Atlantic Tropical Action 2013

[Ground Scouring]

 I'm sorry I missed this. I will try to give a more substantial answer in the future but clearly the 2010-2012 period has been notably drier in the mid-upper levels of the Tropical Atlantic than 2002-05. Instability is calculated here using theta-e. A combination of the Mid Latitude pattern for ASO (PDO-AMO-Drought-Polar related, producing a stronger anticyclone over 60W in Atlantic) and the explosion from the IO (an increase in tropical forcing here) strengthening the African-Indo Hadley Cell are the direct reasons. The Mid Latitude pattern is responsible for an increased flux of stability from the north and it is working in tandem with the strengthened Hadley Cell too (the combination has produced a large-scale deformation in the mid-upper levels over the Tropical Atlantic and widespread warmer than normal upper levels across the Atlantic). The enhancement here may seem counterintuitive but it has significantly increased the upper level easterly jet into South America, cirrus/outflow production into Atlantic (a warming agent) and general mass flux westward. So while the African waves may get beefier and the ITCZ may come substantially further north in our current regime, it becomes very sensitive to Mid Latitude influences and upper level exhaust. Someone needs to cool down the African-Indian Hadley Cell!  

 

While I agree that it is too early to relate this to climate change, it could work out this way that the Atlantic sees the strongest reduction in instability. See my post above.

As usual, a great explanation. I am examining the latest trends in the IOSD and the early-summer monsoonal convection over the Punjabi regions to determine whether an enhanced anticyclone will be present near the southern Indian subcontinent this boreal summer. Based upon OI SSTA, the +IOSD regime in April 2010-2012, with a lag through MJJ period, seems to have been a factor in the increased subsidence / reduced vertical instability in the Eastern Atlantic since 2010, mainly but not solely due to the influx of a very stable Saharan air mass / heat ridge. In the following image, the +IOSD is very evident due to the strong warm anomaly over the SW Indian Ocean, which means a somewhat cooler IO / stronger temperature gradient north of the equator, which leads to an enhanced summer monsoon over the Punjab.

 

 

Unsurprisingly, the SSTA gradient supported strong +OLR over the Arabian Sea just N of the equator:

 

 

Note the enhanced low-level trades / 700-mb anticyclone over the N Indian Ocean, along with the enhanced monsoonal westerlies near 5-10N 60E, in this composite from the same period:

 

 

This year, however, the IOSD in the austral winter appears to have gone sharply negative. The April 2013 OI SSTA shows a sharp reversal over the SW Indian Ocean, with cooler anomalies predominating over the N IO basin, thereby resulting in a suppressed or delayed Punjabi monsoon this summer.

 

 

The 700-mb anomalies in April 2013 show prevailing westerlies dominating the N IO basin, a sharp reversal from April 2010-2012:

 

 

I would say that all these factors point to a more-unstable Atlantic basin than what we have been seeing, relatively, since 2010. I do know that the GLAAM has been unfavorable for the Atlantic recently and, despite a recent dip in April, has been sharply on the increase this month. Nevertheless, is not such a strongly positive variation often a precursor to an unstable GLAAM regimen rather than a sustained + regimen? Am I on the right track?

[wxtrackercody]

The 18z GFS was by far the most bullish with this potential Caribbean storm at the end of May.

 

Starts to develop in earnest by 276 hours; makes landfall in Cuba as a tropical storm and then intensifies into what appears to be a minimal hurricane as it moved through the Bahamas and begins to curve northward.

 

[thewxmann]

FWIW, vertical instability across the Trop Atl has been below avg thus far in 2013:

 

[Ed Lizard]

The 18z GFS was by far the most bullish with this potential Caribbean storm at the end of May.

 

Starts to develop in earnest by 276 hours; makes landfall in Cuba as a tropical storm and then intensifies into what appears to be a minimal hurricane as it moved through the Bahamas and begins to curve northward

Per video previous page, GFS MJO may be a little fast, GEFS MJO members look to be getting to the right area, but look dampened.   Euro slower.  I'll keep my hopes up for June.  Just my impression of thread dynamics, its early now, people are pretty relaxed, but once well into the season, people won't want to see well beyond resolution chop phantom canes outside certain regional forums. 

[Mike.Ventrice]

Per video previous page, GFS MJO may be a little fast, GEFS MJO members look to be getting to the right area, but look dampened.   Euro slower.  I'll keep my hopes up for June.  Just my impression of thread dynamics, its early now, people are pretty relaxed, but once well into the season, people won't want to see well beyond resolution chop phantom canes outside certain regional forums. 

 

This recent evolution where the MJO signal looks damped is due to an unfavorable superposition of the MJO active phase with local suppression forced by the convectively suppressed phase of a westward propagating equatorial Rossby wave. This will only be a temporary suppression, as the MJO should reappear in convection over the West Pacific. I think it will progress across the Atlantic-African sector during early June, in agreement with your assessment.

[Ground Scouring]

FWIW, vertical instability across the Trop Atl has been below avg thus far in 2013:

But instability in the Caribbean and in the Gulf of Mexico has been average this year, compared to below-average values in 2011-2012. That would signal an increased likelihood for development west of 60W. Also, the subtropics are more stable this year, meaning fewer higher-latitude systems are to be expected. As far as instability in the MDR is concerned, it is still higher than it was in 2011-2012 and is keeping pace with the mean (note the upward incline matching that of the mean). Also, based upon my response to HM, the factors (if I am reading them correctly) seem to favor this trend and likely favor average instability in the MDR during the peak season.

 

ts_al_car_THDV.gif

ts_al_gmx_THDV.gif

[bluewave]

But instability in the Caribbean and in the Gulf of Mexico has been average this year, compared to below-average values in 2011-2012. That would signal an increased likelihood for development west of 60W. Also, the subtropics are more stable this year, meaning fewer higher-latitude systems are to be expected. As far as instability in the MDR is concerned, it is still higher than it was in 2011-2012 and is keeping pace with the mean (note the upward incline matching that of the mean). Also, based upon my response to HM, the factors (if I am reading them correctly) seem to favor this trend and likely favor average instability in the MDR during the peak season.

 

ts_al_car_THDV.gif

ts_al_gmx_THDV.gif

 

The Caribbean instability has been peaking from the spring into the early summer before dropping off has we head into the heart

of the season during recent years. It's still too early to know if this will be the case again this season, but it will be interesting

to see how things play out.

 

2012

 

 

2011

 

 

2010

 

 

 

 

 

[Superstorm93]

I can hear the sighs of displeasure already...

 

 

 

The system north of Puerto Rico has surprisingly completed its "top down" process and now has a weak surface low (TAFB has it at 1012mb) with some shallow convection developing near the newly formed low. Shear really isn't a problem since the system is basically a hybrid right now, but if it starts developing tropical characteristics it should quickly get blown away. With that being said, sea surface temperatures are below the "magical number" for development with readings AOA 77-79 Fahrenheit and extremely dry air completely surrounding the former ULL.

 

Persistence has definitely been this systems greatest ally and unfortunately, I imagine if this develops any more than it already has, that we will see a STWO within the next 12 hours. Pressures are extremely high in the area and the environment is garbage so you can probably guess the outcome...

 

Short lived crap-invest is about all I see in this thing:

 

 

 

 

 

[Ground Scouring]

The Caribbean instability has been peaking from the spring into the early summer before dropping off has we head into the heart

of the season during recent years. It's still too early to know if this will be the case again this season, but it will be interesting

to see how things play out.

I think the instability declined during summer 2010-2012 due to the thermal expansion of the Saharan heat ridge, a consequence of the IOSD which I mentioned in my response to HM. But since the look of the IO (with a -, not +, IOSD this time) is different this year, I would expect a different, more favorable trend in the Atlantic...no?

[Ed Lizard]

Random question for the smart weather people and/or the history nerds.

 

 

Was Hurricane Audrey, the early season big Louisiana hurricane, (which, if I recall, people on this very forum in earlier years say Audrey may have been weakening to a Cat 1 at landfall) an analog of any type (TC possibly going to a warm seclusion XTC maybe) to Hurricane Sandy and New York/New Jersey?

[Srain]

Random question for the smart weather people and/or the history nerds.

 

 

Was Hurricane Audrey, the early season big Louisiana hurricane, (which, if I recall, people on this very forum in earlier years say Audrey may have been weakening to a Cat 1 at landfall) an analog of any type (TC possibly going to a warm seclusion XTC maybe) to Hurricane Sandy and New York/New Jersey?

 

Radar imagery loop of Audrey from Ellington AFB (Houston)

 

http://docs.lib.noaa.gov/rescue/mwr/085/mwr-085-06-0221.pdf

[Ed Lizard]

 

Radar imagery loop of Audrey from Ellington AFB (Houston)

 

http://docs.lib.noaa.gov/rescue/mwr/085/mwr-085-06-0221.pdf

 

 

What excitement we'd have had on the KHOU-TV 11 forum for that one.  If the internet had been invented, and if I had been born yet.

[phil882]

Quite an impressive system north of Puerto Rico... it looks like it won't have enough time transition over to a fully tropical entity, but it defiantly has a surface circulation and sufficient convection. Sorta surprised the NHC hasn't at least acknowledged it. 

 

http://www.atmos.albany.edu/student/ppapin/output/5_11_13/large_sat.html

 

Closeup > http://www.atmos.albany.edu/student/ppapin/output/5_11_13/sat.html

 

I'm going to take some time to try to explain how you can go from a upper-level cyclone that then transitions into a tropical cyclone through the "top-down" process that tropical meteorologists occasionally mention.

 

You can see the evolution in the large scale satellite animation above. There was a broad trough that exited florida on the dynamic tropopause, where anomalously high PV is located (stratospheric air) (In excess of +2PVU colored red). Upper level +PV anomalies can communicate with the lower levels of the atmosphere if the static stability of the atmosphere is low. Given that we are now entering the middle part of May, the static stability between 20-30N is decreasing given increased heating at the surface due to increased solar output warmest the lowest levels of the atmosphere. Another factor that contributes to decreased static stability is the depressed tropopause due to the upper level trough. If you decrease the height the minimum temperature of the atmosphere, while also increasing the temperature in the lowest levels of the atmosphere due to increased solar output, you increase the lapse rate in the entire atmospheric column, decreasing stability. Add a little bit of positive differential vorticity advection + upper level divergence on the left side of the upper-level disturbance and you have a recipe for convective development.

 

In order to understand how an upper-level circulation can work its way down to the surface, you need to use this convective argument through decreased static stability. When you have a large area of convective precipitation, it modifies the theta profile of the atmosphere, producing a diabatic heating anomaly in the mid-levels where precipitation releases latent heat converting from a liquid to a solid. The gradient of potential temperature anomaly dictates the potential vorticity anomaly, with +PV in the low-levels from this diabatic heating profile, and -PV in the upper-levels. The +PV in the low-levels is what leads to the developing low-level circulation that can then continue to develop through traditional WISHE TC genesis ideas.

 

So in the end way wave upper level cutoff cyclones help to develop tropical cyclone is like this:

 

Upper-Level +PV associated with cutoff --> Increased Lapse Rates --> Decreased Static Stability + Differential Vorticity Adv --> Large Area of Convective Precipitation --> Mid-Level +Potential Temperature Anomaly --> +PV in low-levels --> WISHE takes over or aids in TC development as upper-level cutoff decays due to -PV produced from Mid-Level +Potential Temperature Anomaly. 

 

I know a lot of people on here like to bash these type of tropical transition events as name wasters as systems that aren't very substancial. In the early portion of the season that is largely true. However, as we progress later in the season, this happens rather often (at least several times a year) and can lead to more substancial systems. Both Katrina and Rita (2005) had some degrees of "top-down" development thanks to the contribution of an upper level +PV anomaly that played a pivotal role in their genesis. Thus, they do have an important place in the TC world and probably play a larger % in the total number of TCs per year than currently acknowledged. 

[JonathanBelles]

I have one question regarding a possible contradiction in your thought process. When the upper trough moves through lowering the tropopause, you lower the level of minimum temperature, but you also increase that minimum temperature in doing so. That limits the increase in lapse rate, which should agreeably decrease stability. Can you explain this contradiction or am I missing the point?

[phil882]

I have one question regarding a possible contradiction in your thought process. When the upper trough moves through lowering the tropopause, you lower the level of minimum temperature, but you also increase that minimum temperature in doing so. That limits the increase in lapse rate, which should agreeably decrease stability. Can you explain this contradiction or am I missing the point?

 

With this thought experiment, I was assuming the minimum temperature at the troposphere remains constant. This is not necessarily true as you mention, since temperature at the tropopause could increase as the tropopause descends downward in height.

 

The key thing to understand in this case is that Lapse Rate is traditionally calculated between two different pressure levels... 

 

Lets just say that we want to calculate lapse rate from the surface to 500 hPa. Since the temperature minimum in the troposphere is at the tropopause, if we lower the tropopause from some typical pressure level (eg. 200 hPa) to a lower pressure level (500 hPa) then we would expect to have a steeper (greater) lapse rate between the surface and 500 hPa because we have lowered the temperature at 500 hPa. Even if we increase the temperature at the tropopause as it descends  the most important factor is if the temperature decreases at 500 hPa from before (when the tropopause was at 200 hPa) to after (when the tropopause drops to 500 hPa). Upper level lows are almost always associated with decreases in 500 hPa temperatures as they move overhead, which thus steepens the lapse rates in the low-mid levels of the atmosphere, which is the key point.

 

So in short... (sfc to 500 hPa) lapse rate steepen below the tropopause since temperatures at 500 hPa decreases as the tropopause drops. 

[Ed Lizard]

Looks like the surface low is getting farther from any convection.  Nice change of pace, anyway.

[MJO812]

2013 Hurricane Season from Accuweather

 

 

After a devastating blow to the East from Superstorm Sandy in October of 2012, residents and homeowners on the Atlantic coast should anticipate another active season in 2013.The biggest concerns for the upcoming season include development in the Gulf of Mexico, an impact in Florida and also another East Coast impact.

 

 

 

 

http://www.accuweather.com/en/weather-news/atlantic-hurricane-forecast-2013/12116274

[icebreaker5221]

Quite an impressive system north of Puerto Rico... it looks like it won't have enough time transition over to a fully tropical entity, but it defiantly has a surface circulation and sufficient convection. Sorta surprised the NHC hasn't at least acknowledged it. 

 

http://www.atmos.albany.edu/student/ppapin/output/5_11_13/large_sat.html

 

Closeup > http://www.atmos.albany.edu/student/ppapin/output/5_11_13/sat.html

 

I'm going to take some time to try to explain how you can go from a upper-level cyclone that then transitions into a tropical cyclone through the "top-down" process that tropical meteorologists occasionally mention.

 

You can see the evolution in the large scale satellite animation above. There was a broad trough that exited florida on the dynamic tropopause, where anomalously high PV is located (stratospheric air) (In excess of +2PVU colored red). Upper level +PV anomalies can communicate with the lower levels of the atmosphere if the static stability of the atmosphere is low. Given that we are now entering the middle part of May, the static stability between 20-30N is decreasing given increased heating at the surface due to increased solar output warmest the lowest levels of the atmosphere. Another factor that contributes to decreased static stability is the depressed tropopause due to the upper level trough. If you decrease the height the minimum temperature of the atmosphere, while also increasing the temperature in the lowest levels of the atmosphere due to increased solar output, you increase the lapse rate in the entire atmospheric column, decreasing stability. Add a little bit of positive differential vorticity advection + upper level divergence on the left side of the upper-level disturbance and you have a recipe for convective development.

 

In order to understand how an upper-level circulation can work its way down to the surface, you need to use this convective argument through decreased static stability. When you have a large area of convective precipitation, it modifies the theta profile of the atmosphere, producing a diabatic heating anomaly in the mid-levels where precipitation releases latent heat converting from a liquid to a solid. The gradient of potential temperature anomaly dictates the potential vorticity anomaly, with +PV in the low-levels from this diabatic heating profile, and -PV in the upper-levels. The +PV in the low-levels is what leads to the developing low-level circulation that can then continue to develop through traditional WISHE TC genesis ideas.

 

So in the end way wave upper level cutoff cyclones help to develop tropical cyclone is like this:

 

Upper-Level +PV associated with cutoff --> Increased Lapse Rates --> Decreased Static Stability + Differential Vorticity Adv --> Large Area of Convective Precipitation --> Mid-Level +Potential Temperature Anomaly --> +PV in low-levels --> WISHE takes over or aids in TC development as upper-level cutoff decays due to -PV produced from Mid-Level +Potential Temperature Anomaly. 

 

I know a lot of people on here like to bash these type of tropical transition events as name wasters as systems that aren't very substancial. In the early portion of the season that is largely true. However, as we progress later in the season, this happens rather often (at least several times a year) and can lead to more substancial systems. Both Katrina and Rita (2005) had some degrees of "top-down" development thanks to the contribution of an upper level +PV anomaly that played a pivotal role in their genesis. Thus, they do have an important place in the TC world and probably play a larger % in the total number of TCs per year than currently acknowledged. 

 

 

Great discussion Phil!     I generally think more in terms of the thermodynamics, but they essentially explain the same process.  I.e., top-heavy mass flux profile in presence of pre-existing mid-level vortex -> UL warming (warm core development + LH release) + LL cooling (cold core development below vorticity maxima + evaporative cooling) -> shallower CAPE profile -> bottom-heavy mass flux profile -> lower level of maximum LH release -> lower maximum vertical gradient of diabatic heating -> lower level of PV production -> LL cyclone develops.  The key is that the vertical derivative of mass flux, d(rho*w)/dz, is (by continuity) directly proportional to the horizontal convergence of the wind.  Therefore, the lowering of the maximum vertical acceleration requires convergence in an environment with pre-existing cyclonic vorticity, leading to a consolidation of vorticity near the center of the cyclone.  The suppression of lateral export of moist entropy is a convenient positive feedback.

 

Also, you'd be hard pressed to find many (if any) genesis cases where the mid-level vortex doesn't strengthen before the low-level vortex, which was traditionally refered to as "top down" (just a few recent examples: observations: Nolan and McGauley 2012, Raymond and Lopez 2011, Raymond et al. 2011, Komaromi 2013, as well as hi-res idealized simulations: Nolan 2007, Rappin and Nolan 2012).  The original Bister and Emanuel (1997) and Simpson et al. (1997) concept of vorticity vertically penetrating downward in the presence of net +w simply doesn't happen, but the terminology, and the necessity of a mid-level vortex prior to genesis appears to be robust.  Actually, now I'm thinking that maybe your phraseology is more relevant to tropical transition (cold core UL low -> warm core low) than the traditional definition of top-down?

 

I might also add that just because the formation of a robust mid-level vortex is almost always a pre-requisite doesnt mean that bottom-up mechanisms (VHTs) are not simultaneously helping to spin up the vortex.  The LL circulation and ML circulation are almost always displaced prior to genesis, and its most likely a combination of top-down mecahnisms in the viscinity of the MCV and bottom-up processes in the viscinity of the LL vortex that gradually results in the vertical alignment of the two... ultimately culminating in genesis. 

[am19psu]

Anyone know if ESRL is going to run the HFIP GFS EnKF models again this season? They were quite valuable last year.

[Ed Lizard]

Pre-season primer from our friends at Capital Weather Gang.  Did I mention 2003, if it works as an analog for 2013, would make for an exciting season.  I never lurk the MA or SE subforums outside of snow and severe season.  DT weighs in on the comments as well.

 

http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2013/05/17/atlantic-hurricane-season-2013-whats-new-and-what-should-we-expect/

[dtk]

Anyone know if ESRL is going to run the HFIP GFS EnKF models again this season? They were quite valuable last year.

There will be another HFIP-supported GFS near-real time demo again this year.  I only know the plans for the deterministic component (with hybrid EnVar analysis update).....and I'm unsure what they plan to run in terms of global ensembles (GFS, FIM, or otherwise).

 

It will be a bit different than last year as they are becoming more aligned with our target GFS/GDAS implementation for FY14.  They will be using the Semi-Lagrangian dynamic core (not Eulerian), different resolution than last year, different parameters and/or physics, and a slightly different DA configuration.  I can share some of the specifics offline if you're interested...though it is in the early stages of being put together.

[Eyewall2005]

Boy would i have loved to be around...

 

[icebreaker5221]

Boy would i have loved to be around...

 

 

 

Two particularly amazing subsets of those time periods:

 

0 MH in 26 seasons (1966-1991)

7 MH in 7 seasons (1944-1950)

[am19psu]

First five days of June might be interesting in the Western Caribbean. There will be a col set up over top the monsoon trough. A Kelvin wave ought to be moving through the area during that period as well. Might just be enhanced rainfall but conditions will be favorable for some sloppy mess to spin up.

[Mike.Ventrice]

The 850 hPa zonal wind anomaly hovmoller averaged about the equator shows the CCKW Adam is referring to. In a roughly 5-7 days, watch for the lower tropospheric easterly wind phase of the Kelvin wave to increase the trades over the Atlantic, as well as over Africa. I'm thinking we might get a good SAL outbreak here, as an extra-tropical trough looks to dig southward over northwest Africa and disrupt the Saharan Heat Low, forcing it to break and progress westward over the north tropical Atlantic. Too bad it's not August or September, I'd be very giddy for some MDR activity here.

 

[HM]

As usual, a great explanation. I am examining the latest trends in the IOSD and the early-summer monsoonal convection over the Punjabi regions to determine whether an enhanced anticyclone will be present near the southern Indian subcontinent this boreal summer. Based upon OI SSTA, the +IOSD regime in April 2010-2012, with a lag through MJJ period, seems to have been a factor in the increased subsidence / reduced vertical instability in the Eastern Atlantic since 2010, mainly but not solely due to the influx of a very stable Saharan air mass / heat ridge. In the following image, the +IOSD is very evident due to the strong warm anomaly over the SW Indian Ocean, which means a somewhat cooler IO / stronger temperature gradient north of the equator, which leads to an enhanced summer monsoon over the Punjab.

 

 

Unsurprisingly, the SSTA gradient supported strong +OLR over the Arabian Sea just N of the equator:

 

 

Note the enhanced low-level trades / 700-mb anticyclone over the N Indian Ocean, along with the enhanced monsoonal westerlies near 5-10N 60E, in this composite from the same period:

 

 

This year, however, the IOSD in the austral winter appears to have gone sharply negative. The April 2013 OI SSTA shows a sharp reversal over the SW Indian Ocean, with cooler anomalies predominating over the N IO basin, thereby resulting in a suppressed or delayed Punjabi monsoon this summer.

 

 

The 700-mb anomalies in April 2013 show prevailing westerlies dominating the N IO basin, a sharp reversal from April 2010-2012:

 

 

I would say that all these factors point to a more-unstable Atlantic basin than what we have been seeing, relatively, since 2010. I do know that the GLAAM has been unfavorable for the Atlantic recently and, despite a recent dip in April, has been sharply on the increase this month. Nevertheless, is not such a strongly positive variation often a precursor to an unstable GLAAM regimen rather than a sustained + regimen? Am I on the right track?

 

As far as the IOSD, I agree that we peaked a negative event this past winter. The -IOSD developed sometime between October to November 2012 and really bottomed out in January. This will lag through the warm season and has already influenced the development of a -IOD. This is one reason why El Niño may not develop this warm season (but of course not the only factor).

 

In 2010, we went from a -IOSD to the development of a +IOSD by the summer (just in time for hurricane season). First year La Niña wave after El Niño and its implication on the AMO/TNA certainly made it an active hurricane season in the Atlantic. But notable periods of stability were showing up, despite these other factors.

 

The +IOSD peaked in 2011 to the point that the entire southern Indian Ocean slowed down post-peak (exceptionally warm water developed from the SE Atlantic into the entire IO with currents almost stopped by the enhanced easterlies over the circumpolar/south indian flows).  This is when the IO Hadley Cell really went crazy and never looked back. The IOSD basically lingered positive with the anomalies drifting west for most of 2012. It was the IOD that became more coherent and dominate (it actually went positive in 2011 but continued to climb and grow most anomalous in 2012's summer).

 

2011 was so warm; the IOD and the IOSD were both positive! That was incredible. That basic formula held again last year but the IOD was even stronger while the IOSD was more of a lingering thing.

 

It is safe to say we have passed this period and combination of factors. The stability will likely not be as bad as 2011 and 2012.

[Ground Scouring]

As far as the IOSD, I agree that we peaked a negative event this past winter. The -IOSD developed sometime between October to November 2012 and really bottomed out in January. This will lag through the warm season and has already influenced the development of a -IOD. This is one reason why El Niño may not develop this warm season (but of course not the only factor).

 

In 2010, we went from a -IOSD to the development of a +IOSD by the summer (just in time for hurricane season). First year La Niña wave after El Niño and its implication on the AMO/TNA certainly made it an active hurricane season in the Atlantic. But notable periods of stability were showing up, despite these other factors.

 

The +IOSD peaked in 2011 to the point that the entire southern Indian Ocean slowed down post-peak (exceptionally warm water developed from the SE Atlantic into the entire IO with currents almost stopped by the enhanced easterlies over the circumpolar/south indian flows).  This is when the IO Hadley Cell really went crazy and never looked back. The IOSD basically lingered positive with the anomalies drifting west for most of 2012. It was the IOD that became more coherent and dominate (it actually went positive in 2011 but continued to climb and grow most anomalous in 2012's summer).

 

2011 was so warm; the IOD and the IOSD were both positive! That was incredible. That basic formula held again last year but the IOD was even stronger while the IOSD was more of a lingering thing.

 

It is safe to say we have passed this period and combination of factors. The stability will likely not be as bad as 2011 and 2012.

Thanks so much for the very detailed response...it is good to see that my views were in line with what you were seeing. I have also noticed that the E Pacific seems to be especially responsive to surface wind stress late in meteorological spring. For instance, in the 10-day period before our recent Kelvin wave crossed 120˚W, a period of -OLR / increased trades due to an enhanced Hadley in the SE Pacific was enough to cool NINO 1-2 by a good several degrees (May 1-10 period). The lag continued for the next several days even as the Kelvin wave-induced + U-anomalies at 250 mb migrated eastward. This trend, whose feedback loop will also serve to reinforce the SE Pacific Hadley, is yet another factor that will slow the advance of warm subsurface anomalies, especially without an "active" MJO signal. The latent (meaning enhanced but not "true") MJO signal, which supports a feedback favoring a slow N-PAC SSTA progression to a more neutral PDO configuration, looks to last into most of the first half of June or perhaps beyond. This should produce, in my view, a more typical early start to the Atlantic season, meaning fewer prospects of early development before the start of July. At least that is how I see it, but please feel free to voice your assessment/corrections.

[hurricaneman]

The models are predicting some sort of development, but if I'm being honest I think not much is going to come of it if that shear remains where it is, if the MJO enters phase 8 or 1 like the GFS says which is starting to look like it won't happen there could be an invest in June but I really don't expect anything developing until July when the pattern changes towards a summer pattern

[klw]

Saw this in an article on the Goes failure:

http://www.accuweather.com/en/weather-news/american-weather-satellite-fails-again/13038942

It could take several weeks before GOES-14 to be moved into optimal position for coverage of the Western Atlantic Basin with the approach of the hurricane season. AccuWeather.com meteorologists suspect that a tropical system may form in the neighborhood of the Gulf of Mexico during the first part of June.

[Srain]

In its 2013 Atlantic hurricane season outlook issued today, NOAA’s Climate Prediction Center is forecasting an active or extremely active season this year.

For the six-month hurricane season, which begins June 1, NOAA’s Atlantic Hurricane Season Outlook says there is a 70 percent likelihood of 13 to 20 named storms (winds of 39 mph or higher), of which 7 to 11 could become hurricanes (winds of 74 mph or higher), including 3 to 6 major hurricanes (Category 3, 4 or 5; winds of 111 mph or higher).

These ranges are well above the seasonal average of 12 named storms, 6 hurricanes and 3 major hurricanes.

 

http://www.noaanews.noaa.gov/stories2013/20130523_hurricaneoutlook_atlantic.html