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HurricaneJosh

Atlantic Tropical Action 2013

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We probably need more research to know for sure.

 

http://www.wunderground.com/blog/JeffMasters/archive.html?year=2012&month=11

 

Unusually stable air over the Tropical Atlantic in 2012

For the third consecutive hurricane season, 2012 featured an unusual amount of dry, sinking air over the tropical Atlantic and Caribbean Sea. Due to warmer-than-average sea surface temperatures and an active African Monsoon that generated plenty of African waves, a remarkably high number of tropical storms managed to form, but the unusually stable air in the hurricane genesis regions made it difficult for the storms to become strong. When we did see storms undergo significant intensification, it tended to occur outside of the tropics, north of 25°N, where there was not as much dry, sinking air (Sandy's intensification as it approached landfall in Cuba was an exception to this rule.) If we look at the last nine hurricane seasons (Figure 2), we can see that the hurricane seasons of 2010, 2011, and 2012 all featured similar levels of highly stable air over the tropical Atlantic. This is in marked contrast to what occurred the previous six years. The past three seasons all featured a near-record number of named storms (nineteen each year), but an unusually low ratio of strong hurricanes. Steering patterns the past three years also acted to keep most of the storms out to sea. Is this strange pattern something we'll see more of, due to climate change? Or is it mostly due to natural cycles in hurricane activity? I don't have any answers at this point, but the past three hurricane seasons have definitely been highly unusual in a historical context. I expect the steering currents to shift and bring more landfalling hurricanes to the U.S. at some point this decade, though.

 

I think the best example of this was Hurricane Isaac last year. Clearly, Isaac could have been a Georges-type major Caribbean/Gulf crusier but the dry air really messed with it's inner core.

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I think the best example of this was Hurricane Isaac last year. Clearly, Isaac could have been a Georges-type major Caribbean/Gulf crusier but the dry air really messed with it's inner core.

not really, the fact that Cuba and Hispaniola were there were the real culprits

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not really, the fact that Cuba and Hispaniola were there were the real culprits

Isaac sucked in dry air off Cuba and Hispaniola and was never able to mix it out fully prior to landfall. Land interaction solely hardly messed up its core.

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Isaac sucked in dry air off Cuba and Hispaniola and was never able to mix it out fully prior to landfall. Land interaction solely hardly messed up its core.

 

 

Storms with large cores in general deepen much slower and have a much harder time maintaining symmetry.   Exception being annular storms, but those don't usually form rapidly .

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But why? I thought that the SIOD was more favorable for instability this year. May HM et al. chime in on this?

 

 

HM could probably give the better answer, but in short, until recently, the MDR had been under +VP (200 mb velocity potential) almost continuously since June 1!  This results in a lot of warm, dry subsidence.  No doubt this has contributed to lower instability. 

 

See here:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ir_anim_monthly.shtml

 

Looks like as the MJO approaches phase 1, we're seeing enhanced 200 mb neg velocity potential over the east Pac, and starting to see it reach the Gulf and Caribbean too. 

 

post-378-0-13997000-1372383990_thumb.gif

 

Gulf has been first to respond, with a recent uptick in instability. 

 

post-378-0-44601400-1372384019_thumb.gif

 

Extrapolating forward, I suspect instability will increase over the MDR soon too as conditions become more favorable for upward motion. 

 

post-378-0-51649800-1372384098_thumb.png

 

But remember, as HM so eloquently noted last week, it's not until after the MJO is exiting phase 1 or in phase 2 that the Hadley cell relaxes, shear decreases, and conditions become more favorable for genesis. 

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Is it time for some banter? A really nice MJO/CCKW pulse across the Western Hemisphere-Indian Ocean and nothing in the models in the sense for tc genesis over the Atlantic. Could the strong MJO over the western and central Pacific have caused too much influence on the extra-tropical wave guide that would allow for such an anomalous trough to push down the eastern U.S. next week and cause too much upper-level westerly flow over the Atlantic? 

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I maintain that just looking at the phase of the MJO by itself yields little help as far as tropical genesis chances in the Atlantic overall. I base this on a study of storms going back over 35 years. The number of storms generated is fairly flat when comparing supposedly favorable phases with supposedly unfavorable phases. If anyone doubts this, just do the statistical

analysis yourself. This post isn't directed at anyone in particular.

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I maintain that just looking at the phase of the MJO by itself yields little help as far as tropical genesis chances in the Atlantic overall. I base this on a study of storms going back over 35 years. The number of storms generated is fairly flat when comparing supposedly favorable phases with supposedly unfavorable phases. If anyone doubts this, just do the statistical

analysis yourself. This post isn't directed at anyone in particular.

 

Its a helpful tool to identify when chances increase or decrease for TC formation. But favorable phases are no

guarantee for development, and storms do form in unfavorable phases. So when people say the MJO is headed

for phases 1-2, its a window of time to watch for development. Other factors obviously come into play which

determine the final outcome of TC genesis. For example, we were discussing the favorable MJO potential

for development when Sandy formed last year.

 

http://typhoon.atmos.colostate.edu/Includes/Documents/Publications/klotzbach2010.pdf

 

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I maintain that just looking at the phase of the MJO by itself yields little help as far as tropical genesis chances in the Atlantic overall. I base this on a study of storms going back over 35 years. The number of storms generated is fairly flat when comparing supposedly favorable phases with supposedly unfavorable phases. If anyone doubts this, just do the statistical

analysis yourself. This post isn't directed at anyone in particular.

 

 

Its a helpful tool to identify when chances increase or decrease for TC formation. But favorable phases are no

guarantee for development, and storms do form in unfavorable phases. So when people say the MJO is headed

for phases 1-2, its a window of time to watch for development. Other factors obviously come into play which

determine the final outcome of TC genesis. For example, we were discussing the favorable MJO potential

for development when Sandy formed last year.

 

http://typhoon.atmos.colostate.edu/Includes/Documents/Publications/klotzbach2010.pdf

 

attachicon.gif201210.phase.90days.gif

 

Agreed guys, every MJO events just provide a time-frame where we may see an increase of genesis. 

 

You need to normalize you genesis events per MJO phase during summer since there an uneven number of MJO days per phase in the climo. By doing so,  you will see favorbale phases during 1-3, unfavorable during 6-8. What is important IMO is where the atmospheric Kelvin wave compontent of the MJO is as well. But you tend to see the increased Atlantic genesis when the MJO is back over the Indian Ocean, and currently it's still very suppressed there. Give it a week.

 

Also, the standard MJO index tends to have a lot of noise and not will also show a coherent MJO event when there is one, or vice versa will show an MJo event when there isn't one! The RMM index also misses a good deal of boreal summer MJO events (current research that should be published in some time if I can get around to revisions). 

 

I prefer the VP200 space-time filtered techinque, which clearly shows the center of the upper-level divergent branch of the MJO over the East Pac = increased shear over the Atlantic in the short range, which should begin to relax soon thereafter.

 

28.gif

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I definitely did normalize the genesis events per MJO phase during summer since there are an uneven number of MJO days per phase in the history. I definitely thought about that. So, that didn't skew the results.

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While absolutely nothing is going on in model land...

 

I really do find it interesting how beefy the tropical waves have been so far this June. With ECMWF, CFS, and now even the GFS Ens showing a favorable pattern for possible tropical cyclone genesis in the central Atlantic by mid-July or so, we might actually see a decent system or two come out of this pattern. 

 

There is currently a very impressive tropical wave approaching the islands that would probably develop into a tropical cyclone if it were a month later in the season. The GFS shows this wave bypassing south America and making it's way into the western Caribbean where it becomes part of a large soupy mess that seems to be enhanced somewhat by the upward motion in the east Pacific. This is what the over-zealous CMC was trying to develop into a hurricane a few days ago. 

 

 

 

And just for kicks, there's also another very strong tropical wave located over western Africa that should exit within two days. 

 

(850mb vorticity and streamlines) 

 

 

If the Bermuda high remains as strong and as dangerous as it is now when the peak season rolls on in, Josh should probably have footage of at least one system to look forward to. 

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Edit: Speak of the devil and he shall appear

 

(I would say lame lemon, however this wave is mildly interesting) 

 

1. SHOWERS AND THUNDERSTORMS HAVE INCREASED THIS MORNING IN ASSOCIATION
WITH A TROPICAL WAVE A FEW HUNDRED MILES EAST OF THE LESSER
ANTILLES. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR DEVELOPMENT...
AND THIS SYSTEM HAS A LOW CHANCE...NEAR 0 PERCENT...OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WEST-
NORTHWESTWARD AT 20 TO 25 MPH. REGARDLESS OF DEVELOPMENT...GUSTY
WINDS AND LOCALLY HEAVY RAINS ARE EXPECTED TO SPREAD ACROSS THE
LESSER ANTILLES AND NORTHEASTERN VENEZUELA LATER TODAY AND TONIGHT.

 

Such a tease though. This thing is textbook for Caribbean development. 

 

Oh well. The waiting game begins once again. 

 

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^^ A week after the resolution reduction (day 16), the op GFS is nothing more, really, than just another ensemble perturbation, but a sign of life, a closed 700 mb low moving WNW and approaching Central America, with 500 mb and 700 mb weakness potentially opening a path towards the Northern or Eastern Gulf Coast.  Or not.

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As mentioned in the TX/MX/NM/LA thread a day or two ago, a tropical wave is progressing W approaching the Lesser Antilles. MIMIC is suggesting the surge of tropical moisture will continue to move W to WNW over the next 4 days. There is some potential as the ensemble guidance has suggested that a weak tropical system could develop next week in the Bay of Campeche as this area of disturbed weather enters the Western Gulf.

 

latest72hrs.gif

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I strongly believe that the upcoming days are going to provide very interesting prospects for tropical development close to home, in the NE Gulf of Mexico. Currently, we have a very amplified trough that will induce height falls from the TN Valley southward into the Gulf and the NW Caribbean Sea, where we are already seeing low pressures related to a weak monsoonal trough which are being enhanced by the incoming CCKW. There is a very strong band of moisture convergence and a pronounced low-level jet extending around the west flank of the strong Bermuda High and will provide a broad band of ample low-level moisture streaming northward from Central America into the NE Gulf. As this happens, watch for enhanced low-level convergence beginning in about three days as the trough axis digs down. Initially, I do not expect rapid development due to shear, but as the CCKW / MJO signal moves in, the amplified pattern will begin to modulate as the subtropical Hadley cell expands northward and the flow becomes more zonal; thus the trough axis will pull out beginning by day five, allowing shear to decrease gradually and to shift the mean flow to the SSE. This is a classic medium-range set-up in which a departing upper-level trough will leave sufficient height falls and convergence, thereby favoring a weak surface low over the NE Gulf and then possible tropical development after day five, especially as heights rise (i.e. TS Edouard 2008). This is the time of year (June-July) in which N-Gulf systems tend to develop near decaying frontal boundaries and can spin up quite quickly in some cases, like the 1943 Surprise Hurricane. And the GFS and the ECMWF are already hinting at this type of development as the MJO signal moves in. So all in all, SE TX, LA, and MS may need to keep watch very soon.

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I definitely did normalize the genesis events per MJO phase during summer since there are an uneven number of MJO days per phase in the history. I definitely thought about that. So, that didn't skew the results.

 

Interesting. I'm sorry if I came across aggressive- was in a hurry this morning as I wanted to talk a bit more about this than hit my deadlines on my forecasts.

 

I'd love to see some of your results if you don't mind sharing :)

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Just a reminder if you entered the tropical season contest that your July monthly forecast is due, we're using the same thread as June and I just bumped it to the top. 

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If SSTA were to increase, as appears certain, across NINO 3, 3.4, and 4, would not the East Pacific Hadley cell tend to shift east as the tropical forcing migrates from Indonesia nearer to the International Date Line? The warming, if any, will likely coincide with the peak of the hurricane season. I would tend to think that a corresponding rise in heights would spread northeast into the Caribbean and the SW Atlantic, thereby elongating the Bermuda High from east to west and shifting the mean ridge farther west into the Southeast United States. That would tend to serve as a block and regionally increase the hurricane threat to South FL and the Central Gulf Coast (MS / LA). I have seen various indications showing that during neutral-warm years with a “Modoki”-type SSTA configuration and a negative IOD, the Bermuda High tends to shift farther south and west, thus preventing cyclones from curving into the Carolinas and forcing them west into FL and the Gulf. Historically, South FL has seen several of its strongest hurricanes during this type of set-up, i.e. 1919, 1928, (perhaps 1929 and 1935), and 1965 (2004 mainly affected Central FL but also featured this set-up).

 

NOAA SST dataset, ERSSTA 3b:

 

http://nomads.ncdc.noaa.gov/las/getUI.do

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The Euro is relatively quiet the next ten days. The main problem is that the areas of convection

over the Gulf will have too much shear to allow development with the trough digging into the Central

States.

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The Euro is relatively quiet the next ten days. The main problem is that the areas of convection

over the Gulf will have too much shear to allow development with the trough digging into the Central

States.

My personal feeling is that most development will wait until August. This year has many hallmarks of a late-bloomer--unlike the past several years, which featured an active start and a relatively dull peak.

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My personal feeling is that most development will wait until August. This year has many hallmarks of a late-bloomer--unlike the past several years, which featured an active start and a relatively dull peak.

 

That has been the main pattern the last few years with stronger developments holding off until August. But we'll see

if we can get a system or two to develop in mid to late July.

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Few of the GFS runs post lobotomy start trying to close a 700 mb low in the SW Caribbean in 2 weeks.

 

I should go revise my July contest numbers though, 2/1/0 is a touch optimistic.

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The 12zGFS shows signs of life at day 10 in the central Caribbean and sends it as a 993 low into northern Mexico at the end of the run, even the 0zEuro shows lowering pressures at day 10 so the Caribbean is the place to watch the next 9 to 12 days for development

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 A little bit sooner than the long range noise, the NCEP Ensembles are keying in on cyclogenesis in the Bay of Campeche during the 4th of July Holiday period. Upper level conditions should become a bit more conducive for development as the Bermuda Ridge builds back into the EasternGulf and a stalled boundary lingers across the Western Gulf. Increased tropical rains appear likely for the Mexican/Texas and Louisiana Gulf Coastal areas.

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I think the idea of Chantal in the Bay of Campeche seems probable if the model trends continue. Overall, however, most hurricane seasons sometimes don't even have a single storm until August. Even 2004 didn't give us Alex until the final day of July.

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I see the disturbed weather on the models, but I don't see any real suggestions of tropical cyclone development the next week the next week.  I see the GFS try to get something in the BoC, but it doesn't really get there.  I don't know what the NCEP TC probabilities key off of, but I see only a couple of 12Z GEFS manage a closed 1008 mb low, and I don't think any of the 18Z GEFS do so.  Euro almost gets there, but right on the coast.


 


Unless the 12Z NavGem scores the coup, I see, at best, a depression, maybe a minimal TC that moves inland quickly.


 


Euro has a wave entering the Gulf across Florida in 9-10 days, although that doesn't look to be in any hurry to develop. 12Z and 18Z GFS seem to see the 700 mb reflection of that at the resolution reduction.   I'm a little curious what individual ensemble Euro members do with that wave.  But at 240 hours, on the Euro, it isn't all that well developed and only a day or two from land.


 


Assuming that doesn't develop, and nothing is screaming it will, I think we'll get to MJO Phase 4 w/o a named tropical storm.


 


 


Euro wave as seen on hour 192 GFS 700 mb product before resolution, East of Florida at that time. Below.


post-138-0-90522400-1372642033_thumb.gif

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We appear to be headed into the typical July Slump. Other than 2005, and last years derecho, there is rarely any interesting weather at this time of year. Just gotta find something to do until probably mid August. GFS keeps the Caribbean and gulf pretty wet so there's a chance of something forming. I'm not optimistic it will be anything more than a name waster though.

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