SAL

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.

Share

Invest 93L & Large Tropical Wave

Invest 93L, the resilient tropical wave in the Caribbean, continue its westward motion it’s journey though the “Graveyard” where many storms either weaken or die. The trade winds in that area usually are much faster and especially weak storms are not able to develop roughly between 65°W to 75°W. Once again during the day today, 93L seemed to be developing somewhat albeit very slowly. From the CIMSS maps, there is an increase in the low level convergence (is where the flow over some area is moving inward toward that area) and there is also a marked increase of divergence (where the air at some particular level in the atmosphere over some area is moving outward or away from the area, on average). 93L also has a classic upper level anticyclonic high over it. During the latter portion of the day, 93L began to exhibit signs of cyclonic turning although very, very slowly – mostly in the mid to upper levels but there is no indication of low-level circulation.

Looking ahead, 93L will be dealing with dry air from the west. This will keep any development to a minimum for the next 24-36 hours or so. Shear in minimal so if 93L could get just get a low level circulation, conditions will be conducive for gradual development.

Tracking for 93L is pretty straight forward. Most models forecast that 93L will continue the westward motion toward Nicaragua/Honduras. If 93L were to develop into a very strong hurricane (which is not indicated), then a more poleward shift would result with a turn toward Belize. At this moment, model intensity keeps 93L below hurricane status or just minimal category one.


A large tropical wave southwest of the Cape Verde Islands is the next possible concern. Although it is surrounded by massive amounts of dust (SAL), as it gets closer to 55°W, two of the major models (GFS and ECMWF respectively) have it as a possible major hurricane north of the Leeward Islands with a very possible threat to Florida and also the Eastern seaboard. The ECMWF has been flipping during a few runs so we will have to see how things pan out in a few days. Just remember, these are LONG term models. It’s still way too early to panic but all those in affected areas should keep an eye on this system as it heads westward. If you have not begun to stock up of your hurricane supplies, now would be a great time to do so. The MJO for the next three weeks or so will be in a upward motion for the entire Atlantic basin. Upward motion has a tendency to allow for thunderstorm development. This is the time of year where development ramps up and the Atlantic basin is more active with tropical cyclones.

GFS RUNS

ECMWF RUNS

Share

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.

LATEST

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.

Share

Two New Tropical Waves

A very large tropical wave in the central Atlantic (located near 40°W) with some very good cyclonic turing is looking like something we need to keep an eye on eye. The wave has had problems with dry air lately. At the moment, the wave will continue to struggle but shortly thereafter, it will be in a better enviroment as upper level winds should relax and the wave will be more conducive for possible development.

Another wave which has just come off the coast of Africa is also another area that has to be watched. Some of the Global Forecasting models been to want to develop this wave. This wave also has some very good cyclonic turning. To the north and south of the wave there is some dry air but is minimal and the SAL is also at low levels. This has a chance to be the first CV (Cape Verde) system of the season. Given that most of the tropical waves previously had SAL or upper level winds that hampered any tropical devolpment, this wave should do much better.

Of the two waves, if one only had a chance to develop, the latter wave is the one I would have to choose.

Share

Tropics quiet

At least for now the tropics are somewhat quiet. There is a strong wave that is now moving into Central America. It won’t be able to develop while over land but once it emerges into the Pacific, the system may develop. There are a few models that are hinting that it will. Since most EPAC systems head west and don’t touch the US mainland, I mainly will be talking about the Atlantic basin.

A strong and organized wave has emerged off the coast of Africa. It is around 9 N latitude and that places well south of the SAL that has been in the Eastern Atlantic. The AEJ (African Easterly Jet) will help in building convection. There is a chance that it might develop and the GFS model thinks it just might do so.  For now I would give it a 30% chance. As it heads west – chances will probably drop unless it can maintain the convection.

Share

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.

Share