2017 indicators: SST's / MSLP / SAL / Steering / Instability

[gatorcane]

Might be an indicator of a more active Atlantic season than we have seen in awhile in that the GFS is showing higher shear anomalies over the East EPAC in the medium to long-range with below normal shear across the Caribbean. It could be ephemeral but this time of year we would expect lower shear across across the Eastern EPAC.

[TheAustinMan]

RAMMB/SSD's instability archives haven't been updating past 2013, so I browsed around for instability charts people happened to save on forums, blogs, and etc. and found enough early season material to stitch together a graph of 2013, 2014, 2015, 2016, and 2017's tropical Atlantic instability. Unfortunately the other graphs aren't posted as often so I probably can't stitch together a similar quantity of data for other regions or tropical cyclone formation potential variables like wind shear or cold water vapor areal coverage.

[cycloneye]

Positive AMO is favorable for Atlantic.

 https://twitter.com/philklotzbach/status/870809428647215105



 https://twitter.com/philklotzbach/status/870810792102252545



 https://twitter.com/EricBlake12/status/870812963195801601

[gatorcane]

Tropical Tidbits own Levi Cowan and his 2017 Atlantic Hurricane Season Outlook.

http://www.tropicaltidbits.com/blog/2017/06/02/outlook-for-the-2017-atlantic-hurricane-season/

https://youtu.be/H3FxehVzRAc

Good video as always from Levi. One thing I disagree with him on is the warmer SST anomalies in the subtropical Western Atlantic off the United States potentially disrupting upward motion and hurricane activity across the MDR. He points out 2013 but the inactivity that year was due to above normal amounts of dry mid-level air across the Atlantic more than anything else. Also just take a look at the warmer subtropical anomalies in 2004 during the peak of that highly active MDR season which had no negative impact and compare to what we have now. If we go by SST anomalies, this screams active MDR season assuming no major SST anomaly config changes between now and the peak:

[TheStormExpert]

Tropical Tidbits own Levi Cowan and his 2017 Atlantic Hurricane Season Outlook.

http://www.tropicaltidbits.com/blog/2017/06/02/outlook-for-the-2017-atlantic-hurricane-season/

https://youtu.be/H3FxehVzRAc

Good video as always from Levi. One thing I disagree with him on is the warmer SST anomalies in the subtropical Western Atlantic off the United States potentially disrupting upward motion and hurricane activity across the MDR. He points out 2013 but the inactivity that year was due to above normal amounts of dry mid-level air across the Atlantic more than anything else. Also just take a look at the warmer subtropical anomalies in 2004 during the peak of that highly active MDR season which had no negative impact and compare to what we have now. If we go by SST anomalies, this screams active MDR season assuming no major SST anomaly config changes between now and the peak:

The one big difference I'm seeing is the colder patch of SST's in the mid-latitudes which could help keep the Bermuda High weak to nonexistent.

OFF TOPIC: Look at how you can see the cool patches of SST's just north and east of the Eastern Caribbean in the 2004 map due to Hurricane Frances going over that area.

[chaser1]

Tropical Tidbits own Levi Cowan and his 2017 Atlantic Hurricane Season Outlook.

http://www.tropicaltidbits.com/blog/2017/06/02/outlook-for-the-2017-atlantic-hurricane-season/

https://youtu.be/H3FxehVzRAc

Good video as always from Levi. One thing I disagree with him on is the warmer SST anomalies in the subtropical Western Atlantic off the United States potentially disrupting upward motion and hurricane activity across the MDR. He points out 2013 but the inactivity that year was due to above normal amounts of dry mid-level air across the Atlantic more than anything else. Also just take a look at the warmer subtropical anomalies in 2004 during the peak of that highly active MDR season which had no negative impact and compare to what we have now. If we go by SST anomalies, this screams active MDR season assuming no major SST anomaly config changes between now and the peak:

The one big difference I'm seeing is the colder patch of SST's in the mid-latitudes which could help keep the Bermuda High weak to nonexistent.

That's an interesting point to debate. Assuming that Atlantic SST anomalies go largely unchanged, the result would clearly seem to indicate the majority of developing East & Central Atlantic T.S. and hurricanes would generally recurve well east of the Conus. If that verified the result would seem to diminish the U.S. East coast and Canadian Maritimes threat somewhat, and perhaps even more profoundly lessen the risk to a large portion of the Caribbean basin.

IMO though, I'm not seeing those cold N. Atlantic anomalies to "cause" a weaker Bermuda high especially to the extent where it alone would establish the overall longeave pattern. Possibly a contributing factor to a temporary erosion of a already marginal mid level heights if that were the case. I'm more apt to think that present cold N. Atlantic SST anomolies are more the "result of" the past and recent circulation and as such, a result of the past and recent long wave pattern.

Its hard for me to quite guess how strong the N. Atlantic ridging will be this year or for that matter how far west and south it will be oriented. I do think however, that we might see anomalous strong ridging across a large portion of the sub-tropics and reaching westward to at least 70W-80W, along with overall ridging over portions of the S.E. Conus and often extending south & east to Florida. Two results of what i'm guessing will occur will be the gradual warming of N. Atlantic SST's that will approach near normal by late Summer, and deep troughing off the Northerm & Western Africa coast. If the very warm SST's continue to persist (or even expand) in the far East Atlantic and just off the Aftican coast, we may once again see some pretty well developed lows emerge off the coast and immediately begin to organize and quickly pulled more homeward. At least that's what I'd suspect assuming some abrupt weakness in the Easterlies (and at what latitude the ITCZ or any monsoonal low will be at.

[AutoPenalti]

Atlantic instability looks like it's about to level off again and go below normal.

Which means?

[Kazmit]

Atlantic instability looks like it's about to level off again and go below normal.

Which means?

Generally,
More instability = more activity
Less instability = less activity

[tolakram]

Instability also tends to be a lagging indicator. More storms, more instability.

If you didn't know anything about the Gulf in 2005 except this chart, was this a big season?


Tropical Atlantic instability in 2006. Big season?

[TheStormExpert]

 https://twitter.com/mjventrice/status/870969546349445121

[AutoPenalti]

Wind Shear maps aren't available right now but it doesn't really take that to know that it is unfavorable right now at mid-level and upper-level for any sort of TC genesis.

[ScottNAtlanta]

I was under the impression that the cooler water would increase the likelihood of a stronger high pressure while increasing the lower pressure in the MDR. Warm Oceans imply warmed or rising air when you have a cooler source region adjacent which would imply cooler or sinking air. The last several seasons there really wasnt much contrast thus you had high pressure throughout. I would infer from this a stronger High in the subtropical regions where the water is anomalously cooler. Also the cooler than normal water off the Mexican coast will also have more sinking air this year than the last couple of years.

[weathaguyry]

Not too bad for this time of year!

http://tropic.ssec.wisc.edu/real-time/m ... t72hrs.gif

[cycloneye]

Very warm anomalies in West Atlantic that may rob some energy from MDR according to what Levi discussed in his recent video.

[Ntxw]

I was under the impression that the cooler water would increase the likelihood of a stronger high pressure while increasing the lower pressure in the MDR. Warm Oceans imply warmed or rising air when you have a cooler source region adjacent which would imply cooler or sinking air. The last several seasons there really wasnt much contrast thus you had high pressure throughout. I would infer from this a stronger High in the subtropical regions where the water is anomalously cooler. Also the cooler than normal water off the Mexican coast will also have more sinking air this year than the last couple of years.

I don't know about the tropics but in the subtropics and extratropics cooler waters mean lower than normal pressures. This is due to the storms (lower pressures) up-welling the water from beneath. High pressures is sinking air that prevents systems thus no up-welling meanwhile sunshine warms up the water unabated. This is why parts of the gulf have cooled dramatically, persistent convection and rains.

In the tropics itself, it may be a different story as trade winds play a different role and warm water is able to readily sustain convection.

[NDG]

Usually when cooler waters get left behind in the subtropical Atlantic after weeks of a stormy pattern and upwelling that's when high pressure finds a home due to subsidence and mid level ridging after a pattern change such as the NAO going positive, IMO.

[wxman57]

I'm seeing a weaker SAL this June vs. recent years. Weaker subtropical high is the reason. Possibly a sign that the MDR will be more active this year.

[MGC]

I'm seeing a weaker SAL this June vs. recent years. Weaker subtropical high is the reason. Possibly a sign that the MDR will be more active this year.

As long as the storms recurve before the islands I'd be happy with that.....MGC

[Kazmit]

Not much dry air at all. I agree with others that we might see more storms develop in the MDR and more long-tracking Cape Verde hurricanes.

[cycloneye]

 https://twitter.com/TropicalTidbits/status/872574642040569857