Atlantic Tropical Action 2014

[IntenseBlizzard2014]

It looks like it'll be quiet for a loooong time. 

[GaWx]

It looks like it'll be quiet for a loooong time.

Considering the lack of unfavorable upcoming MJO phases (coming across circle to phases 1/2 instead of going through 5-8 on top of circle), any relatively quiet period in the MDR would be consistent with oncoming El Niño climo/recent mainly -SOI fwiw.

[IntenseBlizzard2014]

Considering the lack of unfavorable upcoming MJO phases (coming across circle to phases 1/2 instead of going through 5-8 on top of circle), any relatively quiet period in the MDR would be consistent with oncoming El Niño climo/recent mainly -SOI fwiw.

 

Yeah, it sucks. Phases 1/2 favors more troughs along the EC and drier conditions in the Atlantic. It will be quite boring out in the Atlantic. 

[GaWx]

Yeah, it sucks. Phases 1/2 favors more troughs along the EC and drier conditions in the Atlantic. It will be quite boring out in the Atlantic.

Actually, phases 1, 2, and within the circle have been relatively favorable phases for Atlantic basin genesis during September. So, what I am saying is that often this predicted MJO setup of within circle followed by phases 1 and 2 would result in some geneses. If we see none over the next 10 days or so, I'd be suspecting the recent -SOI/Ninoish atmosphere. Note the lack of a sustained Bermuda high in the forecast. From my years of following the tropics, I've found a decent correlation between a rather persistent Bermuda high and Atlantic activity. I suspect there may be somewhat of a tendency for a weaker or less persistent Bermuda high when the SOI has been predominantly negative.

 

Edit: To add, I also strongly suspect a good correlation between a persistent -SOI and a drier than normal tropical Atlantic to follow. I've often mentioned that I believe that oncoming El Ninos don't tend to quiet things just because of increased MDR shear. So, I also think that an oncoming El Nino is often correlated with dryness in the MDR/above average SAL. So, the dryness is NOT a surprise to me.

[Ground Scouring]

Considering the lack of unfavorable upcoming MJO phases (coming across circle to phases 1/2 instead of going through 5-8 on top of circle), any relatively quiet period in the MDR would be consistent with oncoming El Niño climo/recent mainly -SOI fwiw.

What's weird is that the WPAC is also having one of its quietest seasons on record. A full month passed (02 August-07 September) without a TS in the WPAC. A full month without activity is highly unusual in the WPAC, even during cool ENSO events, and especially during an incipient +ENSO event as we see now. Only the EPAC has been above average. Perhaps the warmer water in the SW Pacific (leading to a lack of WWBs) and the suppressed convection/+OLR over Indonesia are responsible for the weaker activity in the WPAC this season.

 

I've found a decent correlation between a rather persistent Bermuda high and Atlantic activity. I suspect there may be somewhat of a tendency for a weaker or less persistent Bermuda high when the SOI has been predominantly negative.

Do you mean to say that a stronger Bermuda High = increased Atlantic activity? I thought that a weaker high = lower pressures = more activity, all other factors being equal.

[GaWx]

Do you mean to say that a stronger Bermuda High = increased Atlantic activity? I thought that a weaker high = lower pressures = more activity, all other factors being equal.

 

  What I believe happens is that a stronger Bermuda high makes it more conducive for low pressure to organize/strengthen and persist underneath it. Also, I think that there tends to be less westerly shear underneath a well stacked Bermuda high and more favorable conditions overall. Furthermore (not directly related to your question about increased activity), I think that a stronger Bermuda high tends to result in a lower frequency of  recurves well east of the US since the storms tend to go around the Bermuda high (one that is stacked well up into the atmosphere). Consider the modeling that has 91-L recurving near 55-65W. That wouldn't happen with a relatively stable/strong Bermuda high since the Bermuda high would be centered near that longitude. It would typically travel a good bit further west underneath the high.

[AvantHiatus]

Does not matter how dry the MDR is when you have such vigorous AEWs in the flow. 90L was a depression, arguably, for a brief time. If that can develop, this one surely can.

 

Additionally, the Euro and GFS strongly disagree w/500mb in the long-range. This is not a classic instant recurve scenario. The WAR on the european is very aggressive and is constantly delaying the East Coast cold front.

 

Take a look for yourself instead of swimming in pessimism and the "just because" mindset. Healthy 850mb circulation..

http://rammb.cira.colostate.edu/ramsdis/online/loop_meteosat.asp?data_folder=tropical/tropical_met_4km_visir2_floater&width=640&height=480&number_of_images_to_display=20

[Kory]

Does not matter how dry the MDR is when you have such vigorous AEWs in the flow. 90L was a depression, arguably, for a brief time. If that can develop, this one surely can.

 

Additionally, The Euro and GFS strongly disagree in the long-range. This is not a classic instant recurve scenario. The WAR on the european is very aggressive and is constantly delaying the East Coast cold front.

It certainly seems to be pulling some moisture from the ITCZ.  That was why 90L held on to it's convection in such hostile surrounding conditions.  The minute it detached it's inflow from the ITCZ, the storms seemed to collapse.  

[GaWx]

Additionally, the Euro and GFS strongly disagree w/500mb in the long-range. This is not a classic instant recurve scenario. The WAR on the european is very aggressive and is constantly delaying the East Coast cold front.

 

 

 I agree that it isn't at all a classic instant recurve if that means a recurve in the E Atlantic (say east of 50W). It isn't

that at all.

  Regarding a recurve in the western Atlantic: Of course, almost nothing in wx is set in stone. That's why I'm still going 95% as opposed to 100% chance of recurve east of the US. I do think that the NE US has a little bit higher chance (but still small) (Maritmes good bit higher) to get hit if the recurve is delayed enough than the SE US simply because there would appear to be no mechanism to get it over to the SE coast per the model consensus. There is way too much eastern US troughing along with no persistent Bermuda high. Now, IF this should happen to travel much further south than progged (into/through the Caribbean due to, perhaps, remaining very weak), then that would be a much different story. However, those odds are quite low imo.

[icebreaker5221]

Does not matter how dry the MDR is when you have such vigorous AEWs in the flow.

 

Actually, that's not really true at all.  Very vigorous AEWs can rapidly dissipate in an extremely dry environment, while a modest wave can grow into a MH in a sufficiently moist environment. 

[bluewave]

Actually, that's not really true at all.  Very vigorous AEWs can rapidly dissipate in an extremely dry environment, while a modest wave can grow into a MH in a sufficiently moist environment. 

 

Yeah, the increasing dry air  primary reason that the last major hurricane south of 20N in the Tropical Atlantic

was in 2010. Most systems since them have really struggled out there. I am not even sure if any storms can

make to cat 1 this season while still in that box like Humberto did last year.The best be may be a wave that

can survive to the subtropics like Cristobal and make it to hurricane strength.

[Weather.St]

Yeah, the increasing dry air  primary reason that the last major hurricane south of 20N in the Tropical Atlantic

was in 2010. Most systems since them have really struggled out there. I am not even sure if any storms can

make to cat 1 this season while still in that box like Humberto did last year.The best be may be a wave that

can survive to the subtropics like Cristobal and make it to hurricane strength.

Despite the drier air, we are still seeing  features that look relatively stronger than last year emerging off the west coast of Africa. In similar years with a persistent SAL in that region, we have seen storms move off the coast of Africa, and immediately dissipate. This year, things want to hold together and fight the SAL until the middle Atlantic, where humidities seem to dry out any additional fuel sources for thunderstorms. I am sort of wondering why they would be so hard pressed to fight the adverse conditions as opposed to last year when the conditions overtook the storms rather quickly.

[bluewave]

Despite the drier air, we are still seeing  features that look relatively stronger than last year emerging off the west coast of Africa. In similar years with a persistent SAL in that region, we have seen storms move off the coast of Africa, and immediately dissipate. This year, things want to hold together and fight the SAL until the middle Atlantic, where humidities seem to dry out any additional fuel sources for thunderstorms. I am sort of wondering why they would be so hard pressed to fight the adverse conditions as opposed to last year when the conditions overtook the storms rather quickly.

 

For the Tropical Atlantic east of 40W, we are still quieter than year last when we already had three named systems out 

there by this time. But the subtropical Atlantic north of the Caribbean is doing better.It says a lot about this

season when the most interesting development with Arthur was a disturbance which moved over the 

Southeastern U.S. and off the coast before blowing up. It was spared the trek through all the dry air to the

east so it did relatively well. If the current wave near the Cape Verdes develops,then  it will probably have to

hold together until recurving north of 20N before it can do better like Cristobal and Bertha did.

[AvantHiatus]

For the Tropical Atlantic east of 40W, we are still quieter than year last when we already had three named systems out 

there by this time. But the subtropical Atlantic north of the Caribbean is doing better.It says a lot about this

season when the most interesting development with Arthur was a disturbance which moved over the 

Southeastern U.S. and off the coast before blowing up. It was spared the trek through all the dry air to the

east so it did relatively well. If the current wave near the Cape Verdes develops,then  it will probably have to

hold together until recurving north of 20N before it can do better like Cristobal and Bertha did.

Look at the MJO phases. I think we were unlucky rather than the basin being worse off. 12z Euro is more bullish about 91L. I suspect we will have a couple more AEWs that develop in the month of September.

[icebreaker5221]

Well, looks like the Euro likes 91L now with the 12Z cycle.  Still looks like a fish tho. 

[Weather.St]

Look at the MJO phases. I think we were unlucky rather than the basin being worse off. 12z Euro is more bullish about 91L. I suspect we will have a couple more AEWs that develop in the month of September.

Kind of odd that the ECMWF is bullish, I usually expect the GFS to be more bullish about tropical cyclones..

[Kory]

Well, looks like the Euro likes 91L now with the 12Z cycle. Still looks like a fish tho.

Definitely a fish on that run with a trough like that off the East Coast. But it's sub 980 mbars on that run...Big change from 00z.

Where's Ground Scouring now that his beloved model is showing significant development of 91L?

[bluewave]

Look at the MJO phases. I think we were unlucky rather than the basin being worse off. 12z Euro is more bullish about 91L. I suspect we will have a couple more AEWs that develop in the month of September.

 

The Euro follows the Bertha and Cristobal script where 30N-40N is the new 20N. The dry air out over the Tropical

Atlantic really held back the potential with this MJO. Nearly the whole month of August was stuck in 1+2. If this

had occurred before the dry air of recent years, we would have probably had at least 10 named storms by now

instead of just 4. But it does look like the Euro wants to develop this wave more over the subtropical Atlantic

but it will be a fish.

[RGweathergeek]

From my very untrained mind but is the prevalence of Saharan dust possibly the new normal? Could an increase in tropical development by rising SST be offset by long-term drought in the Sahara in a climate change scenario? Could we see more of these long-duration dust events in the future? Just some thoughts and questions that have been rolling around in my mind. 

[bluewave]

From my very untrained mind but is the prevalence of Saharan dust possibly the new normal? Could an increase in tropical development by rising SST be offset by long-term drought in the Sahara in a climate change scenario? Could we see more of these long-duration dust events in the future? Just some thoughts and questions that have been rolling around in my mind. 

 

Impacts of Hadley circulation widening should be an interesting topic for research in the coming years.

 

http://www.oriadam.info/oriadam/HCW_Expansion_2014.pdf

[SouthernWx2]

Considering the lack of unfavorable upcoming MJO phases (coming across circle to phases 1/2 instead of going through 5-8 on top of circle), any relatively quiet period in the MDR would be consistent with oncoming El Niño climo/recent mainly -SOI fwiw.

 

Larry, methinks we're about to see some records broken

 

1) First time in a century with back-to-back seasons without a major Atlantic cane (not since 1913-1914).  

 

2) Also the longest period between US major landfalling hurricanes in at least 180 years (NHC/ HURDAT period of record 1851-present PLUS knowledge of major Florida hurricanes at Key West in October 1846 and Tampa Bay in September 1848).  This hasn't happened at least since the mid-1830's.

[NaoPos]

Larry, methinks we're about to see some records broken

 

1) First time in a century with back-to-back seasons without a major Atlantic cane (not since 1913-1914).  

 

2) Also the longest period between US major landfalling hurricanes in at least 180 years (NHC/ HURDAT period of record 1851-present PLUS knowledge of major Florida hurricanes at Key West in October 1846 and Tampa Bay in September 1848).  This hasn't happened at least since the mid-1830's.

EUro and GFS develop a fish storm next week that couldpossibly reach major status, so not sure that record is completely safe. Something to keep an eye on.

[Kory]

Impacts of Hadley circulation widening should be an interesting topic for research in the coming years.

 

http://www.oriadam.info/oriadam/HCW_Expansion_2014.pdf

The years mentioned in that paper coincide quite well with the PDO fluctuations.  Do you thing that may be a cause?

 

 

...the HC widening over the years 1979-1997 is primarily associated with global warming.  By contrast, the continued HC widening from 1997 to 2012 is mostly associated with Grad(SST) changes consistent with reduced tropics-to-midlatitude temperature contrasts, such as occur under La Niña.

 

[bluewave]

The years mentioned in that paper coincide quite well with the PDO fluctuations.  Do you thing that may be a cause?

 

 

 

 

Yes, their main conclusion is that the change since the late 90's are primarily ENSO and PDO related.

They provide charts near the bottom of the paper that show how the warmer midlatitude SST's have

weakened the temperature gradient between the tropics. The last few years have featured the very

warm North Pacific SST's and the Tropical Atlantic SST's have cooled.

[RGweathergeek]

Impacts of Hadley circulation widening should be an interesting topic for research in the coming years.

 

http://www.oriadam.info/oriadam/HCW_Expansion_2014.pdf

 Thank you for the link, even to my untrained eye I found this very interesting. This is why atmosphere science is so fascinating. You would think that warming SST because of climate change would correlate with increased tropical development, but HC widening may counteract any possible increase in tropical development. If this hypothesis holds true, decreased tropical development could be a mixed blessing, less damage and loss, but potentially decreased rainfall in the SE US and Gulf Coast. I know during times of drought Texas and the SE hope for tropical systems as drought-busters. Decreased tropical development could lead to longer droughts. All types of great food for thought. 

[Kory]

I'm paying close attention to the dying ULL near the Bahamas.  Models aren't too bullish on it, but this is one of the most favorable areas in the Atlantic basin.  Both the Euro and the GFS show a weak low level vorticity moving west into Florida and then into the Gulf (mainly as a surface trough).  Looks like shear will be a problem...hampering quick development.  

 

 

You can see the 850 mbar vorticity here:

 

Shear is relatively light, but it is expected to increase, which is possibly why the models don't develop it. 

[MarkSC]

I'm surprised NHC has not put invest status on the area in the Bahamas that Kory mentions. 

[Srain]

I'm surprised NHC has not put invest status on the area in the Bahamas that Kory mentions. 

Why would they? It is a TUTT that extends from the Bahamas to the SW into Cuba.

 

[AvantHiatus]

FWIW, the Nam develops this area. TUTTs can work down to the surface tho?

http://www.tropicaltidbits.com/analysis/models/nam/2014090906/nam_mslp_pcpn_eus.html

[MarkSC]

Favorable environment, dying TUTT, increasing convection, and some model support for weak development. If not Invest status, it at least warrants a mention in the TWO.