A theory on the tropics

[MiamiensisWx]

This may be speculation, but I think it is quite interesting.

I actually believe some people have misninterpreted the possible effects of climate change (GW) on tropical cyclones. I have been suspecting (for a long time) that GW might lead to reduced numbers of hurricane days in the Northern Hemisphere (all tropical basins from Atlantic to EPAC/WPAC). Obviously, there are other factors, but I'm starting to wonder if we are slowly observing an average (mean) downward trend in terms of hurricane days in the Atlantic basin. This trend probably began prior to 2003, but the influence has been slight (it's a gradual process). It makes sense, especially because of very inactive years in the EPAC and WPAC (i.e. 2006 and 2007). Additionally, I wonder if the +AMO is becoming more negative, thus reducing hurricane days in the Atlantic basin. We need a larger data sample, but a combination of GW (natural, anthropogenic, or both) and other factors (i.e. the AMO) could reduce the number of hurricane days in the Atlantic, EPAC, and WPAC over the next several decades.

What do you think?

[terstorm1012]

I'm intrigued.

While there's no exact way to determine hurricane days from years where we can't possibly observe, there are a number of studies that I've come across in the last year or so that indicate that there were more intense storms during the time when the Earth was cooler during the little Ice Age, based on reconstructed proxies such as sediment cores, and historical records (in the case of Guangdong Province, China.) Of course as I and even the IPCC states, there's a lack of real long term records (China and Japan would have the best in the West Pac).

Do you have more to base your theory on? I think it's a start of a thesis if you're in school.

[Cyclenall]

This may be speculation, but I think it is quite interesting.

I actually believe some people have misninterpreted the possible effects of climate change (GW) on tropical cyclones. I have been suspecting (for a long time) that GW might lead to reduced numbers of hurricane days in the Northern Hemisphere (all tropical basins from Atlantic to EPAC/WPAC). Obviously, there are other factors, but I'm starting to wonder if we are slowly observing an average (mean) downward trend in terms of hurricane days in the Atlantic basin. This trend probably began prior to 2003, but the influence has been slight (it's a gradual process). It makes sense, especially because of very inactive years in the EPAC and WPAC (i.e. 2006 and 2007). Additionally, I wonder if the +AMO is becoming more negative, thus reducing hurricane days in the Atlantic basin. We need a larger data sample, but a combination of GW (natural, anthropogenic, or both) and other factors (i.e. the AMO) could reduce the number of hurricane days in the Atlantic, EPAC, and WPAC over the next several decades.

What do you think?

Did you come up with this idea before or after you read that article about how GW could reduce the number of storms because of higher wind shear? Or have you never read that article (I'm pretty sure you would know about it).

We have to wait longer to get an idea of this to see if there is any trends reguarding this.

[MiamiensisWx]

Currently, I'm attempting to research additional data. I was looking for information on the current AMO in linear trends (i.e. line graphs). I'm a high school student. I formulated this theory prior to the article mentioned by Cyclenall (which I have read), although it certainly piqued my interest. The feedback of the Pacific likely plays a role in terms of favorability for Atlantic tropical cyclogenesis. EPAC convection leads to lower background pressures in the Caribbean, with a greater tendency for subtropical highs during La Nina years. Climatologically, the lack of October activity in the Atlantic during 2007 has been quite anomalous; Noel is the first NS to form during this month. On average, activity ramps up later during many Nina years, thus leading to a peak in September-October and late season formation into November-December. The anomalously strong subtropical TUTT cells during September 2007 have been intriguing, too. On a minor scale, warm SSTA off Ecuador (which enhances EPAC instability = convection) may support higher shear values over the Caribbean (displaced subtropical high + UL outflow from EPAC convection cuts off adjacent systems), but other factors usually override this factor in active seasons. I need to do more research on the other factors, but I posted my original persistent preliminary thoughts for brevity. I would appreciate additional input. Thanks.

[caneman]

Of course it may not have anything at all to do with Global Warming because there may not be any such thing as GW and the next 5-10 may bear that out. So, it in fact may just be the cyclical nature of the Tropics and the environment.

[MGC]

Following the record hurricane season in 1933 (I think that year), the next two season saw a trend towards the long term average, with a notable reduction of tropical cyclones developing in the Atlantic basin. The same thing has happened after the record hurricane season in 2005, numbers have trended towards the long term average. I don't think that GW was the cause of the 1933 or 2005 seasons, just a ramdom occurance that conditions became just right for TC formation and development. We may not see another season like 2005 for many years. Funny but the GW crowd has been mighty quiet the past couple of seasons considering their chest pounding after the 2005 season that the world was coming to an end. But, I'm sure they will find a reason for the less than expected TC activity and intergrate it into the GW scare models........MGC

[StormWarning1]

Currently, I'm attempting to research additional data. I was looking for information on the current AMO in linear trends (i.e. line graphs). I'm a high school student. I formulated this theory prior to the article mentioned by Cyclenall (which I have read), although it certainly piqued my interest. The feedback of the Pacific likely plays a role in terms of favorability for Atlantic tropical cyclogenesis. EPAC convection leads to lower background pressures in the Caribbean, with a greater tendency for subtropical highs during La Nina years. Climatologically, the lack of October activity in the Atlantic during 2007 has been quite anomalous; Noel is the first NS to form during this month. On average, activity ramps up later during many Nina years, thus leading to a peak in September-October and late season formation into November-December. The anomalously strong subtropical TUTT cells during September 2007 have been intriguing, too. On a minor scale, warm SSTA off Ecuador (which enhances EPAC instability = convection) may support higher shear values over the Caribbean (displaced subtropical high + UL outflow from EPAC convection cuts off adjacent systems), but other factors usually override this factor in active seasons. I need to do more research on the other factors, but I posted my original persistent preliminary thoughts for brevity. I would appreciate additional input. Thanks.

I would go to the 1931 edition of the Monthly Weather Review and study the 1931 tropical cyclone activity for the North Atlantic.
Here is a link that takes you to the NHC site, scroll down about midway for the link to the annual summaries 1872 to 2002.
http://www.nhc.noaa.gov/pastall.shtml
The 1931 season is very similar to 2007, at least so far. No hurricanes Above 20N and East of 94W. Perhaps one of those West Gulf tropical storms was briefly a hurricane, like this years Lorenzo. It is also likely there were some short lived storms in the far North Atlantic or Eastern Atlantic that went undetected. The two hurricanes of 1931 took westward tracks into the Yucatan, one hitting exactly where Dean did this year.

[Frank2]

Just a thought here, but, perhaps this is the flip-side of the "too cold (too dry) for snow" theory - Global Warming could also lead to "too hot (too dry) for rain"...

It's a well known fact that moisture is most found in temperate or tropical (not desert-hot, just warm and damp) climates - Arctic or Desert climates being the driest...

[terstorm1012]

Currently, I'm attempting to research additional data. I was looking for information on the current AMO in linear trends (i.e. line graphs). I'm a high school student. I formulated this theory prior to the article mentioned by Cyclenall (which I have read), although it certainly piqued my interest. The feedback of the Pacific likely plays a role in terms of favorability for Atlantic tropical cyclogenesis. EPAC convection leads to lower background pressures in the Caribbean, with a greater tendency for subtropical highs during La Nina years. Climatologically, the lack of October activity in the Atlantic during 2007 has been quite anomalous; Noel is the first NS to form during this month. On average, activity ramps up later during many Nina years, thus leading to a peak in September-October and late season formation into November-December. The anomalously strong subtropical TUTT cells during September 2007 have been intriguing, too. On a minor scale, warm SSTA off Ecuador (which enhances EPAC instability = convection) may support higher shear values over the Caribbean (displaced subtropical high + UL outflow from EPAC convection cuts off adjacent systems), but other factors usually override this factor in active seasons. I need to do more research on the other factors, but I posted my original persistent preliminary thoughts for brevity. I would appreciate additional input. Thanks.

If you have access to an academic library you might want to look for this paper: Donnelly, J.P., and J.D. Woodruff. 2007. Intense hurricane activity over the past 5,000 years controlled by El Niño and the West African monsoon. Nature, 447, 465-468.

[Ptarmigan]

If you have access to an academic library you might want to look for this paper: Donnelly, J.P., and J.D. Woodruff. 2007. Intense hurricane activity over the past 5,000 years controlled by El Niño and the West African monsoon. Nature, 447, 465-468.

Any data for West African monsoon. I would be interested in it.

[Squarethecircle]

Interestingly enough, that's exactly what GW, with shear, less clouds forming, and high heat content should be doing. Whether or not that's true, there's still a lot of this that we really don't understand that well, but the 1930s seasons leads to an interesting point... a similar thing happened in 1969, with 1971 being very similar to 2007 in that it had an average or below average number of hurricanes, but an above average number of named storms.

[Tampa Bay Hurricane]

I agree with you Miamiwx...I think that is what is happening.

[Downdraft]

Of course it may not have anything at all to do with Global Warming because there may not be any such thing as GW and the next 5-10 may bear that out. So, it in fact may just be the cyclical nature of the Tropics and the environment.

I don't believe that there is any debate about whether GW exists I believe what is in debate is how much of it can be attributed to human society. I don't see how any rationale person can debate the earth is warming based upon the evidence.

[Derek Ortt]

I have speculated here that in a GW world, we'd see fewer overall cyclones due to conditions being less favorable for genesis as a whole. We would also see more intense hurricanes, but they would remain in the tropics as the need to transport heat from the tropics to the poles would be diminished.


This year's WPAC season blew that hypothesis to kingdom kong.

Maybe this year was caused by a few intense WPAC typhoons moving into the high latitudes, which efficiently redistributed enough heat form the tropics to the poles to cause a reduction in overall activity. This is merely speculation on my part

[Squarethecircle]

I have speculated here that in a GW world, we'd see fewer overall cyclones due to conditions being less favorable for genesis as a whole. We would also see more intense hurricanes, but they would remain in the tropics as the need to transport heat from the tropics to the poles would be diminished.


This year's WPAC season blew that hypothesis to kingdom kong.

Maybe this year was caused by a few intense WPAC typhoons moving into the high latitudes, which efficiently redistributed enough heat form the tropics to the poles to cause a reduction in overall activity. This is merely speculation on my part

Of course, not all years can be like one that probably won't happen until the full effects of GW, whatever they may be, take effect in a few decades, and that is actually fairly interesting... How much energy would be required to transport heat from the tropics to the subtropic without ocean currents (throughout the course of the year)?

We might have to wait a few years to see whether the extent of GW is enough to eliminate the threat of storms (for at least a few decades, before the ice age kicks in), or whether it would simply produce an enhanced version of the 2007 Atlantic season. The overall threat will most certainly be reduced, especially to the CONUS.

[caneman]

Of course it may not have anything at all to do with Global Warming because there may not be any such thing as GW and the next 5-10 may bear that out. So, it in fact may just be the cyclical nature of the Tropics and the environment.

I don't believe that there is any debate about whether GW exists I believe what is in debate is how much of it can be attributed to human society. I don't see how any rationale person can debate the earth is warming based upon the evidence.

I would agree with you. The Earth is warming just as it has for thousands of years only to be followed by significant cooling. The argument is more about the immediate doom and gloom scare tactics. The next 10 years will tell the tale. There will be a lot of red faces when we enter into another cooling faze. IMHO.

[Sanibel]

Wrong about a down trending AMO. 2007 saw a large number of systems try to form. It was conditions outside the AMO parameters that caused them not to develop. If we had 2007 with the same background conditions as 2005 we would have seen a large number of strong systems.

[Squarethecircle]

The problem was that the conditions were what they were. A lot of the systems formed very close to land, even more could not sustain convection or did not have the energy to keep them intact, and more still were ripped apart by wind-shear. The world-wide inactivity (discounting the North Indian basin), however, could be an anomaly, if similar events to those that have happened this year occur, then maybe a conclusion could be drawn. Also, it is interesting to note that, for most of the recent storms (past three years), the ACE has been closer to average, while a year before that, we had Ivan and Isabel and others.