Tag Archives: Tropical-wave Assembli line

2012 Atlantic Hurricane Season: 40% done!

On this Tuesday 14 August 2012 we are approaching the 20th anniversary of Hurricane Andrew, which devastated Homestead, Florida City and part of Miami the 24th of August 1992 to then continue across the state and the Gulf of Mexico to make a second landfall in Louisiana. Perhaps more importantly, for the 2012 Atlantic hurricane season, we mark 75 days or 40% into the current season as we also approach a 45-day period that historically marks the time of the year when the majority of Atlantic hurricanes form. This means  that 40% of the season is done with, but we are about to enter the period of higher risk relative to potential hurricane impacts. The figure that follows [from NOAA – Historical Climatology Series 6-2: Tropical Cyclones of the North Atlantic Ocean, 1851-2006, Page 24, Figure 8] illustrates how the period from 20 August through 1 October marks the peak of the annual Atlantic hurricane season, based on 137 years of records.

As we approach these important Atlantic hurricane milestones, I thought it would be a good idea to put the 2012 Atlantic Hurricane season in context by taking a look at what is happening now in the worldwide tropics.

For starters the Atlantic basin appears to be rather quiet with no major tropical cyclone activity currently under way. There is a large region of disturbed weather off the eastern coast of Nicaragua and Honduras stemming from the remnants of Tropical Depression #7, which had largely dissipated after crossing from the Atlantic into the Caribbean over this past weekend. This storm is moving generally westward with very little chance of cyclonic development before it crosses overland in central America, where it is expected to generate heavy rains and blustery winds for the remainder of this week.

GOES satellite image [courtesy of NOAA] of 14 August 2012 showing a re-generated Tropical Depression #7 in the Caribbean approaching Central America and several other tropical waves and low-pressure cells around the larger Atlantic basin
Also in the Atlantic basin there is a region of disturbed weather associated with a cell of low pressure some 1,600 kilometers southeast of Bermuda, over the open waters of the Atlantic, moving toward the northwest with a low probability (30%) of tropical cyclone development as the system will move into an atmospheric environment of dryer air and wind shear, although other factors such as the system moving into a much warmer section of the ocean may contribute to an increase in the probability of cyclonic development over the next 48 hours. Beyond this, there are a couple of rather weak tropical waves in Hurricane Alley and other weak and disorganized tropical cells over Equatorial Africa, which currently do not show much in the way of potential for further development over the next couple of days.

Tropical Storm Hector’s track as of 14 August 2012 developed by the U.S. Navy Research Laboratory based on data from NOAA

Over in the northern east Pacific Tropical Storm HECTOR is some 600 kilometers off the Pacific coast of Mexico moving westward at 10 kph with maximum sustained winds of 75 kph and higher gusts. In the same region, to the southeast of T.S. Hector’s current location off the coasts of Central America there are several areas of disturbed weather generating rain and thunderstorms in a feature that has persisted in that region for a few months already in 2012, and for much of the seasons over the last 2 – 3 years.

Track for Tropical Storm KAI-TAI on 14 August 2012 developed by the U.S. Navy Research Laboratory based on data from NOAA

At the other extreme of the Pacific Ocean, over the northwestern Pacific, Tropical Storm KAI-TAI is moving generally northwestward between the Philippines and Taiwan toward landfall in China, following a course recently traveled by other tropical cyclones. To the west of the Philippines and extending for more than 5,000 kilometers into the central Pacific we continue to see a large an elongated mass of disturbed weather, which has been a persistent feature in that region over the past several weeks.

Satellite view of 14 August 2012 [courtesy of NOAA] showing the eastern north Atlantic and the western rage of Equatorial Africa where the ‘Tropical-wave Assembly Line’ now reaches to 20 degrees of latitude North

Rounding-up this overview of current tropical cyclone activity worldwide it is interesting to note that the Tropical-wave Assembly Line over Equatorial Africa has continued its northward drift, and it now reaches to the latitude of 20 degrees North. The Belt of Tropical Activity continues to extend from the Eastern Atlantic to the far western Pacific, while showing particular strength across much of the Pacific.

Full Earth disk satellite view [courtesy of NASA] of 14 August 2012 showing the ‘Belt of Tropical Activity’ extending across much of the Pacific Ocean as well as Tropical Storm HECTOR currently active near the coast of Mexico
Full Earth disk satellite image [courtesy of NASA] of 14 August 2012 showing the western hemisphere and the ‘Belt of Tropical Activity’ extending from the Eastern Atlantic well into the Pacific Ocean
 

A final piece of information to complete this overview relates to the status of sea surface temperatures over the northern Atlantic. From the satellite image and overlay of sea surface temperatures that follow, it is clear most of the northern Atlantic basin has warmed-up considerably over the past few weeks, especially in its eastern region where cooler waters had persisted until recently. This image also shows increasingly warmer waters along ‘Hurricane Alley’ and in the Gulf of Mexico, which provide one of the required components for cyclogenesis as we approach the historical peak of the annual Atlantic hurricane season.

Satellite image of 13 August 2012 [courtesy of NOAA] with an overlay of sea surface temperatures across the northern Atlantic basin showing waters at or above 30 Celsius along ‘Hurricane Alley’ and a good portion of the Gulf of Mexico
 This is what is currently happening in the worldwide tropics in terms of tropical cyclone activity. With almost 2/3 of the year 2012 already gone, it would appear we may be looking at a third consecutive ‘sub-par’ annual worldwide season in terms of tropical cyclone generation. As of 14 August there have been a total of 43 named tropical cyclones worldwide, which is far below the annual worldwide average over the past 50 years or so. We will have to wait and see what happens in what remains of 2012, not only in the Atlantic and the current ‘hot spots’ over the northwestern Pacific, but also in the Southern hemisphere as activity there should start to pick-up again toward the end of the year.

As we get ready to commemorate the 20th anniversary of Hurricane Andrew, and prepare for what the peak of the Atlantic hurricane season may bring in terms of tropical cyclone activity, let us not forget that it only takes one impact by a hurricane, of any category, to cause considerable damage to buildings and property, untold human suffering, and high risk to life. Consequently we must remain alert, always be prepared, and continue to practice hurricane mitigation in order to reduce the potential for damage from recurring hurricane impacts.