by Steve Goddard
The Atlantic Hurricane Basin remains dead quiet, and is now falling below the 1944-2005 average.
http://www.weatherstreet.com/hurricane/2010/Hurricane-Atlantic-2010.htm
I have not spent a lot of time studying hurricanes, but I have read that the “purpose” of hurricanes is to move heat quickly from the tropics to higher latitudes. Heat flow is always driven by differences in temperature. If two places were at the same temperature, there would be no heat flow.
Suppose that temperatures at higher latitudes (60N) were very warm – as they have been. What motivation would there be for hurricanes to form? The video and stil below shows UNISYS SST anomalies, with all anomalies between -1.0°C and +1.0°C removed.
Note that the Atlantic hurricane basin has very few places which are warmer than 1.0°C above normal. This agrees with Bob Tisdale’s graph.
By contrast, SST anomalies in the North Atlantic are far above normal. The difference in temperature between the tropical and north Atlantic is far below normal. Supposedly, it is that difference which gives hurricanes their raison d’être .
Things can change quickly. 1950 was the second most active hurricane season on record, and the first hurricane didn’t form until August 12.
Does it make sense that the heat engine which drives hurricane formation is basically shut down? What do you think?
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“By contrast, SST anomalies in the North Atlantic are far above normal. The difference in temperature between the tropical and north Atlantic is far below normal. Supposedly, it is that difference which gives hurricanes their raison d’être .”
In the spirit of skepticism, I find this reasoning questionable.
Yes, the thermal gradient between tropical and polar regions is a driving force behind globally observed wind and weather patterns. But it doesn’t necessarily hold true that a specific warm area in the North Atlantic would have a direct impact on the rate of cyclone formation in the Tropical Atlantic. I can’t see any obvious mechanism of causality. Could someone explain it?
Ian W makes an excellent point about temperature vs. enthalpy. Are <a href="http://en.wikipedia.org/wiki/Skew_T"Skew-T charts available over the ocean? It seems those might be useful.
Ian W says:
August 15, 2010 at 5:34 am
I have not seen a ‘heat’ mapping or a ‘heat graph’ in any of the articles on global warming, yet it is heat energy that should be being measured.
Hi Ian.
On the http://hurricanetrack.com premium site, there are TCHP (Tropical cyclone heat potential) maps that are used as a background for the tracks of each named storm. Shows the full heat content of the Atlantic basin and the Caribbean and GoM are ready to “go”.
The scale of that motion is much larger than the scale of a forming hurricane. Suppose a large temperature difference led to stronger winds in the Hadley Cell (and also the Ferrel Cell north of the tropics). I’d expect that to create more vertical wind shear (a velocity change in the wind wrt to altitude) and that would squash TS development.
While tropical storms do move a huge amount of heat north, I think it’s more side effect than driver.
Extratropical “baroclinic” storms, on the other hand, do depend on horizontal temeperature differences over distances and include cold and warm fronts that exchange heat basically north and south. Those I’d expect to increase in intensity with greater temperature differences, and that’s at odds with claims that the Arctic will warm more than mid-latitudes. Whole different subject.
I’m pretty much mystified as to what’s going on in the Atlantic now. I’m going to avoid speculation, there will be plenty of analysis from people with better insight than me.
BTW, most people have likely missed it, but I’ve been in a bit of a discussion about TS genesis over at http://wattsupwiththat.com/2010/08/10/klotzbach-on-atlantic-hurricane-season-analysis/#comment-456892 – I see the discussion is continuing, I haven’t read the new posts there yet.
That link includes some pointers to “Divene Winds” by Kerry Emanuel, another good book on hurricanes, though Emanuel is more theorist (and AGW supporter) than observer, and when it comes to tropical storms, nature toys even more with theorists than observers.
“The U.S. landfall of major hurricanes Dennis, Katrina, Rita and Wilma in 2005 and the four Southeast landfalling hurricanes of 2004 – Charley, Frances, Ivan and Jeanne, raised questions about the possible role that global warming played in those two unusually destructive seasons. In addition, three category 2 hurricanes (Dolly, Gustav and Ike) pummeled the Gulf Coast in 2008 causing considerable devastation. Some researchers have tried to link the rising CO2 levels with SST [Sea Surface Temperatures] increases during the late 20th century and say that this has brought on higher levels of hurricane intensity.”
“These speculations that hurricane intensity has increased have been given much media attention; however, we believe that they are not valid, given current observational data.”
This is from “Extended Range Forecast of Atlantic Seasonal Hurricane Activity and U.S. Landfall Strike Probability for 2010” (Dr. William Gray, Dr. Phil Klotzbach, Colorado State University, part 10, June 2 ’10, .pdf), http://hurricane.atmos.colostate.edu/Forecasts/2010/june2010/jun2010.pdf
Several years ago, I read an article (I think on Brett Anderson’s Accuweather blog) speculating that polar amplification would lead to reduced hurricanes. This is where I got the idea from.
It could be that filtering out average SST’s is a proxy for weather system pressure gradient differences between fronts. Wonder what those would show looking back at active years. The Jet stream is nearly non-existent and very messed up right now with no organized flow or connected loops, so large frontal systems are not being pushed in succession or jammed up to each other. Could that be the reason? No significant battles between systems because the Jet Stream, in its confused state of mind, is taking a nap?
http://squall.sfsu.edu/gif/jetstream_norhem_00.gif
Joe Bastardi posted at Accuwx earlier this week (pro site) on this same topic. His take was it has to do more with the warmth over North Am then the warm over the North Atlantic. Pre-season, he was forecasting above average tropical activity for the Atlantic basin. He is expecting activity to increase significantly as North Am cools. He is also expecting it to continue later into the year than usual
stevengoddard says: {August 15, 2010 at 6:26 am}
“Tom in Florida
The point is that the difference in temperature is lower than normal.”
Yes, I understand you say that but perhaps you should show the actual temperatures and see what the real difference is. The below link shows both actual mean temps and the anomalies for the Atlantic.
http://www.cpc.ncep.noaa.gov/products/hurricane/atlsst.html
richard telford ,
I read these posts to get information and better understand what may actually be what.
Apparently you have a take on this subject that is more learned than Goddard’s, would you put forward your argument so I can learn?
The two charts suggest that, so far, 2010 is average with regard to storms. The problem is that the average is 1. Had there been two we would now be 100% above average, and if three, we would be right up there with the busy 2005 season. Thus, until about mid-September – what is there to talk about?
The really odd thing about these charts (other than not knowing who prepared them) is that the 2010 forecast shown in red on the right side does not include the 1944-2005 average. What has happened to the concept of “regressing toward the mean”? – not part of climate science, I guess!
The exchange-of-heat idea expressed in this posting is – in principle – a correct one. However, it is too simple. Think of the atmosphere as music. One needs all the notes to have a proper experience. If you take all of some one note out of the music it will not sound correctly. All the rest of the music is still there – it just doesn’t work.
The point is that there is still warmth in the tropical ocean (a large area) and not so much in the northern latitudes (a smaller area). At the moment a part is missing. When and if that part enters the system, then the hurricane season will ramp up. We do not, at the moment, know what the missing part is. That’s what the planned GRIP study might find out:
http://wattsupwiththat.com/2010/08/11/nasa-to-get-a-grip-on-hurricane-formation/#more-23281
And as the charts shown suggest — they have chosen to get the effort underway in time for an expected ramp-up. That is, they are playing the average. Someone, maybe the funding agency, understands this concept.
Alert Michael Mann! Apparently, global warming has killed off the butterflies.
The “heat engine” is always working. In fact, it works better in the moist subtropical zones when upper-air wind shear is blowing, and the heat from Tstorms & showers is diffused quickly into the upper atmosphere. Only when the shear decreases to the point where it cannot diffuse & move away the heat effectively, does the next aspect come into effect — tropical storms.
There is little historical support for the high number of hurricanes [8-14] being predicted for the La Nina year 2010. The previous pattern of the high number of hurricanes during more recent La Nina years 1995-2007 seems to have ended.
The average since 1904 for La Nina years is about 6.3 hurricanes [highest 11, lowest 3]
60 % of the LA Nina years have had 6 hurricanes or less.
During the previous global cool period [say 1964-1975] there was an average of only about 5 hurricanes during La Nina years
My best estimate is about 4-5 hurricanes [ max of 6] this year as we are again at the start of a 10-30 year cooling period.[so we all claim?]
Tom in Florida, your link shows me that temps are cooling since July. So to me, where the temps were once pretty good for a riproaring season, it seems less so now.
“Dave Springer says:
August 15, 2010 at 5:16 am
richard telford says:
August 15, 2010 at 2:17 am
another post with Goddard revelling in his ignorance.
Welcome to the science of climatology.
When in Rome do as the Romans do.”
Or perhaps, when in Romm, do as the Rommans do!
Tropical fish here…. Although heat is an important component and heat distribution could well have a strong impact, based on my long observational experience while living all my life in the tropics, there has not been a single predictive factor that can be identified as “the smoking gun” of hurricane formation and hence the difficulty in long-range prediction using a single factor.
Personally, my belief (yes only a belief) is that transient synoptic and mesoscale patterns have the most influence. And sure, one could make that case that these could in the end be related to temperature, although I suspect it is the other way around.
I might be all wrong about this but I believe hurricane formation needs an East-West corridor in the ocean with widely spaced pressure gradients North and South, while at the same time this corridor must be bordered at the point of formation by two relatively distant counterrotating upper level systems, one North, one South, and with winds just strong and balanced enough and no more, to have the right effect on the corridor so that the environment for large thunderstorms becomes conducive for spin development.
This can even happen over land, as I’ve seen giant thunderstorms come off the coast of Africa already spinning, and those usually turn into hurricanes pretty quickly once over water.
So far this year it has not happened, not that it couldn’t happen at any time, and hence the long term unpredictability of these phenomena. I watch for those conditions to develop daily on the global vapor satellite movie here:
http://www.nrlmry.navy.mil/sat-bin/display10.cgi?SIZE=full&PHOT=yes&AREA=global/stitched&PROD=vapor&TYPE=ssmi&NAV=global&DISPLAY=Latest&ARCHIVE=Latest&CGI=global.cgi&CURRENT=20100815.1200.multisat.wv.stitched.Global.x.jpg&MOSAIC_SCALE=15
Just a pet theory of course :). But, if by NOAA’s admission, synoptic and mesoscale pattern prediction beyond 10-days is a coin toss, and should these turn out to be important in hurricane formation, how could we then predict hurricane formation more that 10-days in advance?
I think we get a record breaking cold winter this year.
In our part of Florida, it has not been a typical summer. It’s been much drier than normal (we’re short about 18 inches of rain) with very few of the typical summer thunderstorms, although a few have started lately. We’d normally be pumping the canals every few weeks, and this year they are dry. One would think that’s unrelated to what is going on off the west coast of Africa where our hurricanes originate, but maybe not?
Yes, the annual hurricane forecast is a regular joke here in Florida. Hurricane track prediction is another area rife with comedy. About the only year they got the tracks right was 2005 (2006?), if memory serves, and that year it seems like they nailed every one.
This has all the hallmarks of something that is not well understood. We’d all have a bit more respect for these folks if they’d simply admit it.
Gerry
Ian W: You wrote, “Perhaps the air in the mid-latitudes is just slightly drier than normal as the jet stream has moved more equatorwards in the last few years…”
I have been searching for a dataset that illustrates this. Do you know of one?
Would some of those ‘failed’ hurricanes this year, have even been classified as hurricanes in the 1950s, before the advent of satellite monitoring?
.
>>thermal gradient is like water pressure,
>>if you don’t turn on the tap, there is no flow,
In a nutshell….
Hurricanes are simply low pressure systems that get tightly wound up because of a lack of Coriolis force in the tropical regions (because the Earth is ‘fatter’ there).
Low pressure systems form when jetstreams move vast quantities of upper air out of a region.
Jetstreams form when columns of warm and cold air come into close proximity
However, the jetstreams have been all over the place this year (from a European perspective). They were more southerly than usual this winter (hence the cold winter), and they were still southerly this summer (hence Russia bakes).
I have never studied the jetstreams in regard to Atlantic hurricane formation, but I can bet that the latitude of the upper jetstreams is important.
.
The current NHC discussion notes mention “A large area of dry air and Saharan dust is E of the wave axis to west Africa.”
Saharan dust is important – it blocks sunlight at mid-level altitudes and that both heats the air (reducing convective potential) and reduces sea surface heating (reducing energy input to surface air and reducing convective potential).
Mid level dry air is important because it evaporates rain (reducing convection potential).
Things to watch, along with the cooler SSTs feeding in from the north.
Ocean’s Color Affects Hurricane Paths
http://www.sciencedaily.com/releases/2010/08/100813121916.htm
“In the study, to be published in an upcoming issue of Geophysical Research Letters, a journal of the American Geophysical Union, Gnanadesikan’s team describes how a drop in chlorophyll concentration, and the corresponding reduction in ocean color, could cause a decrease in the formation of hurricanes in the color-depleted zone. Although the study looks at the effects of a simulated drop in the phytoplankton population (and therefore in the ocean’s green tint), recently-published research argued that global phytoplankton populations have been steadily declining over the last century.”
Scratching my head.
http://www.aoml.noaa.gov/phod/cyclone/data/
This is the site for the TCHP maps.