When will the multi-decade active era that began in 1995 end?

[cycloneye]

The important part of why the North Atlantic has been very inactive in the past two years without having officially an El Nino is why the instability has been so low.That could answer in part the main question about if the 1995 and beyond active era is ending or has ended.

[Andrew92]

From another conversation I had, the ACE for this year and last year put together is less than 80 so far with little promise of meeting or exceeding that value if conditions remain as unfavorable in the Atlantic as they are.

There have been four other periods in the satellite era that saw combined ACE values for two consecutive years lower than 80. They were 1972-73, 1982-83, 1986-87, and 1993-94. In the two years immediately following each year, every single instance except 1988 saw a major hurricane hit the the United States (and 1988 was too close, with Gilbert striking just south of the border in Mexico). Some might point to 1984 as another major-free year for the US, but remember Diana did graze along the North Carolina coast while a Category 3, and I think briefly produced those strong winds onshore, ala Helene in 1958 and Emily in 1993. Furthermore, the only period where the Caribbean or Central America wasn't impacted at all by at least one major hurricane in at least one of the two years following these quiet spells was 1984-85.

I would say based on this, we need to pay attention to the next two hurricane seasons to see what happens. We can't say the active period is over because of 2013 and 2014. Then again, the 2000's was also an unusually active decade of activity in terms of major hurricanes hitting land throughout both the Atlantic and EPAC, rivaled only by the 1940's and 1950's.

-Andrew92

[Yellow Evan]

The important part of why the North Atlantic has been very inactive in the past two years without having officially an El Nino is why the instability has been so low.That could answer in part the main question about if the 1995 and beyond active era is ending or has ended.

Both TA (on the previous page) and Levi Cowan have suggested all the warm water in the subtropics decreases (-AMO/THC-like pattern) convection in the MDR, which leads to less storms. It also focuses MJO elsewhere.

[TheStormExpert]

Just because there has been two back-to-back inactive seasons all of the sudden doesn't mean that we are out of the active era just yet. "Wxman57" said before that it is very typical to have a few inactive seasons here and there during an active era, he also said that this active era sticks out from the rest for having the fewest inactive years which IMO should make these two inactive seasons a little more excusable right now. Of course in the next few years we should be able to get a better handle on what is going on, and if the active era is ending or continuing.

[Ptarmigan]

From another conversation I had, the ACE for this year and last year put together is less than 80 so far with little promise of meeting or exceeding that value if conditions remain as unfavorable in the Atlantic as they are.

There have been four other periods in the satellite era that saw combined ACE values for two consecutive years lower than 80. They were 1972-73, 1982-83, 1986-87, and 1993-94. In the two years immediately following each year, every single instance except 1988 saw a major hurricane hit the the United States (and 1988 was too close, with Gilbert striking just south of the border in Mexico). Some might point to 1984 as another major-free year for the US, but remember Diana did graze along the North Carolina coast while a Category 3, and I think briefly produced those strong winds onshore, ala Helene in 1958 and Emily in 1993. Furthermore, the only period where the Caribbean or Central America wasn't impacted at all by at least one major hurricane in at least one of the two years following these quiet spells was 1984-85.

I would say based on this, we need to pay attention to the next two hurricane seasons to see what happens. We can't say the active period is over because of 2013 and 2014. Then again, the 2000's was also an unusually active decade of activity in terms of major hurricanes hitting land throughout both the Atlantic and EPAC, rivaled only by the 1940's and 1950's.

-Andrew92

I consider an eyewall grazing as equal to eye making landfall.

[Ptarmigan]

One thing I have noticed; the ATL activity period correlates with the EPac inactivity. 1994 was the last season in a very active period in the EPac, and the last season in the inactive period in the ATL. And last year was an active season the east PACIFIC (despite most storms being weak) whereas it was inactive in the ATL. This year is also above-average in terms of storm number and ACE in the EPAC, and, below average in the ATL. So if next year's season in the ATL is inactive, and is opposite in the EPAC then the ATL active phase had concluded.

I kinda feel that is a myth.

Look at the 70s. And based on what I've gathered, the 30s and 20s were very active. It just happened to be the the AMO and PDO flipped at around the same time.

With that said, I imagine there's long been some correlation between EPAC and ATL activity. Because when the ATL is active, bye bye tropical waves for the EPAC. The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.[td100]

I ran a correlation between Atlantic and East Pacific activity. It is from 1971 to 2013. Here is what a I found.

ATL Total and EPAC Total
r = -0.32
p = 0.03

ATL Hurricane and EPAC Hurricane
r = -0.36
p = 0.02

ATL Major Hurricane and EPAC Major Hurricane
r = -0.37
p = 0.01

ATL ACE and EPAC ACE
r = -0.39
p = 0.01

ATL ACE/Storm and EPAC ACE/Storm
r = -0.09
p = 0.58

There is a negative correlation between ATL and EPAC. P-value below 0.05 is significant, which it is with the exception Atlantic and East Pacific ACE/Storm. The more active Atlantic is, the less active East Pacific is and vice versa.

[cycloneye]

The North Atlantic 2014 season was another average one with 8/6/2 so the question is will 2015 be the same or it will end the average to below average drought of the past 2 seasons. I agree with others that is too soon to proclaim with certainty that the active era since 1995 has ended but some factors have not been favorable in the past 2 years.If the 2015 season is another below to average season then the pot begins to stir a little bit more towards the question of this topic.Hey folks,good discussions going on here so keep it going.

[gigabite]

...I ran a correlation between Atlantic and East Pacific activity. It is from 1971 to 2013...

What is the alpha??? The p-value is the probability. What does the 2 sample T test look like?

[Ptarmigan]

...I ran a correlation between Atlantic and East Pacific activity. It is from 1971 to 2013...

What is the alpha??? The p-value is the probability. What does the 2 sample T test look like?

I used Paired Sample T-Test with PSPP.

Pair 0
ATL_Total - EPAC_Total
-4.12 Mean
7.46 Std. Deviation
1.14 Std. Error Mean
-6.41 Lower
-1.82 Upper
-3.62 t
42 df
0 Sig. (2-tailed)

Pair 1
ATL_Hurricane - EPAC_Hurricane
-2.74 Mean
4.83 Std. Deviation
0.74 Std. Error Mean
-4.23 Lower
-1.26 Upper
-3.73 t
42 df
0 Sig. (2-tailed)

Pair 2
ATL_Major_Hurricane - EPAC_Major
-1.79 Mean
3.45 Std. Deviation
0.53 Std. Error Mean
-2.85 Lower
-0.73 Upper
-3.4 t
42 df
0 Sig. (2-tailed)

Pair 3
ATL_ACE - EPAC_ACE
-25.67 Mean
97.78 Std. Deviation
14.91 Std. Error Mean
-55.77 Lower
4.42 Upper
-1.72 t
42 df
0.09 Sig. (2-tailed)

Pair 4
ATL_ACEStorm - EPAC_ACEStorm
0.21 Mean
4.16 Std. Deviation
0.63 Std. Error Mean
-1.07 Lower
1.49 Upper
0.33 t
42 df
0.75 Sig. (2-tailed)

[gigabite]

I used Paired Sample T-Test with PSPP.

Pair 0
ATL_Total - EPAC_Total
-4.12 Mean
7.46 Std. Deviation
1.14 Std. Error Mean
-6.41 Lower
-1.82 Upper
-3.62 t
42 df
0 Sig. (2-tailed)

Weird I get the same thing looking at just the Atlantic. It is like it is saying 60% of all years are normal and 40% are outliers.
Looks like the high side of the Atlantic cycle ran from 1997 to 2014. Judging by the Tropical Cyclone Count.
I have:
xbar = 15.13
Sx = 4.77
n = 30
minX = 9 at 1997 & 2014
maxX = 31 at 2005

[cycloneye]

I think "Active Era" is over except for a pop in 2016.

The above is from member gigabite that posted at the Expert forecasts for 2015 North Atlantic Hurricane Season thread

Two part question. According to that post,why the active era since 1995 ended and why a pop in 2016?

[gigabite]

I think "Active Era" is over except for a pop in 2016.

The above is from member gigabite that posted at the Expert forecasts for 2015 North Atlantic Hurricane Season thread

Two part question. According to that post,why the active era since 1995 ended and why a pop in 2016?

If you look at the above graphic it is clear that during the last 30 years there are two phases. I chose a 30 year range because it is the minimum standard for the Central Limit Theorem. It just happened that a cycle shaped like a cosine wave would be included. By definition a cosine wave would start at the mean go south of the mean cross the mean go north then close on the mean. To meet that definition, a cycle appears to have started in 1985 and ended in 2013 with a mid point at 1999.

As far as I can make out using celestial navigation as a mechanism to shake out a Atlantic cyclone count to avoid the climate/weather factors. Pressure is a likely candidate for the 38% anomaly ratio in the historical count. The Sun is the primary weather maker in the system. The distance to the Sun at aphelion varies from year to year. When the Sun is farther away the hurricane count increases when it is closer the count decreases. 2016 is the next time the Earth swings away from the Sun, but more often than not the Earth is closer to the Sun in the summer for the next 6 years.

A third factor is the oscillation of the length of the major axis of the Earths orbit. For example 2005 the aphelion distance was 1 standard deviation larger but the sum of aphelion and perihelion distances was 3.5 standard deviations larger. The sum of aphelion and perihelion in 2016 is 3.25 standard deviations larger.

[Yellow Evan]

1995 is widely considered the start of the active era in the ATL basin due to the AMO flip.

[gigabite]

Thanks for the enlightenment. My case just deals with raw Tropical Cyclone Count. The P for the 95 start is 12/20 where the P for the 99 start is 11/15. I have trouble relating chaos to chaos as in AMO to TCD. I want my universe to be predictable. The current methodologies are getting better at forecasting the instantaneous without explaining music.

[cycloneye]

This debate about the question that this topic has has returned as NOAA in their outlook of May talk about it.

the atmospheric conditions expected during ASO 2015 (i.e. stronger vertical wind shear, enhanced sinking motion, increased atmospheric stability) contrast with these active-era patterns. Following two relatively quiet hurricane seasons (2013 and 2014 (Bell et al. 2014, 2015), along with the current projection of Atlantic SST anomalies onto the cold phase of the AMO, debate has surfaced as to whether we are still in this high-activity era.

[Andrew92]

This debate about the question that this topic has has returned as NOAA in their outlook of May talk about it.

the atmospheric conditions expected during ASO 2015 (i.e. stronger vertical wind shear, enhanced sinking motion, increased atmospheric stability) contrast with these active-era patterns. Following two relatively quiet hurricane seasons (2013 and 2014 (Bell et al. 2014, 2015), along with the current projection of Atlantic SST anomalies onto the cold phase of the AMO, debate has surfaced as to whether we are still in this high-activity era.

Let's remember this is an El Nino year, so one should expect a quiet Atlantic season, even in an active period.

Let's also pretend El Nino is gone by this time next year. I have a gut feeling if that is the case, some will be saying how active next year could be. And then there is the theory I have, the second-year-after theory, where a hurricane with a pressure below 965 mb (on par with Category 3's or higher) has hit the US in every single instance two seasons after the most recent traditional El Nino in the satellite era. Assuming this event lasts only through this year, I think by the end of 2017 we will have a much better idea if the active period is over or not.

-Andrew92

[xtyphooncyclonex]

2013 was not an El Niño year (near La Niña at times) and yet was one of the least active seasons in terms of ACE. That year was among the weakest seasons on record. The Pacific inactivity period has something to do with the Atlantic activity period. Same does with the opposite. Now the Pacific had a crazy active season, not seen since 1992 and this year is expected to be the same. Also the PDO shifted to crazy positive values. In the ePac, 2009 did not have a crazy active season (but crazy storms) despite being an El Niño and below avg ACE, yet 2014 had a weaker Niño yet was a huge ACE and named storm count season. Crazy active season going on in 2015 over the Pacific and AMO values are low at the same time PDO shifted to positive

[xtyphooncyclonex]

The North Atlantic 2014 season was another average one with 8/6/2 so the question is will 2015 be the same or it will end the average to below average drought of the past 2 seasons. I agree with others that is too soon to proclaim with certainty that the active era since 1995 has ended but some factors have not been favorable in the past 2 years.If the 2015 season is another below to average season then the pot begins to stir a little bit more towards the question of this topic.Hey folks,good discussions going on here so keep it going.

2014 was a BELOW AVERAGE SEASON, and 2015 too is expected to be one too

8 storms is far from the normal

[Andrew92]

Another thing that occasionally happens, looking at history, as that even in non-El Nino years, if it's been a while since the last El Nino event, conditions eventually get rather unfavorable for big hurricanes in the Atlantic. 2013 is the most recent good example of this, but not the only one. Another quiet, non-El Nino year that immediately comes to mind is 1962, when it had been four years since the last El Nino. I also believe we were in an active period during that time, am I correct?

Or another front, sometimes those types of years favor quantity, but little quality. Think 1981 and 1990, for instance. 1981 had 12 storms (one being subtropical) and 1990 had 14. Yet, few of the storms in those two years got particularly strong for particularly long periods of time. I question Floyd from 1981's status as a Category 3 if its minimum pressure was 975 mb, as it looked like an average-sized hurricane...this could suggest a high-end Category 1 or a low-end Category 2 instead, but re-analysis will tell us in a few years or so. Only two other majors occurred that year, and one major very briefly occurred in 1990. (I don't question the intensities of those majors as much as Floyd in 1981 though.) The last El Nino event before each of these years was in 1977 and 1987, respectively, a fairly long gap between El Nino events.

It kind of begs the question, is there an irony that Atlantic hurricanes need El Nino every now and then in order to have more fuel pumped for when those events subside? Is the energy that hurricanes need sapped when El Nino doesn't take place often?

-Andrew92

[Hammy]

8 storms is far from the normal

I would say last year was average, given the ACE, because 2013 with 14 storms but being so weak (and only two Cat 1 hurricanes) can't really be considered above average.

As far as this year, all indications are that it will probably be 2013-ish as far as the ACE goes, but with fewer storms (probably stronger).
And given the conditions, I wouldn't be surprised to see no storms east of 50-55W. Whether the active period has ended or not though, the last one had several year dips in the AMO with weaker storms/weaker seasons, and as several have pointed out here, the current active cycle stands out by not having any of those, which may lead to a false sense that it's over with the dip that we're in.