Atlantic hurricane season

For all global hurricane basins, there are 'best track' data files extending back to year 1945. Thus it would be possible to calculate ACE over this longer period.

No one has done that because in pre-satellite era, some storms at sea might have gone undetected. If so, ACE would be underestimated (early), giving a misleading appearance of later increase. No one wishes to mislead.

Well, almost no one

 

The Maue (weatherbell) site shows graphs of frequency and ACE. I don't think it is a massive problem to mix them up.

They both show substantial variation through time. Same thing as saying there are periods of decrease. There are. There are also periods of increase. If one approaches these graphs with an expectation of seeing a decrease, well, that is what one might see. It is a problem, but can be cured.

Over Maue's entire analyses, there are no significant trends. The very small increase in global ACE is not significant.

The graph @18 does suggest an increase in major hurricane numbers. But Maue does not present that (global) data file, so I cannot test. Thus, cannot claim. There have been publications on the subject, going further back in time than 1970. Which is probably OK because we'd not likely miss a 'major'.

+++

We started here on the North Atlantic itself, not global. N Atl continues its several years of unusually low activity, and I don't think anybody has a handle on that. In this and several other ways ocean dynamics are not well understood. Until that improves hurricane (or climate) modeling will simply remain unsatisfying. To me at least

However, data we have, and analyses we can do, those are fine. If a misinterpretation arises, fix it. No big deal.

 

"You don't see?" @25.

Sure I do, I see them all. With data to spreadsheet it is no trouble to evaluate each one. The numbers are R2 for each segment:



This is not the only 'pattern' of segments one could choose, and the positions of the line segments are not completely accurate (the R^2 values are the important part). But what should be obvious is that high variation (such as here) will very often yield segments that are significant by regression. I don't like the reds or greens better. Like 'em all.

What we could do (constructively) is use this amount of variation to determine how many years of data would be required to detect a significant trend. That is a different formula, and not for today. But that itself depends on the variation remaining constant in the future. Might, might not eh?

In a way it resembles arguing no significant +T (which only works if you start in 1998).

 

Tidbit@31

This is well worth mentioning as it uses proxies for hurricane frequencies:

Hurricane frequency dropped during 17th century ‘Little Ice Age’ | Science News

 

Much effort has been put into N Atl hurricane records. HURDAT starts in 1851, and it may have missed some storms in early times. Other hurricane basins are more sketchy in early times; besides this is a N Atl thread.

Link here:
Hurricane Research Division Data Policy
“We ask that a proper acknowledgement to the "NOAA Hurricane Research Division of AOML" accompany the use of these data in any publications or presentations”

That dataset, with each storm every 6 hours, is too detailed for this purpose. Wunderground has helpfully simplified it to hurricanes per year:
Hurricane Archive | Weather Underground

Sunspot numbers per year data as mentioned previously. To ‘stack the deck’ favorably I choose 11-year smoothing. Here is the graph:



One can see periods when they vary together and others oppositely. If you wanted low sunspot numbers to cause few hurricanes, you would only look at the former. Maue’s global hurricane frequency does not consistently follow SSN either, but it is rather short for such a purpose.

 

SNN -> SSN in the title. How embarrassing.

BTW there have been publications discussing an increase in N Atl hurricane frequency since 1851. Annual data do have a positive regression, but R^2 - 0.049. Which ain't much.

 

Atlantic Multidecadal Oscillation (AMO) is well worth considering in this context. By those who defined it, it is considered to be driven up by greenhouse gases, down by aerosols, and with a 65-70 yr physical ocean oscillation. The last of course is a very common theme

As AMO is derived from sea-surface temperatures, it is not appropriate to say "AMO has cooled sea surface temps". But we need not dwell on that

Since 1856, annual AMO values relate a bit better to N Atl hurricane frequency (R^2 = 0.19). For the last full year of data (2015) AMO was less than its highest value (in 2010) but still high compared to all years since 1856.

There is not yet a good way to predict next year's (next decade's) AMO. I'd not doubt that 'iceagenow' (etc.) expect it to decrease substantially. But neither am I compelled to agree.

 

If anyone cares to explore AMO, data are here:

ESRL : PSD : Download Climate Timeseries: AMO SST

But you gotta keep your wits about you. Records are presented as 'detrended' and 'not detrended'. What does this mean? Sea-surface termperatures have increased throughout the period of record. Detrended removes that secular trend.

CO2 has also increased since 1856. So for example. if you compare [CO2] to detrended AMO, you will get diddly.

This, for example, is detrended:
File:Amo timeseries 1856-present.svg - Wikipedia, the free encyclopedia

 

Tropical storm Karl (mid Atlantic) has a chance of further strengthening, and of hitting US coast. Not as a 'major' though. More Hermine-sized.

 

Hurricane Matthew (as a 1 or 2) has a lock on Cuba. Whether it can get interestingly close to Florida (etc. north) depends on how sharp a right-hand turn it can make. Recurving is a normal hurricane thing, but right-angle turns are not. An interesting test for meso-scale models.

Tropical Cyclone Intensity and Track Forecasts