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

[Ubuntwo]

The MDR is NOT much cooler than average as some of these posts would make you think. It may be cooler than 2005, 2010 or 2017, but those years had near-record MDR SSTAs.

This. The anomalies at this point are negligible..... HEADING into the warmest months.

It depends on the data source used. The NOAA Coral Reef Watch maps make the MDR look fairly similar to 2017, while the CDAS/OISST show a mixed MDR that is mostly warmer than normal in the southeast and cooler than normal in the northwest. However I think the Coral Reef Watch maps have a warm bias in the MDR.

I think it's the climo period used, not a bias.

[TheStormExpert]

Currently the Atlantic MDR is just ever so slightly above normal but staying steady.





Btw, does anyone know what happened to the Atlantic SST anomalies archive page? I can't find it.

[TheAustinMan]

Well, it's not so much about supporting a storm as the fact that if the MDR waters stay cooler than usual while the waters to the north stay warmer than usual, that promotes sinking and stability. Which prevents storms from even forming.

https://i.imgur.com/QDjLaif.png

Wow uh... I would not pay attention to that black line, which supposedly represents climatology. A few years ago, RAMMB/CIRA changed their statistical methodology for that product, using a larger 500 km averaging radius that would incorporate more of the mid-latitude regions and thus have lower instability values. The black line doesn't take that to account, so pretty much every year we've seen that plot show below-average values year-round when that isn't necessarily case. The archives on the other hand correct for this, but unfortunately that archive only goes from 2000-2017 so there's no corrected version for 2020. You'll notice that the values of the average line on say 2017 for instance are completely different.

It wouldn't be surprising if MDR instability was a bit below average right now, given the SST configuration, but it's probably not missing the mark by that much.

Anyhow, the MDR could warm further, which would not be a big surprise given that easterlies are suppressed across much for the MDR, perhaps all the way through the end of May.

55KB. SST trend over the last 7 days. Source: NOAA Coral Reef Watch 5km Products


1 MB. Hovmoller plot of GFS zonal wind anomalies at 1000hPa. The Atlantic MDR is on the right side of this graphic. Red/warm shading indicates weaker easterlies/stronger westerlies than average. Blue/cold shading indicates stronger easterlies/weaker westerlies than average. Source: Cyclonicwx.com

[CyclonicFury]

Important excerpt from the NOAA outlook:

Predicting the location, number, timing, and strength of tropical storm and hurricane landfalls are ultimately related to the daily weather patterns, storm genesis locations, and steering patterns. These patterns are not predictable weeks or months in advance. As a result, it is not possible to reliably predict the number or intensity of landfalling storms in a seasonal outlook, or whether a given locality will be impacted by a hurricane this season.

[toad strangler]

Important excerpt from the NOAA outlook:

Predicting the location, number, timing, and strength of tropical storm and hurricane landfalls are ultimately related to the daily weather patterns, storm genesis locations, and steering patterns. These patterns are not predictable weeks or months in advance. As a result, it is not possible to reliably predict the number or intensity of landfalling storms in a seasonal outlook, or whether a given locality will be impacted by a hurricane this season.

Calling ShellMound. He called large swaths of places safe due to the track of Arthur

[jconsor]

The climatology periods used by NOAA Coral Reef and CDAS are not very different. NOAA Coral Reef uses 1985-2012: https://coralreefwatch.noaa.gov/product ... tology.php

CDAS and OISST (at least the one available on cyclonicwx.com) both use 1981-2010.

This. The anomalies at this point are negligible..... HEADING into the warmest months.

It depends on the data source used. The NOAA Coral Reef Watch maps make the MDR look fairly similar to 2017, while the CDAS/OISST show a mixed MDR that is mostly warmer than normal in the southeast and cooler than normal in the northwest. However I think the Coral Reef Watch maps have a warm bias in the MDR.

I think it's the climo period used, not a bias.

[Nuno]

I’m completely dumbfounded at how married many are to even the slightest neg anomalies in the MDR as a huge inhibitor. The MDR is highly overrated I’ve come to learn.

It is the breeding ground for most tropical cyclones, I hope you realize that?

Tropical cyclones form in many places outside of the MDR, I hope you realize that?

As a Floridian, my eyes are typically peeled to how the conditions closer to home are. MDR anomalies are not the only factor.

[AutoPenalti]

The calls of reduced numbers or even an inactive season because of a slight dip in SST's in the MDR is kinda ridiculous. There's more than just warm sea surface temperatures that can define a season.

[TheAustinMan]

Here's an interesting thought — we often talk about SST configuration in the preseason as a predictor of how active the season will be. However, how well are SSTs in May correlated with seasonal activity?

Decided it'd be fun to try to find this out using the NCEP/NCAR SST reanalysis from 1948-2019 and the seasonal ACE values for those years. I took a look at a whole bunch of points in the Atlantic and Eastern Pacific, and for each point, got the mean SST in a 5x5 degree gridbox centered on that point for each year and then compared it to the total seasonal ACE, getting an r^2 value indicating the strength of a (linear) correlation for each point.

If you were to guess where Atlantic SSTs in May were most strongly correlated with ACE, what would you guess? Did you guess the eastern Atlantic between Cape Verde and the Canary Islands? It took a very long while, but here are the results. Red shades indicate a positive correlation (warmer SSTs in May correlates with more seasonal activity) and blue shades indicate a negative correlation (cooler SSTs in May correlates with less seasonal activity). The darker the shading the stronger the linear correlation.

Given how many variables are involved in determining seasonal activity, it's no surprise that the correlation between May SSTs and ACE, at least numerically, is rather weak. r^2 values were at most about 0.3, which definitely isn't strong. But perhaps the spatial distribution of where things are more strongly or weakly correlated may tell us something about where to look in May for SSTs.

There's two maps here. I don't want to be misleading with the colors, so I wanted to emphasize first that the numerical correlation is rather weak; the first map has softer shading to reflect that. The second map has darker shading to bring out the spatial details, but don't confuse the harsher colors for a strong correlation necessarily - the r^2 values are still low overall.

890KB. Source: Generated myself using QGIS and data from ESRL


908KB. Color scale enhanced here to bring out spatial details, but don't confuse the darker shading for a necessarily strong correlation. Source: Generated myself using QGIS and data from ESRL


The way I produce this data takes a rather long time, but I'll probably make additional maps for other months and other regions later.

[aspen]

I’m completely dumbfounded at how married many are to even the slightest neg anomalies in the MDR as a huge inhibitor. The MDR is highly overrated I’ve come to learn.

It is the breeding ground for most tropical cyclones, I hope you realize that?

Tropical cyclones form in many places outside of the MDR, I hope you realize that?

As a Floridian, my eyes are typically peeled to how the conditions closer to home are. MDR anomalies are not the only factor.

Well, a long-tracking MDR hurricane can mean the difference between an above-average and a hyperactive season. Take 2017 for example; if Irma never existed, it’s total ACE would “only” be 160 units and not 225. However, it still would’ve been the costliest season on record because of closer-to-home systems like Harvey and Maria (which, yes, was technically a MDR storm, but it wasn’t a classic Cape Verde system like Irma and formed much closer to the Caribbean).

[toad strangler]

The calls of reduced numbers or even an inactive season because of a slight dip in SST's in the MDR is kinda ridiculous. There's more than just warm sea surface temperatures that can define a season.

ABSOLUTELY. I don't know what it is about this place but MDR SST's are the end all for more than a few. There is WAY too much variability in play to tag that one measure with such significance. Especially when the negative measure in TINY compared to normal.

[BYG Jacob]

What on Earth has some posters here convinced SSTs won't be warm enough to generate and sustain intense storms during ASO?

[AxaltaRacing24]

What on Earth has some posters here convinced SSTs won't be warm enough to generate and sustain intense storms during ASO?

i’m confused as to why posters are acting like the MDR is reaching record lows. if i’m not mistaken, isn’t it literally above average right now?

[CyclonicFury]

While it has been widely documented that SSTs over the MDR are cooler than 2005, 2010, and 2017, I decided to take a look at some other hyperactive (153+ ACE) seasons since 1995 and see how they compare to 2020. I used a monthly average from April 20-May 19 to eliminate noise. The MDR is pretty similar to 2004, and actually warmer than 1999 and 2003 over the same time span.

Here's 2020 for reference:


1995: The MDR was mostly warmer than 2020 overall, though parts of the eastern tropical Atlantic were cooler than normal (which interestingly is warmer than normal in 2020).


1996: The eastern MDR was warmer than normal, but the western MDR and Caribbean were actually cooler than normal.


1998: The MDR was warmer than normal throughout. Solidly warmer than 2020. The MDR is typically warmer than normal the spring following significant El Ninos, due to reduced low-level winds in the MDR during winter as a result of more frequent -NAO.


1999: The MDR was generally cooler than normal, definitely cooler than 2020. However, notice that the eastern subtropical Atlantic was warmer than normal, similar to 2020. Anomalously warm SSTs in this region during May are positively correlated with activity as much as MDR SSTs. Despite the cool MDR during April/May, 1999 had five major hurricanes and an ACE of 178 units.


2003: The MDR was quite cool during April/May 2003 (definitely cooler than 2020), and the Atlantic actually somewhat resembled a -AMO pattern during this time. Although 2003 finished with a hyperactive ACE total, the ACE was generated largely as a result of two Cabo Verde type long trackers in Fabian and Isabel.


2004: This one was the most surprising. 2004 was an extremely strong season, with the season producing 6 major hurricanes and ~225 ACE. The MDR was not particularly warmer than normal in April/May 2004, it was slightly above average similar to 2020.


The truth is, just because a few spots in the MDR are cooler than normal does not necessarily mean the MDR will be dead or the season will be quiet. There are also some seasons with relatively warm MDRs that end up having limited activity in this region (such as the infamous 2013). It's far more complex than that. Just look at Florence in 2018 for an example, it reached Category 4 status over below-normal SSTs in the east-central MDR. I would expect at least 2-4 hurricanes to develop over the MDR this season.

In theory, this season has a significantly more favorable SST profile for the Atlantic than the past two (both of which finished above average in Atlantic activity by most metrics), along with a cooler ENSO.

[TheStormExpert]

What on Earth has some posters here convinced SSTs won't be warm enough to generate and sustain intense storms during ASO?

i’m confused as to why posters are acting like the MDR is reaching record lows. if i’m not mistaken, isn’t it literally above average right now?

No one is saying record cold SST’s in the Atlantic MDR! The MDR is by the way ever so slightly sustaining itself above normal overall in SST anomalies, it’s been staying steady for a week now.

[StruThiO]

While it has been widely documented that SSTs over the MDR are cooler than 2005, 2010, and 2017, I decided to take a look at some other hyperactive (153+ ACE) seasons since 1995 and see how they compare to 2020. I used a monthly average from April 20-May 19 to eliminate noise. The MDR is pretty similar to 2004, and actually warmer than 1999 and 2003 over the same time span.

Thank you for this post

[CyclonicFury]

While it has been widely documented that SSTs over the MDR are cooler than 2005, 2010, and 2017, I decided to take a look at some other hyperactive (153+ ACE) seasons since 1995 and see how they compare to 2020. I used a monthly average from April 20-May 19 to eliminate noise. The MDR is pretty similar to 2004, and actually warmer than 1999 and 2003 over the same time span.

Thank you for this post

No problem! It is always interesting to actually look at the SST anomaly data to see how seasons turned out.

[MJGarrison]

Here's an interesting thought — we often talk about SST configuration in the preseason as a predictor of how active the season will be. However, how well are SSTs in May correlated with seasonal activity?

Decided it'd be fun to try to find this out using the NCEP/NCAR SST reanalysis from 1948-2019 and the seasonal ACE values for those years. I took a look at a whole bunch of points in the Atlantic and Eastern Pacific, and for each point, got the mean SST in a 5x5 degree gridbox centered on that point for each year and then compared it to the total seasonal ACE, getting an r^2 value indicating the strength of a (linear) correlation for each point.

If you were to guess where Atlantic SSTs in May were most strongly correlated with ACE, what would you guess? Did you guess the eastern Atlantic between Cape Verde and the Canary Islands? It took a very long while, but here are the results. Red shades indicate a positive correlation (warmer SSTs in May correlates with more seasonal activity) and blue shades indicate a negative correlation (cooler SSTs in May correlates with less seasonal activity). The darker the shading the stronger the linear correlation.

Given how many variables are involved in determining seasonal activity, it's no surprise that the correlation between May SSTs and ACE, at least numerically, is rather weak. r^2 values were at most about 0.3, which definitely isn't strong. But perhaps the spatial distribution of where things are more strongly or weakly correlated may tell us something about where to look in May for SSTs.

There's two maps here. I don't want to be misleading with the colors, so I wanted to emphasize first that the numerical correlation is rather weak; the first map has softer shading to reflect that. The second map has darker shading to bring out the spatial details, but don't confuse the harsher colors for a strong correlation necessarily - the r^2 values are still low overall.

890KB. Source: Generated myself using QGIS and data from ESRL


908KB. Color scale enhanced here to bring out spatial details, but don't confuse the darker shading for a necessarily strong correlation. Source: Generated myself using QGIS and data from ESRL


The way I produce this data takes a rather long time, but I'll probably make additional maps for other months and other regions later.

This was a great post. Thank you. It was an interesting analysis and doesn’t try to say too much. Sea surface temperature in May does not correlate well to ACE in a season. No more, no less, but in a convincing way.


Sent from my iPhone using Tapatalk

[GrayLancer18]

While it has been widely documented that SSTs over the MDR are cooler than 2005, 2010, and 2017, I decided to take a look at some other hyperactive (153+ ACE) seasons since 1995 and see how they compare to 2020. I used a monthly average from April 20-May 19 to eliminate noise. The MDR is pretty similar to 2004, and actually warmer than 1999 and 2003 over the same time span.

Here's 2020 for reference:
https://i.imgur.com/eLYi0r2.gif

What's haunting about this is that 2020 has the warmest GOM of all.

It's easy to get fixated in the MDR but he two costliest hurricanes in history peaked in the GOM. There's always the chance that an MDR system can recurve without hitting land but once one enters the Gulf it will make landfall no matter the ridging or trough that picks it.

[FireRat]

Amazing post CyclonicFury!

2004 is a great example of why we can't tell it will be a slow season just by SSTs.
Heck, even 1996 which had quite cold waters in the western Atlantic (probably because of that brutal winter) was quite a show. 1996 was tied with 2004 with 6 MAJORS, and the year featured 9 hurricanes and 13 overall named storms. 1996 was another beast of a season, and by the water temps that May ppl wouldn't have imagined the way it turned out.