And I thought 2004 was a once in a century season!
Indeed, it has been a very active season and one apparently keyed into the MDO (Multi-Decadal Oscillation) of SSTs in the Atlantic... However, there are and were other factors in play. Less was the sub-Saharan soil moisture/rain fall, usually statistically correlated with a very active Cape Verdi season...
This year's phenomenal activity appears to have been more keyed into the SOI (Southern Oscillation index); where having that in concert with multi-seasonal warm SST anomaly in the Atlantic Basin gave circumstances this season a tremendous boost! There was very much less than the usual amount of shearing westerlies at mid and upper levels of the atmosphere, in the means, because the tropical Pacific SSTs were not as condusive as they could have been, in creating an excited westerly component over the SW Atlantic Basin. To the lay person, this may seem odd...that the SSTs of the tropical Pacific could exert and influence in the westerlies at low-latitudes over the Caribbean and adjacent areas, but such is the way of the atmosphere and the reasons are quite complex having to do with terrestrial physics.
Just for those who do not know: The MDO tends to be just that, "multi-decadal"....which, is code for happening over extended periods. The other key is "oscillation".....and, if you look back at the climatology of SSTs in the Atlantic Ocean, indeed, a periodicity of roughtly 25 years (that's rough) materializes in the data... It is no coincidence (it is currently theorized) that in over a 100 years worth of data, a flux in TC frequency coincides rather nicely with these warm periods. During such warmer departures from norm...should the other indices be also favorable, then POW! I am not honestly that certain what the sub-Saharan rain index was leading into this season but a vague memory of a report issued early on suggested it was below normal... That would have been a negative factor for contemporary thinking on the matter, but, since these other positives were so overwhelming, the rest was born. (Sub-Saharan rains are statistically correlated to stronger and more frequent tropical wave activity passing from Africa to the tropical/sub-tropical Atlantic Ocean).
This is all important to note because we are still embedded in the postive period of the MDO; meaning, more likely than not, positive Atlantic Basin SSTs will again be registerable in earnest, probably toward the end of next spring. All this activity did put a slight dent in the heat content, but when this season inevitably dies down there will definitely be enough vestigial warmth to ring off next summer with a higher than normal launching pad. SSTs will be quite hot, quite early, just as they were this season. So...from a purely cursory point of view, the table will be set for next season to be a big one!
The question: Who shows for dinner?? Will the SOI flip phases supporting a warm SST in the East Pacific, which would be a heavily weighted negative? Will sub-Saharan rains be greater, which would be supportive of stronger waves emerging off the west African Coast for perhaps a better expression of the "Cape Verde" season?? In other words, next season's frequency will depend most likely on these and other indices (not mention here for there relative smaller significance) that current scientific understanding only vaguely at best can predict their their modalities. The MDO is the most predominant and that is why it is of higher confidence... (We haven't even included Global Warming in this discussion - too argumentative for now...  )
Sufficed to say, however, with warmer than normal SSTs persisting next year (the favored state), we are in the very least probablistically on the higher than normal amount of activity aspect of the curve. Trust me: if the SOI is in LaNina and the SSTs remain warmer than normal - odds would favor much above normal. Time will tell...
Edited by typhoon_tip (Sun Oct 30 2005 12:31 PM)
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