NOAA also forecasts a high hurricane activity for the remainder of the season, and time will show if this season will match the 2004 in terms
of number of tropical cyclones.
I believe the jury is still out on the question
of the number of tropical cyclones because the IPCC's assessment has so far not included studies on the relationship between the number of tropical cyclones and the area of high sea surface temperature, such as the analysis shown in Fig 2 (1).
Not exact matches
Diverging from other computer models, a new study suggests that efforts to clean the air in Asia may boost the
number of tropical cyclones worldwide
Looking at data from 1855 through 2005, Webster and Holland found that the total
number of tropical cyclones per year doubled in that time, from an average
of six at the beginning
of last century to 14 over the past decade.
This is the greatest
number of U.S. direct fatalities related to a
tropical cyclone outside
of the southern states since Hurricane Agnes in 1972.
The earlier years
of that time period had a high
number of tropical cyclone landfall events, while the latter years experienced relatively few.
Even if the
number of tropical cyclones that form in the Atlantic increases, that doesn't guarantee that the
number making landfall will also rise.
But no matter what the future brings, one thing is clear — the regularity and
number of tropical cyclones making landfall will continue to be vital.
The
number of tropical cyclones was more than the eight that occurred during the 2014 season.
According to the most recent Intergovernmental Panel on Climate Change report, the wind speed and rainfall rates in
tropical cyclones are projected to increase during the 21st century, even while the total
number of tropical cyclones remains nearly steady, or even decreases.
I have also witnessed a
number of natural disasters: earthquakes in India and the US, a tornado in Michigan, floods in Texas, as well as a tsunami and
tropical cyclones in India.
As the climate changes,
tropical cyclones are expected to produce more rain and the frequency
of the highest intensity storms is projected to increase even though the overall
number of storms may remain unchanged or perhaps even decrease.
This debate (as carefully outlined by Curry et al recently) revolves around a
number of elements — whether the hurricane (or
tropical cyclone) data show any significant variations, what those variations are linked to, and whether our understanding
of the physics
of tropical storms is sufficient to explain those links.
Overall, there appears to have been a substantial 100 - year trend leading to related increases
of over 0.78 C in SST and over 100 % in
tropical cyclone and hurricane
numbers.
Of course, since hurricanes and tropical storms are all just degrees of intensity of the same type of storm — tropical cyclones — and since there are a very limited number of data points of one limits the data to hurricanes, it makes sense to include tropical storm
Of course, since hurricanes and
tropical storms are all just degrees
of intensity of the same type of storm — tropical cyclones — and since there are a very limited number of data points of one limits the data to hurricanes, it makes sense to include tropical storm
of intensity
of the same type of storm — tropical cyclones — and since there are a very limited number of data points of one limits the data to hurricanes, it makes sense to include tropical storm
of the same type
of storm — tropical cyclones — and since there are a very limited number of data points of one limits the data to hurricanes, it makes sense to include tropical storm
of storm —
tropical cyclones — and since there are a very limited
number of data points of one limits the data to hurricanes, it makes sense to include tropical storm
of data points
of one limits the data to hurricanes, it makes sense to include tropical storm
of one limits the data to hurricanes, it makes sense to include
tropical storms.
Fig. 1:
Number of storms every 5 - year interval since 1850 divided in 6 different categories
of severities, with «
Tropical Storm» as the least and «Category 5» as the most powerful
cyclones.
Whether
tropical cyclones impact the US is not a function
of the
number of cyclones altogether.
Fig. 2 shows predictions with a simple model that predicts the
number of tropical cyclones (NTC and n) in the North Atlantic based on the area
of warm sea surface (A) and the NINO3.4 index.
However it is also likely — in other words there is a 66 percent to 100 percent probability — that overall there will be either a decrease or essentially no change in the
number of tropical cyclones.
We know that the
number of tropical cyclones is influenced by several factors: the seasonal cycle, the geography, ocean temperatures and the wind structure in the atmosphere.
According to the IPCC AR5, however, there are little indications
of a change in the
number of tropical cyclones, although they are becoming more intense (p. 107, TS.5.8.4 Cy
cyclones, although they are becoming more intense (p. 107, TS.5.8.4
CyclonesCyclones):
It also states that even though there is some evidence
of increased intensity, «There is no clear trend in the annual
numbers of tropical cyclones.»
This is because in the latter part
of the time series there is a decrease in the total
number of tropical cyclones, largely owing to a large multidecadal
cyclone in the WPAC (which comprises 40 %
of the global
tropical cyclones), see Fig 3 in Webster et al..
The total
number of typhoons might actually go up a bit because
of the promotion
of some
tropical storms to typhoons, but
of course the distinction between these classes
of cyclone is arbitrary.
So, we can only tell for sure with hindsight whether the high
number of tropical cyclones are an indication
of a climate change (let's hope it's not!).
There is no clear trend in the annual
numbers of tropical cyclones.
But there is a substantial body
of research that has been done looking at how various factors (such as El Nino, the North Atlantic Oscillation, etc.) may influence Atlantic
tropical cyclone numbers.
--
Tropical cyclones near average overall / Historic Super Typhoon: The number of tropical cyclones during 2013 was slightly above average, with a total of 94 storms, in comparison to the 1981 - 2010 averag
Tropical cyclones near average overall / Historic Super Typhoon: The
number of tropical cyclones during 2013 was slightly above average, with a total of 94 storms, in comparison to the 1981 - 2010 averag
tropical cyclones during 2013 was slightly above average, with a total
of 94 storms, in comparison to the 1981 - 2010 average
of 89.
I wonder if the fact the higher SSTs will lead to somewhat longer seasons (and 2005 certainly had that), and larger sea - surface area where TCs might form, would serve to counteract the effect you describe, and still lead, net - net, to an increase in the
number of tropical cyclones with higher SSTs.
The top time series is the
number of global
tropical cyclones that reached at least hurricane - force (maximum lifetime wind speed exceeds 64 - knots).
HOWEVER, the
number of tropical cyclones with intensity greater than 34 - knots has remained at the 30 - year average (83 storms per year).
See Wikipedia for the long term trend in
number of storms: «While the
number of storms in the Atlantic has increased since 1995, there seems to be no signs
of a global trend; the global
number of tropical cyclones remains about 90 ± 10.»
Did you ever realise that this is not the result
of global cooling or the lack
of global warming, but an increased
number of tropical cyclones likely as a result
of global warming?
I note that the recent paper shows a dramatic uptick in storm activity that has been convincingly refuted by «strong evidence that there has been no systematic change in the
number of north Atlantic
tropical cyclones during the 20th century.»
For example, the latest report from the IPCC says while there could be a decrease or no change in the
number of tropical cyclones occurring globally through the 21st century, they are likely to be stronger when they do strike.
These maps show the average
number of tropical cyclones through the Australian region and surrounding waters in El Niño years, La Niña years, neutral years and using all years
of data.
Worldwide there will likely be an average increase in the maximum wind speed
of tropical cyclones (hurricanes and typhoons)
of 2 to 11 %.6 Because
of the way extremes respond to changes such as these, Category 4 and 5 hurricanes are expected to nearly double in
number by the end
of the century.7 The rate
of rainfall associated with
tropical cyclones, an important factor in flooding, is expected to increase approximately 20 % within 100 km
of the center
of these storms.8
[20] In the US southern climatic region (which extends from Mississippi through Texas) the
number of daily heavy precipitation events has increased by 25 percent over the long - term average, and
tropical cyclones contributed 48 percent
of that increase.
Tropical cyclones are relatively rare, averaging around 90 a year, and that
number fluctuates annually and from decade to decade − largely because
of natural causes.
While there has been a recent increase in the
number of landfalling US hurricanes, the increase in
tropical cyclone - associated heavy events is much higher than would be expected from the pre-1994 association between the two, indicating that the upward trend in heavy precipitation events is due to an increase in the
number of heavy precipitation events per system.
«For the high emissions scenario, it is likely that the frequency
of hot days will increase by a factor
of 10 in most regions
of the world», said Thomas Stocker the other Co-chair
of Working Group I. «Likewise, heavy precipitation will occur more often, and the wind speed
of tropical cyclones will increase while their
number will likely remain constant or decrease».
Utilizing the current satellite picture
of a
tropical cyclone, one matches the image versus a
number of possible pattern types: Curved band Pattern, Shear Pattern, Eye Pattern, Central Dense Overcast (CDO) Pattern, Embedded Center Pattern or Central Cold Cover Pattern.
CI
numbers have been calibrated against aircraft measurements
of tropical cyclones in the Northwest Pacific and Atlantic basins.
The IPCC notes in its most recent scientific assessment that there are «[n] o robust trends in annual
numbers of tropical storms, hurricanes and major hurricanes counts have been identified over the past 100 years in the North Atlantic basin,» and that there are «no significant observed trends in global
tropical cyclone frequency.»
In the mid-2000s, a
number of researchers claimed that man - made global warming was causing a noticeable increase in the frequency and intensity
of tropical cyclones.
The Intergovernmental Panel on Climate Change reported in its most recent scientific assessment that «[n] o robust trends in annual
numbers of tropical storms, hurricanes, and major hurricanes... have been identified over the past 100 years in the North Atlantic basin,» and that there are «no significant observed trends in global
tropical cyclone frequency.»
In the summer (JJA) and autumn (SON)
of strong El Niño years,
tropical cyclone numbers increase markedly in the southeastern quadrant
of the western North Pacific (0 ° N — 17 ° N, 140 ° E — 180 ° E) and decrease in the northwestern quadrant (17 ° N — 30 ° N, 120 ° E — 140 ° E; Wang and Chan, 2002).
The 1990s and 2000s do seem to have had a larger
number of major
tropical cyclones than the 1970s and 1980s, but we can see from the longer records in Figure 11 (i.e., North Atlantic and West Pacific) that the 1970s were a fairly quiet era.
Although the devastation Typhoon Haiyan caused in the Philippines was horrendous, there does not appear to have been any long term trend in the
number of tropical cyclones reaching the Philippines, e.g., see Kubota & Chan, 2009 (Abstract; Google Scholar access).
Moreover, a record
number of 10
tropical cyclones or typhoons made landfall in Japan; the previous record was 6 (Levinson, 2005).