Remember how the experts were calling for another active season at the start of June? Just about everything seemed to be in place: a forecast for normal-to-warm Atlantic waters accompanied by relatively low surface pressures and no El Niño to enhance mid-level shearing winds and disrupt development. Then, add in the fact the Atlantic Basin has just been busy in recent years.
Since 1995, annual storm counts have averaged roughly 25 percent above the longer-term norm, with 11 of the past 18 seasons (back to 1995) having 15 or more 'named' systems. To top it off, the basin saw back-to-back-to-back seasons (2010-2012) with 19 'named' storms, three consecutive years that tied as the third most active on record!
Yet, here we are into the first week of September with seven Atlantic tropical storms so far, but no hurricanes. Yes, it looks like the pre-season consensus among various forecast groups, suggesting something on the order of 15-17 'named' storms is in serious jeopardy ... not that anyone is complaining!
We could come up with a laundry list of reasons why various storms this season have failed to fully develop. But for the season as a whole thus far, two key factors have been unexpectedly persistent: mid-level shearing winds (in spite of the absence of El Niño) and mid-level dry air across much of the tropical latitudes. Both can be effective hurricane inhibitors.
But, let's not cancel the rest of the season just yet. Statistics tell us that, on average, roughly 60 percent of the Atlantic Basin's activity occurs after September 1. In other words, the Atlantic's tropical action tends to be slightly tilted towards the second half of the season. If the second half of the 2013 season turns out to be "just average," we could see another half-dozen 'named' storms before Christmas.
Still, we set a tropical record of sorts on September 5 and we may see another record broken over the coming days in this "quieter than expected" season.
You've probably already heard it:
The last time the Atlantic Basin made it past September 1 without a hurricane was during the 2002 season. Ironically, the first hurricane in 2001 was also in September, a rather odd back-to-back occurrence. In fact, since 1960, only this current season (2013), 2002, 2001 and 1984 made it through the first week of September without an Atlantic hurricane.
First Hurricanes in September:
1984: Diana on September 10
2001: Erin on September 8
2002: Gustav on September 11
Note that 2002's Gustav reached hurricane strength on September 11, the latest-forming first hurricane in more than 50 years.
We said 'goodbye' to 2013's Gabrielle Thursday night, which means we will reach the eighth 'named' storm (Humberto), at least, before declaring a hurricane in the basin during 2013. That is the 'deepest' the basin has gone into an annual 'names' list since the onset of the "satellite era" (roughly the last 40+ years) - a new record. (In fact, it's the farthest into any list since 1950, the first year of alphabetical naming of Atlantic tropical systems.)
And with just five days to go and nothing imminent on the tropical horizon, we are posed to go past 2002's record of September 11 for the "latest" first hurricane (since operational satellite tracking) before declaring the first "Category 1" of the 2013 season - that would be record No. 2.
Admittedly, if we look farther back in the Atlantic tropical records, we find that 2002's Gustav is not the "latest" first hurricane ever for the basin. For example, according to NHC records, the first hurricane of the 1941 season did not appear until September 21. And those same official records indicate no hurricanes at all during the 1907 and 1914 seasons! But "official" or not, experts agree that tropical tracking prior to the availability of satellite imagery was somewhat suspect, especially for storms far out over the open Atlantic.
If we limit our review to the period when reliable satellite coverage has been available and our confidence of tropical tracking is high, then we already have one "first ever" guaranteed this season and could see a second record (albeit somewhat trivial) established over the next several days.
And, about those pre-season forecasts? They simply remind us of what we already knew: we still have an awful lot to learn about tropical weather!
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