vertical shear

2014 Atlantic Hurricane Season Officially Over

The 2014 Atlantic basin hurricane season will officially end just before the stroke of midnight Sunday, November 30th.

This will be a record breaking season as it has been nine years since a major hurricane (category 3 or higher) made landfall along the U.S. coastlines. Hurricane Wilma in 2005 was the last one to do so. Not that anyone wants a major hurricane on their doorstep but it is very unusual to have a nine-year period without a major hurricane reaching the U.S. soil. This year, the Atlantic basin had eight named storms, six of them becoming hurricanes. Two became majors, Hurricane Edouard was a category 3 but far out in the Atlantic and Hurricane Gonzalo briefly became a category 4 but weakened to a category 2 as it clobbered Bermuda.

Hurricane Arthur was the only storm to make U.S. landfall as it hit North Carolina as a Category 2 storm and winds of 100 MPH. Hurricane Arthur was also the strongest U.S. landfall since Hurricane Ike hit Texas on 2008.

So what happened this season? Most tropical disturbances form as they come off the coast of Africa or in the Central Atlantic (also know as the MDR or Main Development Region). This year there were a few inhibiting factors such as dry air, strong vertical wind shear, and a lot of sinking air.

Dry air and SAL were some of the reasons development was very difficult during the beginning and middle of the season. The SAL or Saharan Air Layer inhibited development of tropical waves. The vertical wind shear causes winds blowing from opposite directions to possibly rip a storm apart or temporarily pause any further development. Sinking air or convergence will not allow thunderstorms to rise which is essential for tropical cyclone development.

In the latter portion of the season, there were a few storms that did develop, some due to the MJO. The MJO allowed upward motion allowing thunderstorms to develop.

Although early indicators did seem that a El Niño was forecast to develop but although temperatures in the Pacific were higher than the norm and the atmosphere did not follow along. The forecasted El Niño never did come to fruition and never was an inhibiting factor and had little impact in tropical cyclone development in the Atlantic.

In the Eastern Pacific (EPAC) and the Central Pacific was just the opposite and tropical cyclone activity was extremely busy. The Pacific had weak vertical shear, and unstable air, the Pacific was the busiest in several decades. The East & Central Pacific had 6 tropical storms and 16 hurricanes, nine of them majors. Mexico was hit several times, Hurricane Odile being the worst. Hurricane Odile made landfall near Cabo San Lucas with winds of 125 mph. Even Hawaii was threatened by 3 tropical cyclones, with Hurricane Ana just south of the Big Island. Hawaii was also hit by Hurricane Iselle, the first hurricane for Hawaii to have landfall since Hurricane Iniki in 1992.

Not to be outdone, the Western Pacific also is having a very busy season. In fact Tropical Depression Twenty Two-W is forecast to be a Typhoon and possibly may hit the Philippines (again). As of this date, the Western Pacific has had 21 named storms, 10 Typhoons, seven of them Super Typhoons (unofficially). The strongest was Super Typhoon Vongfong with maximum sustained winds of 130 MPH. Note: Once Vongfong had moved into the are of the Philippines, PAGASA (Philippine Atmospheric, Geophysical and Astronomical Services Administration) Vongfong was now under the authority of the Phillipines and renamed Ompong.


Hurricane Earl, TS Fiona, and now TD Nine

Since this is the peak of the Hurricane season the tropics are hot and the trains of storm keep coming off the coast of Africa.
Hurricane Earl is now down to a Category 3 storm and the east coast from NC to Nova Scotia may get some effects from Earl. Earl is over very warm waters and also has a very good Cirrus outflow in a directions with the exception of the south, but Earl is now experiencing some SW vertical shear of 15-20 knots. There is also some mid to upper level dry air which is wrapping around portions of the storm. This should continue for 36 to 48 hours, but after that Earl will be over some cooler SST’s and this should begin to drop the intensity levels. The forecast is for Earl to be extratropical within 96 hours.

Tropical Fiona has become better organized today. Fiona looks much better with the exception of mid level dry air in the northern quadrant. The forecast for Fiona also better than yesterday which has Fiona dissipating in 48 hours. Most of the latest guidance now believe that Fiona will be a hurricane short term – possibly as soon a late tomorrow even though Fiona is going though some moderate shear. Soon after, there will strong northeasterly shear, mostly due to strong upper level winds associated from Earl. The pattern in a few days has Fiona rapidly weakening.


The tropical wave that came off Africa yesterday and was designated as Invest 98L this morning has now been classified as Tropical Depression Nine. A deep-layered subtropical ridge will keep TD Nine on W track for the next few days. By days 2-3, the ridge will weaken slightly and this will slow down the storm and also let the storm track WNW. Later, by days 4-5 the ridge is expected to strengthen again., and the storm is forecast to accelerate some. The intensity is problematic as although TD Nine will be over very warm SST’s, TD Nine will be experiencing Moderate to Strong vertical shear along with a large SAL to the North and west which should inhibit some of the convection.
Models are having a very hard time trying to get a grasp on the storm so there will be some bias and error – wait a day or two to see what happens at that time.


Impressive wave

A new very impressive wave is just coming off western Africa coast and another is following it. Will it have a chance to develop it to something tropical?

At the moment I do not see the MJO (Madden Julian Oscillation) as a factor. During the summer the MJO has a modulating effect on hurricane activity in the Indian Ocean, the western and eastern Pacific and Atlantic basin.
The MJO is characterized by an eastward progression of large regions of both enhanced and suppressed tropical rainfall.

The SAL (Saharan Air Layer) maybe a factor. The SAL at times can be a very intense, dry and dusty layer of the atmosphere. This can suppress any tropical cyclone development. The image from CIMSS shows a major layer of dust in the Eastern Atlantic.

Vertical Shear is in the 15-20 knot range but is is decreasing as the wave moves westward.

The SST’s (Sea Surface Temperature) in the area are above average (anomaly) and are 28°-29° Celsius or (82° – 84° Fahrenheit). Tropical Cyclones tend to need a minimum of 26° Celsius and above for anything to develop.

It is still to early to what will transpire with this wave but this is the time of year when storms will soon be developing in the Eastern Atlantic rather than the Caribbean or Gulf of Mexico. My own feeling is that won’t develop and can be counted out for at least the next couple days or will dissipate entirely.