2015 indicators: Instability / SST's / MSLP / Steering / Sal

[Andrew92]

There's another front emerging off the east coast this week? I would watch that. So far all three storms have originated from non-tropical sources, so those would be what to watch. Stalled fronts, troughs and MCS's all have that potential. A storm like Hurricane Bob (1991) wouldn't be impossible later in the season either.

Agreed the Gulf of Mexico could produce some late (for the Gulf) season surprises.

When it happened in 1997, 2002, and 2006, it didn't happen just once, all three instances. When looking prior to the middle of August, when things typically ramp up. 1997 had four storms off the East Coast in July as it is fair to count Danny even though it didn't form there but did re-develop. 2002 had Arthur and Cristobal (in early August, why I am going until about August 15 here), while 2006 had an unnamed storm and Beryl. Claudette has happened and given this recent history, this remains a good spot to look for development this time of year.

Also, regarding Invest 93L, it may not develop, but consider this often overlooked detail about 1997: there was a weak depression near the Caribbean that failed to develop further. There was also Chris in 2006 in a similar area, but El Nino was weaker and not as well-established that year as this year.

-Andrew92

[ninel conde]

As August arrives so arrives the winter-like east coast trof

[tolakram]

As August arrives so arrives the winter-like east coast trof

How does the temperature map, showing -5 to -6 near the Ohio Valley, predict an east coast trough?

This seems to show it better:
http://www.cpc.ncep.noaa.gov/products/people/mchen/CFSv2FCST/monthly/images/CFSv2.z700.20150726.201508.gif

[NDG]

Why would it matter much if the pattern will be an east coast trough or not, there will be nothing coming from the deep tropics other than Saharan Dust

[wxman57]

Why would it matter much if the pattern will be an east coast trough or not, there will be nothing coming from the deep tropics other than Saharan Dust

It matters because disturbances that track north of the Caribbean will find a more favorable environment for development. That's where most of this season's hurricanes will form. If there is a trof along the East U.S. Coast then those hurricanes will most likely recurve east of the U.S. Without the trof, the East U.S. Coast is open for a potential impact.

[TheStormExpert]

I posted this yesterday in the Global Models Thread, might as well post it here also.

Last two tweets are what caught my attention.

Interesting tweets from HurricaneTracker App about how the pattern is favorable for possible U.S. impacts from the East IF a Tropical Wave can survive the LONG trip across the lake.

@hurrtrackerapp
Development chances are down to almost nothing near FL. Some nice rains in store for the Sunshine state over the next several days. #flwx
10:39 AM - 26 Jul 2015

@hurrtrackerapp
As we enter early Aug, we will be looking to see if any strong waves make it through the hostile Atlantic. The Cape Verde season is upon us.
10:41 AM - 26 Jul 2015

@hurrtrackerapp
Too much northerly shear and dry air pushing in with no upper level divergence. No development for now near FL. #tropics
10:46 AM - 26 Jul 2015

‏@hurrtrackerapp
The door is open for landfall in early Aug IF any strong ATL waves make it through. High pressure in the W ATL may block any recurves.
10:51 AM - 26 Jul 2015

@hurrtrackerapp
Here is the pattern that models show for early Aug. Stronger trop waves pushing W underneath a ridge will be watched.
10:59 AM - 26 Jul 2015

[SFLcane]

Why would it matter much if the pattern will be an east coast trough or not, there will be nothing coming from the deep tropics other than Saharan Dust

It matters because disturbances that track north of the Caribbean will find a more favorable environment for development. That's where most of this season's hurricanes will form. If there is a trof along the East U.S. Coast then those hurricanes will most likely recurve east of the U.S. Without the trof, the East U.S. Coast is open for a potential impact.

Chris and what pattern do u foresee in the coming weeks in particular for us in Florida as we get closer to "busy" part of season if iam allowed to say that. :0(

[ninel conde]

Why would it matter much if the pattern will be an east coast trough or not, there will be nothing coming from the deep tropics other than Saharan Dust

Speaking of dust:

http://moe.met.fsu.edu/cgi-bin/gfstc2.c ... hour=180hr

as long as that pattern is locked in there will be no cape verde season. Perfect set-up to swamp the tropics with a flood of non-stop bone dry saharan dust.

[WPBWeather]

Why would it matter much if the pattern will be an east coast trough or not, there will be nothing coming from the deep tropics other than Saharan Dust

Speaking of dust:

http://moe.met.fsu.edu/cgi-bin/gfstc2.c ... hour=180hr

as long as that pattern is locked in there will be no cape verde season. Perfect set-up to swamp the tropics with a flood of non-stop bone dry saharan dust.

Now now. No pattern is ever "locked." SAL and shear can (and have) appeared and vanished within hours.

[ninel conde]

in active seasons, yes. that pattern has already been locked for sometime.

[SouthDadeFish]

I made this plot yesterday. It is 500 hPa vertical velocity (units are Pascals per second so positive values imply sinking motion) over the past 30 day period from 1979-2015 via the CFSR. The region of focus is between 10-20N and 80-30W. It shows the past two seasons have had the most subsidence over the ATL Main Development Region since 1979.



This subsidence results in a lot of dry air. I think dry air produced by subsidence is often times confused with SAL. Some studies have shown that subsidence is they key feature in producing dry air over the Atlantic, particularly the Eastern Atlantic. Although the above plot is only for a particular 30 day period early on in the ATL TC season, it shows that conditions have not been conducive to TC development in regard to thermodynamics. This is a big reason why the MDR is currently so dry.

It should be noted I made similar plots using the ERA Interim (not shown) and results were slightly different, but kept the same main idea. Although I did not have 2015 data, 2014 still had the most subsidence, with 1994 close behind. This also suggests we have been seeing record amounts of sinking motion across the ATL MDR over the early portion of the past two hurricane seasons.

[Ntxw]

Thanks for the plot and information SouthDadeFish. Sal and dust can be eroded with good waves pretty easily so dry air is differed much agreed. Higher than normal pressures is a big problem because as we know higher pressures means sinking air. Like on land, ridges of high pressures bring heat, drought, and persistent dry weather underneath. What is the cause of the persistent higher pressures across the Atlantic for the past few years?

[TheStormExpert]

Environment starting to improve some?

@EricBlake12: African dust is forecast to really diminish in the western Atlantic basin after the weekend. Maps @RyanMaue #climate http://t.co/bkhpslg6E4

[MGC]

Lots of dry air out over the MDR and CV regions. Was just checking the SST in the Atlantic and Caribbean. Around 81F in the Atlantic and 83-84 in Caribbean. GOM is the hot spot. 90F off Key West, 86-87F most rest of GOM. Need to keep storms out of the gulf......MGC

[ninel conde]

Lots of dry air out over the MDR and CV regions. Was just checking the SST in the Atlantic and Caribbean. Around 81F in the Atlantic and 83-84 in Caribbean. GOM is the hot spot. 90F off Key West, 86-87F most rest of GOM. Need to keep storms out of the gulf......MGC

no need for concern. as in the last few years the huge heat ridge has appeared over Texas once again. GOM should be quite safe. Back in May it seemed like this year MIGHT allow some GOM development, but that has changed back to the semi-permanent east coast trof.

[chaser1]

"....Was just checking the SST...GOM is the hot spot. 90F off Key West, 86-87F most rest of GOM. Need to keep storms out of the gulf......MGC

no need for concern. as in the last few years the huge heat ridge has appeared over Texas once again. GOM should be quite safe. Back in May it seemed like this year MIGHT allow some GOM development, but that has changed back to the semi-permanent east coast trof.

Really? So the millions living throughout U.S. and Mexican GOM coastal cities and towns, can now take comfort in knowing that there's "no need for concern" regarding a tropical cyclone threat this year? Well, that just triggered a flashback. Years ago, I remember having an investment broker who used to say with conviction, "trust me, i'm positive". Hmmmm, I sort of miss her (as well as my money). Ahhh, Good times! - LOL.

I have always been leery about long range forecasts primarily predicated on persistence. While I do truly acknowledge that persistence often tends to play a role in climate conditions and forecasting, I'd say that it's naive to believe that even temporary breakdowns in the long-wave pattern just won's occur. One of the first things I ever learned about the weather was, dynamics change.

[ninel conde]

"....Was just checking the SST...GOM is the hot spot. 90F off Key West, 86-87F most rest of GOM. Need to keep storms out of the gulf......MGC

no need for concern. as in the last few years the huge heat ridge has appeared over Texas once again. GOM should be quite safe. Back in May it seemed like this year MIGHT allow some GOM development, but that has changed back to the semi-permanent east coast trof.

Really? So the millions living throughout U.S. and Mexican GOM coastal cities and towns, can now take comfort in knowing that there's "no need for concern" regarding a tropical cyclone threat this year? Well, that just triggered a flashback. Years ago, I remember having an investment broker who used to say with conviction, "trust me, i'm positive". Hmmmm, I sort of miss her (as well as my money). Ahhh, Good times! - LOL.

I have always been leery about long range forecasts primarily predicated on persistence. While I do truly acknowledge that persistence often tends to play a role in climate conditions and forecasting, I'd say that it's naive to believe that even temporary breakdowns in the long-wave pattern just won's occur. One of the first things I ever learned about the weather was, dynamics change.

For the long range of aug-oct, yes. JB is now talking about texas drying up. ridge over texas, east coast trof, wnw flow quite frankly means the coast from maine to texas is safe. one aside, if as many are now saying the east coast trof gives us yet another bitter cold east coast winter, then that will mean west coast ridge and no cali drought relief. Dynamics havent changed for a long time. just ask those in the carib waiting for years for water molecules to be present in the tropics.

[CYCLONE MIKE]

"....Was just checking the SST...GOM is the hot spot. 90F off Key West, 86-87F most rest of GOM. Need to keep storms out of the gulf......MGC

no need for concern. as in the last few years the huge heat ridge has appeared over Texas once again. GOM should be quite safe. Back in May it seemed like this year MIGHT allow some GOM development, but that has changed back to the semi-permanent east coast trof.

Really? So the millions living throughout U.S. and Mexican GOM coastal cities and towns, can now take comfort in knowing that there's "no need for concern" regarding a tropical cyclone threat this year? Well, that just triggered a flashback. Years ago, I remember having an investment broker who used to say with conviction, "trust me, i'm positive". Hmmmm, I sort of miss her (as well as my money). Ahhh, Good times! - LOL.

I have always been leery about long range forecasts primarily predicated on persistence. While I do truly acknowledge that persistence often tends to play a role in climate conditions and forecasting, I'd say that it's naive to believe that even temporary breakdowns in the long-wave pattern just won's occur. One of the first things I ever learned about the weather was, dynamics change.

Not to derail this thread, even though it was dead before it started, but I live along the gom coast and am not concerned one bit. But ninel is right. This Texas ridge is in control but it will relax but in return then there will be the east coast trough building in and vice versa. There hasnt even been any signs of tropical waves moving through this summer. By the time we get into september el nino will be in charge and as strong as that's looking gulf will be shut down for good. Patiently waiting for our early winter.

[tolakram]

Let's try and keep comments about conditions ant NOT about others opinions. I too get tired of the over confidence of some of these predictions, but they are opinions.

[hurricanehunter69]

There are never any absolutes when it comes to weather. We deal with probabilities and percentages. I'd say the odds favor the safe camp by about 70%.