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

[CyclonicFury]

It's interesting to note that all of the last 5 Atlantic tropical cyclones (Gonzalo, Hanna, Isaias, TD 10 and now TD 11) have all formed from tropical waves. One interesting little-known fact about 2005 was the first 15 TCs all formed from tropical waves.

[SootyTern]

It's the same exact people posting the same exact stuff that they posted on the 2017 indicators thread at this date. The only thing that seems 'off' to me this year is the unanimously aggressive forecasts by the different entities contrasted with how mellow the GFS is these days. It is Aug 11 and the GFS has yet to run a sub-940 monster over my house in the medium to long range. I kinda miss its wacky hijinks!

[Hammy]

It's interesting to note that all of the last 5 Atlantic tropical cyclones (Gonzalo, Hanna, Isaias, TD 10 and now TD 11) have all formed from tropical waves. One interesting little-known fact about 2005 was the first 15 TCs all formed from tropical waves.

15 years later and I only just now find out Nate had tropical origin (just double checked, moved off Africa Aug 30)--one of those small things but I'd always thought it was the same trough as Ophelia formed from.

[aspen]

I think we should be keeping an eye out for an AEW trying to get into the Gulf within the next 10-15 days. Not only have some of the model ensembles hinted at a storm in the Gulf later this month, but SSTs are so absurdly high — 30-31 C from Corpus Christi all the way to the Florida Keys — that we could see a storm bomb out right through landfall like Harvey or Michael. Those coastal waters are hot enough to support a powerful Cat 5, and the rest of the Gulf is not far behind (mainly 29-30 C). If anything gets in there and happens to find an area with a conductive environment, it is going to explode.

[captainbarbossa19]

I think we should be keeping an eye out for an AEW trying to get into the Gulf within the next 10-15 days. Not only have some of the model ensembles hinted at a storm in the Gulf later this month, but SSTs are so absurdly high — 30-31 C from Corpus Christi all the way to the Florida Keys — that we could see a storm bomb out right through landfall like Harvey or Michael. Those coastal waters are hot enough to support a powerful Cat 5, and the rest of the Gulf is not far behind (mainly 29-30 C). If anything gets in there and happens to find an area with a conductive environment, it is going to explode.

Another member on the Texas Summer forum mentioned recently that the Euro weeklies showed a potential weakness towards late August that could pull storms into the Gulf.

[USTropics]

Going back to 1948, here are seasons that had 4 or more named storms active during the second part of August and what those VP anomalies looked like (peak intensity in parentheses).

2012 - Helen (TS), Gordon (C2), Isaac (C1), Joyce (TS), Kirk (C2), Lesli (C1)


2011 - Franklin (TS), Gert (TS), Harvey (TS), Irene (C3), Jose (TS), Katia (C4)


2010 - Collin (TS), Danielle (C4), Earl (C4), Fiora (TS)


2009 - Ana (TS), Bill (C4), Claudette (TS), Danny (TS)


2005 - Irene (C2), Jose (TS), Katrina (C5), Lee (TS)


2004 - Charley (C4), Danielle (C2), Earl (TS), Frances (C4), Gaston (C1), Hermine (TS)


1999 - Bret (C4), Cindy (C4), Dennis (C2), Emily (TS)


1998 - Bonnie (C3) Charley (TS), Danielle (C2), Earl (C2)


1996 - Dolly (C1), Edouard (C4), Fran (C3), Gustav (TS)


1995 - Felix (C4), Gabrielle (TS), Humberto (C2), Iris (C2), Jerry (TS), Karen (TS), Luis (C4)


1993 - Bret (TS), Cindy (TS), Emily (C3), Dennis (TS)


1976 - Belle (C3), Dottie (TS), Candice (C1), Emmy (C2), Frances (C3)


1969 - Blanche (C1), Camille (C5), Debbie (C3), Eve (TS), Francelia (C3)


1958 - Becky (TS), Cleo (C4), Daisy (C4), Ella (C2)


1955 - Connie (C4), Diane (C2), Edith (C2), Five (TS)


1950 - Able (C3), Baker (C2), Charlie (C2), Dog (C4)


This should give more context to the VP forecast from the latest CFS run:

[captainbarbossa19]

Going back to 1948, here are seasons that had 4 or more named storms active during the second part of August and what those VP anomalies looked like (peak intensity in parentheses).

2012 - Helen (TS), Gordon (C2), Isaac (C1), Joyce (TS), Kirk (C2), Lesli (C1)
https://i.imgur.com/wV86M9F.png

2011 - Franklin (TS), Gert (TS), Harvey (TS), Irene (C3), Jose (TS), Katia (C4)
https://i.imgur.com/cdnedDT.png

2010 - Collin (TS), Danielle (C4), Earl (C4), Fiora (TS)
https://i.imgur.com/DNm2tyO.png

2009 - Ana (TS), Bill (C4), Claudette (TS), Danny (TS)
https://i.imgur.com/3bwekfg.png

2005 - Irene (C2), Jose (TS), Katrina (C5), Lee (TS)
https://i.imgur.com/2n4Rg4f.png

2004 - Charley (C4), Danielle (C2), Earl (TS), Frances (C4), Gaston (C1), Hermine (TS)
https://i.imgur.com/XNv9Xu6.png

1999 - Bret (C4), Cindy (C4), Dennis (C2), Emily (TS)
https://i.imgur.com/Fzgv2fs.png

1998 - Bonnie (C3) Charley (TS), Danielle (C2), Earl (C2)
https://i.imgur.com/cF6z748.png

1996 - Dolly (C1), Edouard (C4), Fran (C3), Gustav (TS)
https://i.imgur.com/BnkRv02.png

1995 - Felix (C4), Gabrielle (TS), Humberto (C2), Iris (C2), Jerry (TS), Karen (TS), Luis (C4)
https://i.imgur.com/RoVVyzF.png

1993 - Bret (TS), Cindy (TS), Emily (C3), Dennis (TS)
https://i.imgur.com/VE8Adrs.png

1976 - Belle (C3), Dottie (TS), Candice (C1), Emmy (C2), Frances (C3)
https://i.imgur.com/im4PLJo.png

1969 - Blanche (C1), Camille (C5), Debbie (C3), Eve (TS), Francelia (C3)
https://i.imgur.com/tCr7PAI.png

1958 - Becky (TS), Cleo (C4), Daisy (C4), Ella (C2)
https://i.imgur.com/wcGG8Vn.png

1955 - Connie (C4), Diane (C2), Edith (C2), Five (TS)
https://i.imgur.com/QPjJ98i.png

1950 - Able (C3), Baker (C2), Charlie (C2), Dog (C4)
https://i.imgur.com/hsNtcid.png

This should give more context to the VP forecast from the latest CFS run:
https://i.ibb.co/bgRYrcN/cfs-avg-chi200-Mean-global-fh168-840.gif

Looking at all of these maps, it appears that there really isn't a strong correlation between VP anomalies and basin activity. For example, 2005 had plenty of rising air over Africa, but the western basin had quite a bit of sinking air. I wonder if the sinking air was still being recorded when Katrina was in the Gulf? The anomaly looks like formation would be unfavorable. On the other hand, 1998 featured lots of rising motion over most of the Atlantic, but the number of storms is equivalent to the number of storms in 2005.

[Hammy]

Looking at all of these maps, it appears that there really isn't a strong correlation between VP anomalies and basin activity. For example, 2005 had plenty of rising air over Africa, but the western basin had quite a bit of sinking air. I wonder if the sinking air was still being recorded when Katrina was in the Gulf? The anomaly looks like formation would be unfavorable. On the other hand, 1998 featured lots of rising motion over most of the Atlantic, but the number of storms is equivalent to the number of storms in 2005.

2005 actually had a limited number of storms develop in the latter half of August--Katrina of course, and two very short-lived tropical storms. Irene formed on August 4 and was simply continuing along and headed out to sea by mid-August.

1998 on the other hand featured a significant burst of activity at the end of August--four storms being named over the last 11 days--two in the Gulf, and two fairly long-trackers (Bonnie and Danielle)

[USTropics]

Looking at all of these maps, it appears that there really isn't a strong correlation between VP anomalies and basin activity. For example, 2005 had plenty of rising air over Africa, but the western basin had quite a bit of sinking air. I wonder if the sinking air was still being recorded when Katrina was in the Gulf? The anomaly looks like formation would be unfavorable. On the other hand, 1998 featured lots of rising motion over most of the Atlantic, but the number of storms is equivalent to the number of storms in 2005.

2005 actually had a limited number of storms develop in the latter half of August--Katrina of course, and two very short-lived tropical storms. Irene formed on August 4 and was simply continuing along and headed out to sea by mid-August.

1998 on the other hand featured a significant burst of activity at the end of August--four storms being named over the last 11 days--two in the Gulf, and two fairly long-trackers (Bonnie and Danielle)

That's correct. The latter half of August in 2005, while still having 4 active storms, was a bit of a break from the hyperactivity. Here is a week by week animation of 2005 and 1998 (you'll notice positive VP anomalies move into the IO/eastern Africa by last week of August 2005, which resulted in a flurry of activity first 3 weeks of September in 2005).

2005


1998


Also the strongest correlation of activity is when positive VP anomalies are centered over eastern Africa/IO. You'll see in the composite image below for all years (2012,2011,2010,2009,2005,2004,1999,1998,1996,1995,1993,1976,1969,1958,1955,1950) that sinking air is seen commonly in the western Atlantic in active August seasons:

[USTropics]

The ITCZ has really booked it north the past 10 days, now anomalously located to the north:






This will act as a primer to future waves, as well as put a damper on regions that produce heavy SAL.

[TheStormExpert]

Looking at all of these maps, it appears that there really isn't a strong correlation between VP anomalies and basin activity. For example, 2005 had plenty of rising air over Africa, but the western basin had quite a bit of sinking air. I wonder if the sinking air was still being recorded when Katrina was in the Gulf? The anomaly looks like formation would be unfavorable. On the other hand, 1998 featured lots of rising motion over most of the Atlantic, but the number of storms is equivalent to the number of storms in 2005.

2005 actually had a limited number of storms develop in the latter half of August--Katrina of course, and two very short-lived tropical storms. Irene formed on August 4 and was simply continuing along and headed out to sea by mid-August.

1998 on the other hand featured a significant burst of activity at the end of August--four storms being named over the last 11 days--two in the Gulf, and two fairly long-trackers (Bonnie and Danielle)

2005 also had only two hurricanes form during the month of August. Irene earlier on which was only a Cat.2 and of course Katrina which was a monster Cat.5. September saw five hurricanes that year with still only two being majors.

Really 2005 didn’t feature any insane in intensity long-trackers besides Dennis and Emily which was in July. Yes ACE was at record levels but it was the amount of storms, hurricanes, and majors that made up the year, not to mention as everyone says it was a west-based/loaded season with only two hurricanes in the Tropical Atlantic both being only Cat.1’s.

[Steve]

Hey USTropics,

I have a couple questions for you or anyone else who knows based on those prior year maps. First is what is your opinion of lag/incubation time between passage of those upward motion features and US threat? It seems to me that many of the more extreme storms were at/near the US in the suppressed phases. Tell me if I'm wrong or misreading this point. The maps seem to indicate that upward motion events pass through west to east and moisten up the environment and possibly spur genesis. But then the threats seem to come when those upward motion phases are far to our east. If that assumption is correct, would you agree there would generally be a several days to 2 week lag from passage to corresponding threat?

[TheHurricaneGod]

Things are about to go boom in the Atlantic. The bulk of the activity will likely be the end of August into late September like it was during most previous hyperactive seasons. Hyperactive season remains on track

[USTropics]

Hey USTropics,

I have a couple questions for you or anyone else who knows based on those prior year maps. First is what is your opinion of lag/incubation time between passage of those upward motion features and US threat? It seems to me that many of the more extreme storms were at/near the US in the suppressed phases. Tell me if I'm wrong or misreading this point. The maps seem to indicate that upward motion events pass through west to east and moisten up the environment and possibly spur genesis. But then the threats seem to come when those upward motion phases are far to our east. If that assumption is correct, would you agree there would generally be a several days to 2 week lag from passage to corresponding threat?

Your assessment is dead on. There is a bit of lag time from the period when the rising air (enhanced phase) crosses over a region (typically 2-5 days depending on other parameters noted below). This is definitely tied in intricately to your MJO posts and propagation to phases, and typically has a west to east movement like you described (an enhanced phase followed by a suppressed phase and vice versa). There are variances though, and this likely has some connection to MJO and getting "stuck" in phases (such as a standing wave positioned over the IO).

The reason we see the highest potential for activity when the enhanced phase is centered over Africa/IO is two fold. For starters, like you described, as the enhanced phase passes conditions become more conducive for tropical formation in the Atlantic (RH values increase, shear decreases, and rising motion is enhanced). In addition, the seeding process and early formative stages of these AEWs is enhanced. As described above, we see suppressed phases followed by active phases, so we are likely seeing sinking air in the western Atlantic because of this global propagation. The difference of course is, a well developed system that reaches the suppressed area after passing over the enhanced area is much more equipped to handle those conditions and create a local environment that protects against the background state.

[Steve]

Awesome. Thanks for the reply and confirmation on that.

[1900hurricane]

Instead of looking at named storms, why not look at ACE instead? It's possible VPA will have a stronger correlation with that. Here's how seasons beginning in 1950 ranked in terms of ACE for the August 15-31st time period. The top ten seasons are highlighted in yellow.

[cycloneye]

Not so fast but eventually the Atlantic will turn active.

 https://twitter.com/ToddKimberlain/status/1293632339784892418

[Kingarabian]

Not so fast but eventually the Atlantic will turn active.

[url]https://twitter.com/ToddKimberlain/status/1293632339784892418[url]

These are good points. But the fact of the matter is that these aren't like the big bad 2014-2018 EPAC systems. Most of these modeled systems are either much smaller in size so limited outflow and much weaker than forecast. Also a lot of these systems have had to move further west in order to develop. The global models EPAC TC exaggeration is on another level this year.

[Monsoonjr99]

One thing that is "off" is that there have already been 5 TC landfalls in the United States, including two hurricanes.

I can't imagine what we're in for after August 20...

[aspen]

Not so fast but eventually the Atlantic will turn active.

[url]https://twitter.com/ToddKimberlain/status/1293632339784892418[url]

These are good points. But the fact of the matter is that these aren't like the big bad 2014-2018 EPAC systems. Most of these modeled systems are either much smaller in size so limited outflow and much weaker than forecast. Also a lot of these systems have had to move further west in order to develop. The global models EPAC TC exaggeration is on another level this year.

How well the shear forecast verifies also depends on how close to 0/70 system gets to the Mexican coast. If it gets really close, it will have limited development and might not even break Cat 1 status. If it’s further away, it’ll have less land interaction and more time to bomb out into a major. The stronger it gets, the more shear will be in the Atlantic until this burst of EPac activity ends.