Atlantic Tropical Action 2011

[HurricaneJosh]

Unapologetic Tight Core Snob.

I know. I've got to stop being such a hurricane snot. Of course all types of hurricanes have their own unique coolness...

It's just that some are cooler than others.

[OSUmetstud]

the temperature of the Gulf and the Western Caribbean matters very little IMO this time of year. The Gulf and the western Caribbean were boiling in August, September, and October last year. The El Nino/-NAO was keeping the Gulf cold in the spring...and the eastern and central Atlantic the warmest on record. The persistent state of the -NAO during the summer kept the Western Atlantic ridge weak and allowed for significant recurvature. If we can manage to have a more +NAO state and a more stout western Atlantic ridge...that increases our chances for more landfalls.

[HurricaneJosh]

the temperature of the Gulf and the Western Caribbean matters very little IMO this time of year. The Gulf and the western Caribbean were boiling in August, September, and October last year. The El Nino/-NAO was keeping the Gulf cold in the spring...and the eastern and central Atlantic the warmest on record. The persistent state of the -NAO during the summer kept the Western Atlantic ridge weak and allowed for significant recurvature. If we can manage to have a more +NAO state and a more stout western Atlantic ridge...that increases our chances for more landfalls.

Yeah, good point. It really doesn't matter right now. Perhaps I'm just wanting to jump on what I perceive to be positive signals.

But, as you point out, it's really more about steering currents. Last year was a disappointment for American tropical dudes not because of oceanic heat content, but because of steering currents.

[wxmx]

Other than the TNA region and the area near Europe, there is little correlation between SSTAs and overall activity this time of the year. Usually the ocean currents transport the warmer SSTs thru the the Caribbean anyways, so it's better to have a warm TNA this time of the year (which it is, though not at record levels like last year). If the TNA stayed very warm during the peak of the season, then yes, early development would be more likely, hence the recurve chances would go up.

The role of the NAO wrt steering currents is not as straightforward as -NAO=high chance of recurve. As a matter of fact, it usually helps steer a cyclone farther west than during a +NAO period, especially in the E and C Atlantic, because the Azores ridge is weaker but positioned further south, so narrow ridging is quite common in the tropical Atlantic during -NAO periods, with little trough interaction... it is when the cyclone nears the North America landmass that things get messy (land isn't as trustful as ocean wrt mid/upper atmosphere configurations, as they get more chaotic...and this is more pronounced during summer because of the shorter wavelenghts). Also, a -NAO usually helps the tropical Atlantic SSTAs to rise because of the weaker Azores high near the surface.

[OSUmetstud]

Other than the TNA region and the area near Europe, there is little correlation between SSTAs and overall activity this time of the year. Usually the ocean currents transport the warmer SSTs thru the the Caribbean anyways, so it's better to have a warm TNA this time of the year (which it is, though not at record levels like last year). If the TNA stayed very warm during the peak of the season, then yes, early development would be more likely, hence the recurve chances would go up.

The role of the NAO wrt steering currents is not as straightforward as -NAO=high chance of recurve. As a matter of fact, it usually helps steer a cyclone farther west than during a +NAO period, especially in the E and C Atlantic, because the Azores ridge is weaker but positioned further south, so narrow ridging is quite common in the tropical Atlantic during -NAO periods, with little trough interaction... it is when the cyclone nears the North America landmass that things get messy (land isn't as trustful as ocean wrt mid/upper atmosphere configurations, as they get more chaotic...and this is more pronounced during summer because of the shorter wavelenghts). Also, a -NAO usually helps the tropical Atlantic SSTAs to rise because of the weaker Azores high near the surface.

I think Wes posted something at the conference last year about hurricanes tending to have more east-west tracks with a +NAO state and more south-north tracks with a -NAO state. I agree that a -NAO in the Spring and early Summer definitely helps to heat the SSTs up more due to the weaker high. There basically was no high whatsoever in the winter and spring last year lol.

[Floydbuster]

I know. I've got to stop being such a hurricane snot. Of course all types of hurricanes have their own unique coolness...

It's just that some are cooler than others.

I think I know what Josh means. From a hurricane chasing or hurricane tracking standpoint, the stronger the storm, the more anticipation.

Category 1, 2 and 3 hurricanes are bad, no doubt about it. Hurricane Jeanne was nasty in Florida, a solid 120 mph Cat-3 at landfall. Mobile homes were heavily damaged or destroyed, boats tossed, very extensive damage.

Category 4 and Category 5 hurricanes are something way different. I wouldn't even use the term "extreme" damage, I'd rather say, "violent" damage. The type of damage you see from F4 and F5 tornadoes that level towns in the Midwest is similar to what you see with hurricanes with landfalling sustained winds of 140+ mph.

That's an aerial view of Mahahual, Mexico where Hurricane Dean's sustained winds were 175 mph with higher gusts. Not much left...and the trees are even stripped bare.

[wxmx]

I think Wes posted something at the conference last year about hurricanes tending to have more east-west tracks with a +NAO state and more south-north tracks with a -NAO state. I agree that a -NAO in the Spring and early Summer definitely helps to heat the SSTs up more due to the weaker high. There basically was no high whatsoever in the winter and spring last year lol.

It's definitely the other way around, especially for low latitude cyclones in the deep tropics. The more zonal flow associated with a -NAO tend to steer the cyclones in a more east/west fashion. But if you are talking about hits in the East coast, specially from the Carolinas to the north, then yes, probably a +NAO is better... for GOM and Caribbean action a -NAO would be better. Probably the best setup for the East coast is some strong -NAO while we have a cyclone traversing the Atlantic, slowly going positive while closing to the coast, maybe. Let me try to find the papers to backup these claims, as I have read some things, not just pulling things from my behind

[wxmx]

No absolutes, but this Elsner's paper is worth reading

The regression indicates that straight-moving hurricanes are more common when the SOI is positive and the NAOI is negative.

[wxmx]

From here

[HM]

It's definitely the other way around, especially for low latitude cyclones in the deep tropics. The more zonal flow associated with a -NAO tend to steer the cyclones in a more east/west fashion. But if you are talking about hits in the East coast, specially from the Carolinas to the north, then yes, probably a +NAO is better... for GOM and Caribbean action a -NAO would be better. Probably the best setup for the East coast is some strong -NAO while we have a cyclone traversing the Atlantic, slowly going positive while closing to the coast, maybe. Let me try to find the papers to backup these claims, as I have read some things, not just pulling things from my behind

I agree. You want that classic Southeast Canadian high sitting there for an East Coast hit, as your image indicates. I haven't done the research and don't know of any studies but I wonder if the NAO phase shift works for East Coast hurricanes like it does with enhanced precipitation events and nor'easters. The -NAO could help aid in deep Atlantic development and a westward steering toward the mainland; and then as the +NAO comes on, the ridge forms over Canada, allowing for it to turn toward the coast.

[OSUmetstud]

I agree. You want that classic Southeast Canadian high sitting there for an East Coast hit, as your image indicates. I haven't done the research and don't know of any studies but I wonder if the NAO phase shift works for East Coast hurricanes like it does with enhanced precipitation events and nor'easters. The -NAO could help aid in deep Atlantic development and a westward steering toward the mainland; and then as the +NAO comes on, the ridge forms over Canada, allowing for it to turn toward the coast.

hmmm...that makes sense. I wish Wes were here to kinda backup what was said. I'm really pretty sure he said +NAO was better for longitudinal moving storms...

[turtlehurricane]

This is Florida's year.. I feel it in my bones

LOL. Nah, man your bones can't feel hurricanes that haven't even happened yet, fact.

[rainstorm]

lets keep an eye on things.

[k***]

But of future concern is the still-active ITCZ, which is showing discrete development of impulses already near Ecuador, over western Brazil, and approaching Guyana. The pattern for clearly-defined convective clusters with defined circulation favors and early and intense start to the 2011 Atlantic Basin tropical cyclone season.

from LC

I don't care how many convective clusters there are, virtually nothing will be coming out of there in june or early july.

[flwxwatcher45]

lets keep an eye on things.

Your buddy LC still looking for an early start to the season, according to his latest newsletter..

The storm sequence across the western Atlantic Ocean and the lower 48 states may draw most of the attention here (note the MCS with severe weather in lower Appalachia and the Piedmont). But of future concern is the still-active ITCZ, which is showing discrete development of impulses already near Ecuador, over western Brazil, and approaching Guyana. The pattern for clearly-defined convective clusters with defined circulation favors and early and intense start to the 2011 Atlantic Basin tropical cyclone season.

[rainstorm]

i saw that

[gil888]

[quote name='rainstorm', on 09 April 2011 - 09:04 PM, said:

But of future concern is the still-active ITCZ, which is showing discrete development of impulses already near Ecuador, over western Brazil, and approaching Guyana. The pattern for clearly-defined convective clusters with defined circulation favors and early and intense start to the 2011 Atlantic Basin tropical cyclone season.

I believe the active ITCZ is well-related to a substantial MJO wave coming through the Atlantic basin. If a similarly defined wave comes through at the end of May/early June-- I would think that would favor something in the western Caribbean/GOM. Seasonally, I'm not sure it means much, because conditions have generally been more favorable than average in terms of lower shear, warmer Atlc waters, and no signs of El Nino. Well-defined MJO pulses could focus the season, however, more than we have seen in recent years... ?

[k***]

I guess the bright side is that we have well-defined MJO pulses? Last year they were a little bit sketchy...

[OKpowdah]

We better hope for an early start, because it's going to be a very lame end IMO

[HurricaneJosh]

We better hope for an early start, because it's going to be a very lame end IMO

How come? Are you envisioning a late-season El Nino?

[OKpowdah]

How come? Are you envisioning a late-season El Nino?

A few factors that I'm looking at. A somewhat El Nino atmosphere may play a role. Also the easterly shear zone of the QBO is descending pretty quickly now. The easterly shear zone corresponds to a warmer stratosphere which leads to a lower tropopause ~10-15 degrees off the equator

[rainstorm]

http://www.weatherbell.com/jb/

jb explains trough splitting and cane season.

[Ed Lizard]

http://www.weatherbell.com/jb/

jb explains trough splitting and cane season.

I see more global warming, myself, and nothing tropical, at that link.

JB, trough splitting, ventilated waves, good stuff. But I didn't see it today.

[rainstorm]

you have to click on previous vids

[turtlehurricane]

A few factors that I'm looking at. A somewhat El Nino atmosphere may play a role. Also the easterly shear zone of the QBO is descending pretty quickly now. The easterly shear zone corresponds to a warmer stratosphere which leads to a lower tropopause ~10-15 degrees off the equator

Is this a sign of a QBO phase shift or is it just a normal oscillation with a shorter frequency than the QBO?

[OKpowdah]

Is this a sign of a QBO phase shift or is it just a normal oscillation with a shorter frequency than the QBO?

It's a sign of the QBO phase shift. The westerly anomalies are steadily weakening and the easterlies have started to descend over the last month. At this rate the overall characteristic of the stratosphere will be dictated by easterly vertical shear by the autumn.

[flwxwatcher45]

2010 NHC forecast verification report.

http://www.nhc.noaa.gov/verification/pdfs/Verification_2010.pdf

[phil882]

A few factors that I'm looking at. A somewhat El Nino atmosphere may play a role. Also the easterly shear zone of the QBO is descending pretty quickly now. The easterly shear zone corresponds to a warmer stratosphere which leads to a lower tropopause ~10-15 degrees off the equator

Hmm that sounds like it would have a general negative impact on TC's due to the lower tropopause, meaning deep convection won't attain as high of an altitude than under a westerly QBO configuration. In addition, an east based QBO will provide additional easterly shear above the troposphere, so what overshooting tops do occur will likely not be as vertically stacked.

[am19psu]

In addition, an east based QBO will provide additional easterly shear above the troposphere, so what overshooting tops do occur will likely not be as vertically stacked.

All of the research I've seen shows basically no significant effect from wind stress at the tropopause, either by easterly winds decreasing shear or westerly winds increasing shear.

[Ed Lizard]

All of the research I've seen shows basically no significant effect from wind stress at the tropopause, either by easterly winds decreasing shear or westerly winds increasing shear.

Back in the 90s, I don't recall the specific year, Dr. Gray's regressions had led him to using QBO phase as a predictor of TC activity.

Back when sub-Saharan rainfall was also a predictor.

Off to the Googlesphere..

1995...

http://climate.engr....faq_695_23.html

* Stratospheric quasi-biennial oscillation (QBO) - During the 12 to 15 months when the equatorial stratosphere has the winds blowing from the east (east phase QBO), Atlantic basin tropical cyclone activity is reduced. The east phase is followed by 13 to 16 months of westerly winds in the equatorial stratosphere where the Atlantic activity is increased. It is believed (but not demonstrated) that the reduced activity in east years is due to increased lower stratospheric to upper tropospheric vertical shear which may disrupt the tropical cyclone structure.