Greetings to everyone.
The 2014 Atlantic Hurricane Season is just around the corner, beginning June 1, and running through November 30.
I have been reviewing some various conditions, oscillations, and forecast parameters over the past few days, and will briefly explain a few conditions which have been occurring, and what some of the forecast trends currently look like, which reflect the storm totals in this seasonal forecast.
One of the main factors to start with, is the North Atlantic Oscillation (NAO). The following links explain the NAO: http://en.wikipedia.org/wiki/North_Atlantic_oscillation
Since the end of the 2013 Hurricane Season, the NAO has been mainly, on average, in the POSITIVE phase. What this means in a nutshell is, the Atlantic Subtropical ridge, or Azores high has caused stronger high pressure over the Atlantic Ocean / MDR. This has caused the MDR to remain cooler than average, and has allowed for drier air to continue over a good portion of the Atlantic, not unlike what we saw during 2013. The current forecast as of this morning, shows the NAO going NEGATIVE for a short time, then shifting back toward positive. SHOULD the NAO remain in a POSITIVE phase, vice NEUTRAL / NEGATIVE, this will again be a hindering factor in Atlantic activity.
You can see how the Equatorial Pacific is beginning to warm. You can also notice the wram anomalies strecthing from the U.S. west coast from CA. up to AK, indicating a WARM phase of the PDO (Pacific Decadal Oscillation) which I am sure will have an effect on global wind patterns.
Recent updates in the ENSO forecast indicate the climate models agree with the onset of an El Nino around JUL / AUG. El Nino explained: http://www.bom.gov.au/climate/glossary/elnino.shtml
During the onset of El Nino, warmer oceanic anomalies surface along the South American west coast, and extend west through the Equatorial Pacific Ocean So far, we have had 2 – 3 good westerly wind bursts from the downward motion phase of the MJO in the far western Pacific. This has allowed for “Kelvin” waves in the sub surface of the sea, to be forced toward South America. When this warmer water hits the coast (sub surface), the water erupts to the surface, and ricochets back toward the west, creating the familiar warm tongue we associate with El Nino. This can be gauged in part by the Southern Oscillation Index (SOI) diving negative. The SOI has recently recovered, however sustained westerly winds (NEGATIVE SOI) can create El Nino. This sends a tremendous amount of heat energy into the atmosphere near the South America. Convection builds, and the heat energy released from thunderstorms enhances and allows to persist, the subtropical jet, which is normally a winter time feature. The winds then, are stronger, and blow across the Atlantic Ocean, creating enhanced wind shear. This shear blows off the tops of the thunderstorms associated with any developing tropical systems in the Atlantic…the effect not only prevents organization, it spreads out the rising column of hot air over a greater area, not allowing it to concentrate directly over a disturbance.
The Indian Ocean Dipole last season was NEGATIVE to NEUTRAL. Albeit this condition does have a tendency to disrupt the West African Monsoon Circulation, it did not allow for heat to build up in the west Indian Ocean, which in turn, may account for the lack of Tropical Wave activity over the African Continent, due to the lack of tropical thunderstorms advecting toward the west from the Indian Ocean. A POSITIVE phase may in fact, aid in an increase of stronger tropical wave activity, but, has the tendency to disrupt the West African Monsoon Circulation. IOD explained: http://en.wikipedia.org/wiki/Indian_Ocean_Dipole
The SAL (Saharan Air Layer) [African Dust] had a hand in the reduction of hurricane activity last season. Through daily observations last year, the majority of the dust originated not so much in the western Sahel region, but somewhat farther north and east, as if a semi – permanent high was anchored in place, sweeping dust in a path as indicated:
It is however, unknown what SAL conditions may be encountered this season, albeit it is strongest in July…and for that reason, it is inconclusive at the moment of how the SAL or lack of may affect this season.
Upon performing careful analysis of the ONI (Oceanic Nino Index) values listed, based on both anomalies and / or similar trends as to the current El Nino forecast, the closest analog years that the upcoming season MAY resemble are as follows:
Based on the storm totals for those years and the current shorter, long term average of (11 – 6 – 2), along with a mix of forecast positive and negative factors, I have worked out the following seasonal hurricane outlook:
Total Storms: 9 – 11
Hurricanes: 4 – 5
Intense Hurricanes: 2 – 3
If conditions in the Atlantic do not show much improvement, I believe most of our formations will occur near 20N or above, and in the western Caribbean and closer to the U.S. East Coast. This may be where we see the strongest storms, based on already warm waters in the western Caribbean and the Gulf Stream.
Not that it means much, as it only takes ONE storm to create a catastrophe, these totals will be subject to change, as conditions warrant…as we saw during last season with the unexpected cooling of the Atlantic MDR.
Of course other factors will come into play, with one of the major players being the MJO, and how it evolves this summer / autumn.
Albeit our season begins June 01, 2014, I intend to begin issuance of my tropical product by mid month. Be advised however, I may be on and off, and may even be down for a week, as we are currently going through a move from our current residence.
Have a blessed week.
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST / SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
OFFICIAL SKYWARN SPOTTER (ADVANCED)