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Active Early ATL & Active Season Overall? Maybe!
      #96367 - Wed Jun 15 2016 12:08 AM

There May in Fact Be a Correlation Between Active Early Season ATL & Active Overall

We have had an active start to the 2016 Atlantic Hurricane Season. As a result, many have asked whether an early start to an Atlantic hurricane season can be indicative of a season overall, with the press, and indeed, tropical cyclone experts addressing this, but I would argue, answering the wrong question (and so, with an answer that does not do the actual question justice).

Instead of addressing the question of whether or not an active early season can give us clues as to the rest of a season, many experts and media personalities have all but unequivocally shown how years with names that start prior to the official start of a season have no statistically noticeable change up or down in final numbers.

Maybe the question needs to be rephrased, so that it accurately reflects what has happened thus far in 2016. I submit that the correct question to ask is, "What can we learn, if anything, about Atlantic basin hurricane seasons that have had two nameable storms before June 15?"

Please note that I have not asked for three. Why? For one, because I'll give you that Alex could very well be an out-of-season fluke, as we have indeed seen many times before, with the end result being no clue one way or another on how the actual official season is going to wind up. Also, there wouldn't be any other seasons but 2016! So, let's ignore Alex, for now, and just look at Atlantic basin years with two named/nameable (storms or better) that developed before June 15.

Not satisfied that the question was being phrased accurately, or the answers given were not delving deep enough, or both, I set out to learn more, using the best, most reliable data formally available to us at this time.

Right away it becomes apparent that there have been very few seasons on record with two named/nameable cyclones by June 15th. One year that really jumps out from long, long ago, and has been talked about recently in the press as the one season that 2016 just beat out for earliest named 3rd storm, was 1887. 1887 saw two Tropical Storms in May and one just before the middle of June. Season Total: 19/11/2 (3rd Name: THREE existed June 11-June 14, becoming a storm early early on the 12th).

It is crystal clear that even without the aid of modern day satellites, the record shows 1887 to have been a banner year for nameable cyclones in the ATL. As its Wikipedia entry notes,"The 1887 Atlantic hurricane season was the third most active Atlantic hurricane season on record, tying with the 1995, 2010, 2011, and the 2012 seasons for third most number of storms." But even with that very respectable count, several were still easily missed that year.

Unfortunately, all these early seasons show good reasons why we should probably not look so far back for reasonably reliable indicators. So, sorry 1887 and others, we'll just look at the Satellite Era (Since 1961).

So we're going to be looking for seasons since 1961 (55 seasons total up through 2015), that produced two or more nameable cyclones prior to June 15th.

For this project, even though the Satellite Era is much more reliable than before, the numbers also clearly show that it was still many, many years into it that the science and data became good enough to differentiate Depressions from weaker and/or short-lived Storms. Consequently, we will be comparing not Names+Hurricanes+Majors, but rather Sub and/or Tropical Cyclones+Hurricanes+Majors, using a standardization formula that I will describe below.

Please note, for discussion's sake, I use "TCs" generically, to include sub-tropical as well as tropical cyclones.

In the 1960s, 70s and 80s, far lower percentages of TCs were ever classified as more than a Depression. It is believed by many, reasonably, that this was largely owing to a lack of adequate data collection, and lower deterministic skill, and likely also so with Named storms that went on to be recognized as Hurricanes, and from there, a few Majors.

Since 2000 we have had 270 TCs, of which 241 became officiated as Storms, for an 89% Storm to TC Ratio. So, in order to keep things normalized, I am only counting TCs, Hurricanes and Majors for all years in question since 1961, but will apply an approximated Named/Hur/Major to each year, and then compare this to an 'average' season, by designating 89% of all TCs as Storms for the seasons through 1981.

And looking at the ratio of Hurricanes to Depressions for these early Satellite Era decades also runs very low, I have further standardized the Hurricane numbers for these seasons on a ratio that matches the average of the years 2006-2015, as these seasons avoid the record hyperactive 2005, yet include seasons that were well below average, average, and well above average, including both Positive (and possibly for the past three seasons, Negative, mild phase - or pause) of the AMO.

From 2006-2015 we had 140 Storms of which 63 went on to become hurricanes of any category, for a Hurricane to Storm ratio of 45%. The ratio of 45% is thus applied to the "Standardized Names" for the seasons to 1981, for a "Standardized Hurricanes" number.

"Climo" As I have done with applying modern-day standardization to the Names and Hurricane numbers above, I will be using Avg Climo Numbers of years 2006-2015. Again, the seasons from 2006-2015 avoid the record hyperactive 2005 season, yet include seasons that were well below average, average and well above average, including both the active phase (and possibly for the past three seasons inactive phase - or pause) of the AMO. Climatology from 2006-2015: Names:14 Hurricanes: 6 Majors: 2.5

1967: TD1 June 10-12, TD2 June 10-13, TD3 June 14-18.
TCs: 26, HURs: 5, MAJs: 1 Memorables: Cat 5 Beulah (Standardized 23N/10H/1M)
Result vs. Climo: Names: Much Higher, Hurs: Much Higher, Majors: Below

1969: TD1 May 29-June2, TD2 May 29-30, TD3 June 7-9, TD4 June 12-15
TCs: 29, HURs: 12, MAJs: 5 Memorables: Cat 5 Camille, Cat 3 Francelia, Cat 3 Gerda (Standardized 26N/12H/5M)
Result vs. Climo: Names: Much Higher, Hurs: Much Higher, Majors: Much Higher

1972: TD1 May 23-29, TD2 June 14-23
TCs: 19, HURs: 3, MAJs: 0 Memorables: NONE (Standardized: 17N/8H/0M)
Result vs. Climo: Names: Higher, Hurs: Higher, Majors: Well Below

1973 TD1 Apr 18-21, TD2 May 2-5
TCs: 17, HURs: 4, MAJs: 1 Memorables: Cat 1 Brenda (Standardized: 15N/7H/1M)
Result vs. Climo: Names: Avg, Hurs: Average, Majors: Below

1976: TD1 May 21-25, TD2 June 7-9, TD3 June 11-12
TCs: 21, HURs: 6, MAJs: 2 Memorables: NONE (Standardzied: 19N/9H/2M)
Result vs. Climo: Names: Much Higher, Hurs: Higher, Majors: Avg

1981: TD1 Apr 6-7, TD2 Apr 19-21, TD3 May 6-9, TD4 June 3-5
TCs: 22, HURs: 7, MAJs: 3, Memorables: NONE (Standardized: 20N/9H/3M)
Resul vs. Climo: Names: Much Higher, Hurs: Much Higher, Majors: Avg

2003: TD1 Apr 18-27, TD2 June 11
TCs: 21, HURs: 7, MAJs: 3, Memorables: Cat 1 Claudette, Cat 4 Fabian, Cat 5 Isabel, Cat 2 Juan (Actual: 16N/7H/3M)
Result vs. Climo: Names: Higher, Hurs: Avg, Majors: Avg

2007: TD1 May 9-14, TD2 May 31-June 5
TCs: 17, HURs: 6, MAJs: 2, Memorables: Cat 5 Dean, TS Erin, Cat 5 Felix, Cat 1 Lorenzo, Cat 1 Noel, TS Olga (Actual: 15N/6H/2M)
Result vs. Climo: Names: Avg, Hurs: Avg, Majors: Avg

2012: TD1 May 19-23, TD2 May 25-June 2
TCs: 19, HURs: 10, MAJs: 2, Memorables: Cat 1 Isaac, Cat 3 Sandy (Actual: 19N/10H/2M)
Result vs. Climo: Names: Much Higher, Hurs: Much Higher, Majors: Avg

Avg of The Standardized/Actual Active Early Seasons Numbers (Total of 9 Seasons) Names: 19 (170/9), Hurricanes: 8.5 (78/9), Majors: 2 (19/9), versus Climatology baseline 2006-2015: Names:14 Hurricanes: 6 Majors: 2.5

From these numbers, it is also apparent that well above average early season activity can occur regardless of AMO phase, as might be expected, considering that the seedling of pre and early season tropical cyclogenesis is often frontal.

"The AMO phase was classified as being positive from 1878–1899, 1926–1969 and 1995–2012, and negative from 1900–1925 and 1970–1994." ~ Klotzbach and Gray

All comments, critiques, additional thoughts, data, questions, etc. gladly accepted!

Let's figure this out together!

This entry was originally posted in my Wunderblog

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