2020 Indicators: SST's / SAL / MSLP / Steering / Shear / Instability / Sat Images

[FireRat]

There are good discussions about the Bermuda High and here is one more nugget to add.

https://twitter.com/webberweather/status/1275094367296983045

I'm really getting chills seeing how these indicators keep pointing to a possible 'perfect storm' situation with hyperactivity and the westward tracks. Even the SAL is weird as heck this year, as if foreshadowing something as odd and contradictory as it sounds, but being June, I wouldn't expect SAL like this during September and plus the current SAL likely was kicked up by the strong tropical waves for this time of year. I have a gut feeling South FL will seriously test its luck this year, get ready folks!! Hurricanes Irma, and Dorian might have been warning shots to this 2020.
Hurricane Michael also could be a warning shot for FL as a whole, striking one of the lesser populated parts of the state as a C5 in 2018. The big cities of Florida have been incredibly fortunate these last few decades. Hopefully the luck continues in this crazy year, would be the worst one to have the luck run out on.

Go grab the nearest slab of plywood and give it a good knock for good luck!

[USTropics]

OOF!

Yep...Let’s put this recurve discussion to bed now! This has been my concern to this point. Get ready folks

They're also mentioning that the high pressure pattern is a little further north than previous years.. anyone get that? and if so, let's discuss what that could mean.

Before we can discuss its location, let's first talk about what causes this high pressure area. Building off my previous post (viewtopic.php?p=2807655#p2807655), we can see the natural currents of the Atlantic ocean transport warm water north, where it mixes with much colder water before remaining heat is released. When we have this colder water, it lowers sea-level and surface pressures. This causes compensating high pressure areas to form (generally to the north or to the south). Introducing...the Bermuda High. So what does a typical July pattern look like? Below is an example:




Now let's talk about the source of this ocean temperature difference. Fresh water deposits from Greenland runoff, glacial melt, and other sources of fresh water all play a major factor in this. Fresh water reduces the salinity in the ocean, which results in cold water having a higher buoyancy (i.e. it doesn't sink as quickly as the rate of warmer water). So let's do a quick recap. These aren't static features of course, but below is an overlay of current sea surface temperatures and some example features:



So now that we know a higher concentration of fresh water decreases SSTs and decreases SLP, and we know this correlates to compensating high pressure areas, how can we analyze this? One way is to use NSIDC data to analyze surface melt (http://nsidc.org/greenland-today/greenl ... sis-tools/). Looking at 2020, there has been a recent spike in fresh water runoff:



While the atmosphere doesn't instantaneously respond to oceanic changes (these process are more gradual), we should start seeing a compensating high pressure area, which we are:


Now comparing this to my first image above, we can see this is currently displaced to the NW, in part due to the large baroclinic feature over NW Africa/Spain that has persisted for quite some time (which has accelerated the near historic SAL outbreak). If the CFS forecast is correct, we should be in a more traditional July setup by mid-July (although a bit zonal).



So we can also use this to explore how this impacts Atlantic hurricane tracks. An increase in fresh water will result in more ridging/a stronger area of high pressure. This increases the chance of U.S. strikes. Looking at recent active seasons with multiple U.S. strikes and their corresponding 500mb heights anomalies for those spikes:

2018



2005



2004



Some will probably remember the talk of the blocking Greenland high that causes Sandy's track, and this also coincided with historic surface melts in 2012 from July-September of that year:



While these certainly aren't the only influencing features and processes, it's one aspect that will influence steering currents as we head towards the heart of the hurricane season.

[NDG]

I know this is very early but I think the record breaking Saharan dust which seems to be never ending all the way to the Sahara will put the brakes on the thinking that this will continue to be an early active season. I can't remember such a dusty sky in very active seasons. It has put the whole MDR and Caribbean under a very hostile environment, it might even cool down some the surface waters. It will be a very long boring July for the MDR if the dust episodes continue so strong.

[AutoPenalti]

I know this is very early but I think the record breaking Saharan dust which seems to be never ending all the way to the Sahara will put the brakes on the thinking that this will continue to be an early active season. I can't remember such a dusty sky in very active seasons. It has put the whole MDR and Caribbean under a very hostile environment, it might even cool down some the surface waters. It will be a very long boring July for the MDR if the dust episodes continue so strong.

https://i.imgur.com/6PGpho0.png
https://i.imgur.com/OY4vTdz.png
https://i.imgur.com/twjwmX0.png
https://i.imgur.com/nXEdJZj.png

An active WAM will ensure this continues until the ITCZ moves north.

[toad strangler]

I know this is very early but I think the record breaking Saharan dust which seems to be never ending all the way to the Sahara will put the brakes on the thinking that this will continue to be an early active season. I can't remember such a dusty sky in very active seasons. It has put the whole MDR and Caribbean under a very hostile environment, it might even cool down some the surface waters. It will be a very long boring July for the MDR if the dust episodes continue so strong.

This graph can be posted a thousand times and it still won't be enough. Look at historical activity right up to August 1st. The main reason for this low activity is SAL. "Tis the season.

[TheStormExpert]

There are good discussions about the Bermuda High and here is one more nugget to add.

https://twitter.com/webberweather/status/1275094367296983045

I'm really getting chills seeing how these indicators keep pointing to a possible 'perfect storm' situation with hyperactivity and the westward tracks. Even the SAL is weird as heck this year, as if foreshadowing something as odd and contradictory as it sounds, but being June, I wouldn't expect SAL like this during September and plus the current SAL likely was kicked up by the strong tropical waves for this time of year. I have a gut feeling South FL will seriously test its luck this year, get ready folks!! Hurricanes Irma, and Dorian might have been warning shots to this 2020.
Hurricane Michael also could be a warning shot for FL as a whole, striking one of the lesser populated parts of the state as a C5 in 2018. The big cities of Florida have been incredibly fortunate these last few decades. Hopefully the luck continues in this crazy year, would be the worst one to have the luck run out on.

Go grab the nearest slab of plywood and give it a good knock for good luck!

Yeah I have a funny feeling Florida’s luck will be tested again this year! After all it’s 2020 and has already been a historic year, hopefully we luck out like in years past.

[USTropics]

I know this is very early but I think the record breaking Saharan dust which seems to be never ending all the way to the Sahara will put the brakes on the thinking that this will continue to be an early active season. I can't remember such a dusty sky in very active seasons. It has put the whole MDR and Caribbean under a very hostile environment, it might even cool down some the surface waters. It will be a very long boring July for the MDR if the dust episodes continue so strong.

https://i.imgur.com/6PGpho0.png
https://i.imgur.com/OY4vTdz.png
https://i.imgur.com/twjwmX0.png
https://i.imgur.com/nXEdJZj.png

An active WAM will ensure this continues until the ITCZ moves north.

There's been a noticeable shift north in the past 10 days for both branches. It's now near climatological norm for June.:

[ScottNAtlanta]

Something else to consider is that this SAL outbreak is rather far to the north for this time of year. I think that's why you are seeing a lot more impacts in the islands rather than a good portion going into South America.

[toad strangler]

 http://twitter.com/BigJoeBastardi/status/1275431930671104001

[cycloneye]

More Noll nuggets.

 https://twitter.com/BenNollWeather/status/1275447269052080128

[SFLcane]

More Noll nuggets.

https://twitter.com/BenNollWeather/status/1275447269052080128

Going to be a wild year!!

[MarioProtVI]

Something I noticed: The previous two seasons which had 4 named storms before June 30 ended up having a dead July. I think it’s possible despite the signals July could be unfavorable especially given the recent SAL outbreak which was one the strongest on record. In addition, if the Atlantic keeps producing minimalistic storms like Dolly there is a possible chance of a hurricane minority, which means 2020 would have to have like 5-7 hurricanes in a row by early-mid September which although quite possible with the setup is something only the most of hyperactive seasons have achieved, re: 2005, 2010, 2017. This is just my thinking though.

[toad strangler]

I like Joe but he sure does have every base covered doesn't he?

 http://twitter.com/BigJoeBastardi/status/1275463569119813634

[Shell Mound]

More Noll nuggets.

https://twitter.com/BenNollWeather/status/1275447269052080128

Actually, isn’t Africa rather than the IO typically dominant during the most active Atlantic seasons? I did a composite of VP anomalies for hyperactive seasons since 1995—1995, 1996, 1998, 1999, 2004, 2005, 2010, and 2017—and found that the -VP standing wave was centred over West-Central Africa rather than the western IO, with a secondary -VP anomaly over or very near the MC and negative anomalies centred on the International Date Line. The ECMWF forecast for September 2020 centres the sinking branch farther W and the standing wave farther E than is typical during (the mean of) hyperactive seasons, including 2005 and 2017. Along with the CFSv2, the ECMWF suggests that sinking air could become a problem for the Atlantic during the peak of the season, so if July turns out to be inactive, then the shift toward a sinking branch over most of the MDR could, depending on the state of the MJO, offset the active WAM/AEJ and partly “shut down” the season.

USTropics, do you care to chime in on this and possibly correct me if necessary?

[JPmia]

I recall heavy SAL outbreaks in 2005 as well. Don't know where those old maps are, but that's what I recall.

[TheStormExpert]

I like Joe but he sure does have every base covered doesn't he?

http://twitter.com/BigJoeBastardi/status/1275463569119813634?s=20

Those tweets yesterday about the ridge bridge may back this up.

[StruThiO]

 https://twitter.com/webberweather/status/1275513104449916930

[CyclonicFury]

It's important to note that while the first four named storms have been weak, that is not necessarily a predictor of the overall intensity of the season. 2017 is a prime example of this - 5 named storms and no hurricanes before August 1, and less than 3 ACE. 2017 then went on to produce 220+ ACE and 10 consecutive hurricanes, 6 of which became majors.

[Shell Mound]

It's important to note that while the first four named storms have been weak, that is not necessarily a predictor of the overall intensity of the season. 2017 is a prime example of this - 5 named storms and no hurricanes before August 1, and less than 3 ACE. 2017 then went on to produce 220+ ACE and 10 consecutive hurricanes, 6 of which became majors.

How do you think the IO signal may affect the level of activity in the Atlantic basin?

[CyclonicFury]

It's important to note that while the first four named storms have been weak, that is not necessarily a predictor of the overall intensity of the season. 2017 is a prime example of this - 5 named storms and no hurricanes before August 1, and less than 3 ACE. 2017 then went on to produce 220+ ACE and 10 consecutive hurricanes, 6 of which became majors.

How do you think the IO signal may affect the level of activity in the Atlantic basin?

I'm not convinced it will have a major effect, most models are predicting the IOD to be about neutral during the peak of the season at the moment. I've heard conflicting ideas about how the IOD affects Atlantic activity. While a +IOD would favor upward motion over Africa, it is often concurrent with an El Nino and tends to lead to increased Atlantic shear. A -IOD concentrates the rising motion farther east, and typically occurs during La Nina events.