may warrant some attention by the folks at the National Hurricane Center [NHC], and by interests in the larger region such as the Bermudas, the Canary Islands and the Azores .

Color-enhanced satellite image showing a 4000 kilometer-long train or tropical waves ranging from the Atlantic to central Equatorial Africa on 19 April 2012

Of interest to Florida, Central America, Mexico’s Yucatan Peninsula, the Gulf of Mexico and island nations in the Caribbean, is the recent flare-up of tropical-wave production over Equatorial Africa and the southern limits of what is known as ‘Hurricane Alley’ in the tropical Atlantic north of the equator. Satellite imagery [see image above] shows a long train of stormy weather cells stretching more than 4,000 kilometers from the waters of the Atlantic to eastern Equatorial Africa. It would appear the ‘tropical-wave assembly line’ is starting to activate its production of tropical waves in a pattern that eventually makes its way toward the eastern Atlantic south of the Cape Verde islands, a known basin of cyclogenesis for tropical cyclones that usually aim for the Caribbean, the Gulf, Florida or the mid-Atlantic USA coastal regions.

Color-enhanced infrared satellite image of 19 April 2012 showing the Eastern Pacific where an elongated region of storm cells is present

Over on the other side, over the waters of the eastern Pacific [see image above]  off the coasts of Central America, which have been warming up quite rapidly over the past few weeks, there is another train of stormy weather cells reaching some 2,500 kilometers over the Pacific north of the Equator. One particular storm cell at the eastern end of the ‘train’ looks particularly menacing in terms of potential for generating extreme weather conditions.

Granted, all of my observations  above are solely based on a visual assessment of satellite imagery that document seasonal changes in atmospheric conditions and surface water temperatures over two basins that are known sources of cyclogenesis, but in my opinion it is clear some of the factors that contribute to cyclogenesis over the tropical North Atlantic and the northern Eastern Pacific have started to coalesce. It now remains to be seen, how other contributing factors fall into place or not, and how this may affect the start of the ‘official’ hurricane seasons in the eastern Pacific and in the Atlantic.

Satellite-based map of sea surface temperatures over the Atlantic and part of the eastern Pacific basins on 18 April 2012

Map based on satellite imagery of 18 April 2012 depicting sea surface temperatures over the Eastern Pacific

One such cyclogenesis-contributing factor is sea surface temperature, which becomes a positive influence once it reaches above 26 C. Recent sea-surface temperature maps based on satellite remote sensing show rapid sea surface warming taking place with the onset of spring in the northern hemisphere, particularly in the eastern Pacific. The waters of the Atlantic have warmed also, but a large region of cooler waters remains over the mid-northern Atlantic, which is expected to have somewhat of a dampening effect of tropical cyclone activity in the Atlantic in 2012.  Relative to the role of sea surface temperature (SST) as a contributor to cyclogenesis, research has shown that a much better indicator of ocean regions favoring cyclogenesis or the intensification of tropical cyclones is Sea Surface Height Anomaly (SSHA) because it also reflects the expansion of ocean waters under the effect of temperature, and consequently it is a much better indicator of the oceanic heat contents that can fuel a tropical cyclone.  For those interested in learning more about the use of SSHA as a predictor of tropical cyclone generation or intensification the following links will take you a very good source of specific knowledge in this field [EOS_FINALVol84Dec2003]

Satellite image of 19 April 2012 showing pulses of disturbed weather moving toward the central USA

While we initiate this hurricane season watch in the Atlantic and the Eastern Pacific on this 19 of April 2012, it is important to also watch the weather systems now moving over the continental USA. The GOES satellite image above shows a large mass of stormy weather moving toward the central USA toward a region that just a week ago was hit by devastating tornadoes and extreme weather. On the same image to the far left the next pulse of stormy weather is seeing just coming over the Pacific Northwest and Canada riding the jet stream toward the same region of the country mentioned before. So, it appears as if the atmosphere over the USA is staying in a pattern similar to what we had in 2011 around the same time, which may have the potential for generating extreme weather conditions over vast regions of the country.

The signals from Nature are clear: the potential for cyclogenesis continues to increase as we approach the end of the spring in 2012, while the potential for severe or extreme weather over vast regions of the continental USA has already been felt in several states and continues to be a threat.

In view of this situation it is important for residents of vulnerable communities everywhere in the USA to pay attention, to be prepared and to always practice MITIGATION!

REFERENCES:

GONI, G., [AOML, NOAA, Miami, FL], TRINANES, J. A., [CIMAS, UM, Miami, FL] Ocean Thermal Structure Monitoring Could Aid in the Intensity Forecast of Tropical Cyclones: EOS, Journal of the American Geophysical Union,  23 December 2003, Vo.l 84, Number 51, pp 573-520

National Remote Sensing Centre – Indian Space Research Organisation: March 2010 Proceedings of the Workshop on Utilisation of Satellite Derived Oceanic Heat Content for Cyclone Studies. Hyderabad, India.