Hurricane Alley is getting active!

Satellite image (courtesy of NOAA) on 31 July 2012 showing two large cells of disturbed weather in the North Atlantic tropics

One third of the 2012 Atlantic Hurricane season is done and the record shows only four named storms in what has been somewhat of a strange season, so far. There have been three tropical storms and a hurricane. Two of the tropical storms, ALBERTO and BERYL were generated respectively on 20 May and 26 May, before the ‘official’ start of the Atlantic hurricane season on 1 June, 2012. The last time we had two ‘pre-season’ storms was in 1908 when a hurricane activated on 6 March followed by another hurricane on 24 May, so this is a rare occurrence indeed. Then there was Hurricane CHRIS, and extra-tropical cyclone that originated at LAT 39N LON 58W, over the open waters of the Atlantic, an area not really known as a source of cylogenesis. The last activity so far this season was tropical storm DEBBY in the Gulf of Mexico, which generated on 24 June at LAT 26N LON 87W. This was followed by what has been a rather quiet month of July.

GOES satellite image of 31 July 2012 showing water vapor in the atmosphere over a portion of the Atlantic basin where a tropical wave with a center of low pressure is riding along Hurricane alley toward the Lesser Antilles, while another area of disturbed weather is affecting Hispaniola, Puerto Rico and the Virgin Islands
Color-enhanced infrared satellite image (NOAA) on 31 July 2012 showing a portion of Hurricane Alley, the Eastern Atlantic, and the western range of the Tropical-wave Assembly Line over Equatorial Africa

As the season has progressed we have kept an eye on several atmospheric and oceanic features representing potential contributors to cyclogenesis in the Atlantic basin, which include Hurricane Alley, the Tropical-wave Assembly Line over Equatorial Africa, the Belt of Tropical Activity and Sea-surface Temperature over the tropical North Atlantic ocean. While these features have been mainly quiet during the first two months of this 2012 Atlantic hurricane season,there have been recent signs of activity, which may signal the inception of new and more active phase in the 2012 season.

Over the past couple of weeks there has been increased generation of storms cells and larger tropical waves over Equatorial Africa coupled with a gradual shift of such activity toward the north. Both of theses conditions are much closer to the norm of what we expect to see over that region at this time of the year, than what we have seen over the past two months. What this means is that the Tropical-wave Assembly Line over Equatorial Africa  appears to be reaching a phase where we could expect to see a more continuous generation of larger and regularly spaced tropical waves marching westward toward the warm waters of the Eastern Atlantic near the Cape Verde Islands.

Because the Tropical-wave Assembly Line feeds into the Eastern Atlantic Ocean and the 5,000 kilometer-long ocean corridor extending from the western coast of Africa to the Lesser Antilles and the Caribbean, which we designate as Hurricane Alley, we could expect that increased storm activity in the Tropical-wave Assembly Line to reflect in increased tropical-wave traffic along Hurricane Alley. In turn these conditions also increase the probability of tropical cyclone generation, what we know as cyclogenesis, to also increase. This is exactly what we are starting to see happening along Hurricane Alley.

On 30 July a large tropical wave emerged over the Eastern Atlantic to the south of the Cape Verde Islands and continued moving westward along Hurricane Alley, where surface water temperatures are close to 30 Celsius. As of today 31 July 2012 this specific tropical wave is generating plenty of disorganized storm activity and showers associated with an area of low pressure as it continues to move westward at around 20 kph. This system is moving into an atmospheric environment of low wind-shear from its current location some 3,000 kilometers east of the Lesser Antilles well into the Central Caribbean. Despite the presence of areas of somewhat dryer air ahead, the combination of low pressure, rain cells and thunderstorms, high sea surface temperatures and low wind shear along most of its path, create conditions that may favor tropical cyclone development over the next 48 – 72 hours.Based on these evolving tropical conditions in Hurricane Alley, all interest in the Caribbean and Mexico, and USA states in the Gulf of Mexico and Atlantic states will be well advised to pay attention to the progress of this tropical wave closely over the next couple of days.

In monitoring how this tropical wave evolves over the next few days, it is also important to consider how other atmospheric features in or near the larger basin may affect it. By way of example, there is another large area of disturbed weather extending from the northern Windward  Islands and the Virgin Islands to Puerto Rico and Hispaniola, which may affect conditions ahead in the path of the particular tropical wave, especially over the central Caribbean sub-basin. There is also a area of strong rain and thunderstorms over the coastal Gulf states of Louisiana, Mississippi, and Alabama, moving toward the Gulf of Mexico and Florida, which may alter atmospheric conditions ahead of the system.

In a few days we will know if the potential interaction of various atmospheric features, and their eventual coincidence or lack thereof, will contribute or not to cyclogenesis around the tropical wave we are watching . In the meantime, relative to these happenings, it is important to keep in mind how many factors that may promote or adversely affect tropical cyclone generation must come together ‘correctly’ for a tropical cyclone to activate. In this regard a level of uncertainty remains relative to how global climate change may be affecting the whole process of cyclogenesis in the Atlantic and worldwide.

Satellite image (NOAA) of 31 July 2012 showing the Northwestern Pacific Ocean where category 1 Typhoon SAOLA is approaching the eastern coast of TAWAN and the Philippines, while Tropical Storm MANREY is near the southeastern coast of Japan, and a large area op disturbed weather extends for 5,000 kilometers toward the central Pacific

Elsewhere in the world, the ‘hot spot’ of cyclonic activity in the northwestern Pacific Ocean, continues to exhibit a high potential for cyclogenesis with two named-storms, Typhoon SAOLA active near the eastern coast of Taiwan, and Tropical Storm MANREY close to the southeastern coast of Japan. This is in addition to a rather large and elongated area of disturbed/stormy weather extending for more than 5,000 kilometers over the open waters of the western Pacific Ocean west of the Philippines, which overlaps with the Belt of Tropical Activity that now extends some 24,000 kilometers, more than half around the world, from the western coast of Africa to the Philippines.

Satellite view (NASA) of the full disc of Earth on 31 July showing the Pacific basin and the Belt of tropical Activity extending along the northern tropical region
Satellite image (NASA) of 31 July showing the full disk of Earth and the Atlantic Basin with the Belt of Tropical Activity extending across the northern tropics

While watching Nature at work in the tropical regions of Earth, and considering what the remainder of 2012 has in store for us by way of tropical cyclone activity, let us keep in mind that we live in vulnerable communities and that it takes, but just one impact by a tropical cyclone, regardless of intensity to see plenty of damage and human suffering, not to mention the high risk to human life and the environment. In consequence, we must pay attention, remain prepared, and engage in the practice of mitigation on a continuous basis!

On 1 August 2012: We have tropical depression #5 of the Atlantic Hurricane season!

Although during the night from 31 July to 1 August the tropical wave riding ‘Hurricane Alley’ became somewhat disorganized to the point that it looked rather ragged this morning, it encountered a favorable atmospheric environment with low wind shear, rather warm sea surface temperatures, and plenty of moisture and storm cells later on during the day, which induced strengthening and much better organization around the area of low pressure.

As of 1700 this 1 August the system has been classified as a Tropical Depression, the fifth of the 2012 Atlantic Hurricane season, while it is some 1,300 kilometers east of the Windward Islands moving generally to the WNW at 26 kph.  Maximum sustained surface winds range around 55 kph, with higher gusts. Based on current characteristics and continued favorable conditions along its immediate path ahead, it appears this tropical depression may reach Tropical Storm strength in the next 12 to 24 hours by the time it would be directly impacting the Lesser Antilles.

Below is a five-day forecast track for this tropical depression #5 published by NOAA’s National Hurricane Center at 1700 this Wednesday 1 August 2012. According to the NHC’s discussion the forecast models are in discrepancy as to what may happen after two days in the forecast period, with some models favoring further strengthening and others more of the same or even some weakening as the system would move into the central Caribbean. As it is known, the uncertainty in the forecast increases with time, consequently we will just have to continue monitoring this one closely while the models resolve their differences as they acquire additional data from the various observation platforms.

Five-day forecast track for tropical depression #5 of the 2012 Atlantic Hurricane season published by the National Hurricane Center on 1 August 2012 at 1700

From the five-day forecast above we can see the cyclone is expected to become a hurricane toward the end of the forecast period as it approaches the vicinity of Jamaica. While there is quite a bit of uncertainty regarding how this system would have evolved five days hence, it is important that all interests in the Caribbean, including Central America, Belize, Quintana Roo in Mexico, and Cuba pay close attention to how this system evolves as it progresses through the Caribbean. Interest in Florida and around the Gulf of Mexico also need to monitor this storm and be ready to activate emergency plans as needed.

Along these lines it is also important to note that two additional tropical waves have emerged from Equatorial Africa over the warm waters of the Eastern Atlantic and are now following the same path traveled by what is now Tropical depression #5. So there is plenty more seeds for potential tropical cyclone development as we approach the 20th anniversary of Hurricane Andrew, which devastated a good portion of Southeast Florida before also hitting Louisiana in August of 1992.

One thought on “Hurricane Alley is getting active!”

  1. As of 2000 EDT NOAA’s NHC gave the tropical wave mentioned in this post a 50% probability of developing into a tropical cyclone within the next 48 hours. The system has become much better organized with rain shower and thunderstorm activity getting more intense around the center of low pressure within the system. The forward speed of the system has also increased to around 30 kph, as it continues its westward progress toward the Windward Islands and the Caribbean, into an oceanic-atmospheric environment that is generally favorable for further development. As the title of the post says..”Hurricane Alley is getting active!”