Northern Hemisphere achieves record quiet start

[HURAKAN]

(Edit from Portastorm) Jeff Masters Blog posting

Why so quiet in the Atlantic?

The Tropical Atlantic is quiet, and there are no threat areas to discuss today. The Invest 93 system we were tracking has been destroyed by dry air and wind shear. There are a couple of long-range threats suggested by some of the models--the GFS model predicts a tropical depression could form off the coast of Mississippi six days from now, and the NOGAPS model thinks something could get going in the Gulf of Mexico's Bay of Campeche seven days from now. Neither of these possibilities are worthy of concern at present. Overall, it's been a surprisingly quiet August, considering the pre-season predictions of a hyperactive season. According the National Hurricane Center, this hurricane season has been exactly average so far. There have been three named storms and one hurricane as of August 12. The average date of formation of the third named storm is August 13. One hurricane typically forms by August 10. One reason for this year's inactivity may be an unusual number of upper-level low pressure systems that have paraded across the tropical Atlantic. These lows, also called Tropical Upper Tropospheric Trough (TUTT) lows, tend to bring high wind shear that inhibits tropical cyclone formation. The other major factor appears to be that vertical instability has been unusually low in the Atlantic over the past month. Instability is measured as the difference in temperature between the surface and the top of the troposphere (the highest altitude that thunderstorm tops can penetrate to.) If the surface is very warm and the top of the troposphere is cold, an unstable atmosphere results, which helps to enhance thunderstorm updrafts and promote hurricane development. Since SSTs in the Atlantic are at record highs, enhancing instability, something else must be going on. Dry air can act to reduce instability, and it appears that an unusually dry atmosphere over the Atlantic this month is responsible for the lack of instability.

A record quiet start to the 2010 tropical cyclone season in the Northern Hemisphere

What is really odd about this year, though, is the lack of tropical cyclone activity across the entire Northern Hemisphere. Usually, if one ocean basin is experiencing a quiet season, one of the other ocean basins is going bonkers. That is not the case this year. Over in the Eastern Pacific, there have been five named storms and two hurricanes. The average is seven named storms and four hurricanes for this point in the season. This year's quiet season is not too surprising, since there is a moderate La Niña event underway, and La Niña conditions usually supresses Eastern Pacific hurricane activity. But over in the Western Pacific, which usually generates more tropical cyclones than any ocean basin on Earth, it has been a near-record quiet season. Just four named storms have occurred in the West Pacific this year, and the average for this date is eleven. Only one typhoon season has had fewer named storms this late in the season--1998, with just three. The total number of named storms in the Northern Hemisphere thus far this year is fifteen, which is the fewest since reliable records began in 1948. Second place belongs to 1983 and 1957, with eighteen named storms. According to an email I received from NOAA hurricane researcher Gabe Vecchi, the lack of tropical cyclones so far this year in the Northern Hemisphere is between a 1-in-80 and 1-in-100 year event.

So, what is causing this quiet tropical cyclone season? One possibility is that since Northern Hemisphere land areas have heated up to record temperatures this summer, this has created strong rising motion over the continents. This rising motion must be compensated by strong sinking motion over the adjacent oceans in order to conserve mass. Sinking air causes drying and an increase in stability. Another possibility is that the unusual jet stream configuration that is responsible for the Russia heat wave and record flooding in Pakistan is also bringing dry, stable air to the Northern Hemisphere's tropical cyclone breeding grounds. It is also possible that climate change is causing the reduction in tropical cyclone activity, for a variety of complex reasons. Computer simulations of a future warmer climate generally show a reduction in global number of tropical cyclones (though the strongest storms get stronger), and it is possible we are seeing a preview of that future climate. Or, this year's quietness may simply be natural variability. It will be interesting to see when the Russian heat wave breaks if vertical instability over the Atlantic increases back to normal levels. Current forecasts from the GFS and ECMWF models project the Russian heat wave to break late next week.

Link - http://www.wunderground.com/blog/JeffMa ... rynum=1575

[ConvergenceZone]

It is also possible that climate change is causing the reduction in tropical cyclone activity, for a variety of complex reasons.

This part from Jeff Masters is particular interesting. It makes me wonder if that means the rest of the season might be fairly quiet as well??...

I guess us "naysayers" were on to something afterall

[Nimbus]

Hurricanes are just heat engines in the final analysis. Going into fall we have the warm ocean heat content at the surface with usually lower tropospheric temperatures above. That is an interesting angle about the higher than normal continental land temperatures causing dry air to subside over the tropical ocean areas this summer. If that was the primary detrimental factor for development this fall could be interesting. A sudden reversal in the pattern might leave us with a cold troposphere over higher than normal SST's. Abajan and some other storm2k posters have been speculating about such an event in another thread.

[KWT]

I keep saying this but lets look at when this started...2007....

When did the Solar min really kick in...yep guess what...2007 as well. I don't think its pure fluke this has happened at the same time as a prolonged min.

[JonathanBelles]

I must mention however that the Atlantic is above average so far for activity in terms of ACE and hurricanes.

[Hurricanehink]

Now, I read that article earlier, but I notice it doesn't mention anything about the North Indian Ocean. Is that intentional do you think? Or, maybe since activity is so minimal in an average year, that it doesn't matter? If you think about it, the NIO has actually been above average. It's had three named storms, two of which JTWC had as 65+ storms (and one, Phet, being one of the strongest storms in the Arabian Sea).