Is not only the North Atlantic that is slow / Global Northern Hemisphere is below normal

[cycloneye]

Many had been discussing about when the North Atlantic will turn active as the calender says August 16 when normally the most active part of the season is starting.However,EPac and WPac are not above normal in their ACE numbers so the question to the members and especially to our pro mets is (What is going on globally that things are slow?)

Below are the ACE numbers as of August 16 for each basin and the Northern Hemisphere data:

North Atlantic ACE so far=3.6 vs (13.0) the normal

EPac ACE so far=46.1 vs (58.0) the normal

WPac ACE so far=76.8 vs (96.3) the normal

NIO ACE so far=33.8 vs (8.2) the normal / Only basin above normal.

Northern Hemisphere ACE so far=160.3 vs (175.5) the normal

Source of ACE per Phil Klotzbach.

http://tropical.atmos.colostate.edu/Realtime/

[1900hurricane]

¯\_(ツ)_/¯

[StruThiO]

Seems like the wpac quiescence has been characterized by:

1. Expansive, dominating subtropical ridge or
2. Mei-yu induced shear or
3. TUTT induced shear

In the epac, many systems thus far have gotten sheared out (great Hawaiian shear ftw). Additionally, I believe air has been drier than normal in parts of the basin.

And don't even get me started on the ATL

[Ntxw]

Sometimes the Earth just likes to keep things at a balance. Beyond just the indicators we all like to pick and narrate, perhaps it's simply a seesaw effect. 2018 was a very high ACE yield year across the globe in just about all basins as the planet was pumping strong system after strong system. 2019 on the other hand just seems out of gas.

[cycloneye]

Another 2013 globally?

[Emmett_Brown]

Sometimes the Earth just likes to keep things at a balance. Beyond just the indicators we all like to pick and narrate, perhaps it's simply a seesaw effect. 2018 was a very high ACE yield year across the globe in just about all basins as the planet was pumping strong system after strong system. 2019 on the other hand just seems out of gas.

That would make sense... however, globally, we are actually above normal for ACE 384 vs 354 usually observed by this point, due mostly to the very active S Hem season that just recently ended.

[Hammy]

Another 2013 globally?

Was wondering the same, if there's some at-the-time unseen factor that's keeping one pattern in place for so long.

[USTropics]

Technically the Northern Hemisphere is at 95% of normal YTD (year to date) ACE, but that includes a very over-performing North Indian (35 ACE, YTD for climo is just 7; ~500% above normal). Narrowing this down to just EPAC/CPAC/WPAC/ATL, adding up all the ACE values YTD, we have 89.45 in WPAC, 47.59 in EPAC/CPAC, and 3.49 in ATL (total of 140.58). YTD for climo is 101 in WPAC (88% of normal YTD), 58 in EPAC/CPAC (80% of normal YTD), and 14 in ATL (24% of normal YTD) for a total of 173. These 4 basins are currently at 81% of YTD climo ACE.

[Astromanía]

I talked personally with earth and she said that was tired from last season and want to take some break this season and I was ok with that decision but I told her please don´t troll us with phantom storms. She lied to me.

Sorry I'm bored

[Yellow Evan]

Another 2013 globally?

Was wondering the same, if there's some at-the-time unseen factor that's keeping one pattern in place for so long.

Keep in mind that 2013 wasn’t as quiet globally as often made out to be. The WPAC and NIO were very busy after like August that year.

[NDG]

If it wasn't for the two IO systems earlier in the year ACE will have been much lower than average for the northern Hemisphere ytd.

[1900hurricane]

Another 2013 globally?

Was wondering the same, if there's some at-the-time unseen factor that's keeping one pattern in place for so long.

Keep in mind that 2013 wasn’t as quiet globally as often made out to be. The WPAC and NIO were very busy after like August that year.

Very much this. It was a down year for sure, but it doesn't actually stand out particularly from many other years over the last decade and a half, which has generally been towards the inactive. 2007 and 2010 are the particularly slow years from both a global and NH standpoint, with both years having the two lowest NH ACE totals since 1977.



The jury is still out for this year globally. Things look bleak now, but as we saw in mid-September in the WPac in 2013 or late August in the NAtl in 2017, things can flip very quickly.

[Hammy]

What on earth happened in 1977?

[1900hurricane]

:uarrow: What on earth happened in 1977?

Looks like mostly a year of short lived weak storms based on the low NH ACE and low Tropical Storm Days (below). Even accounting for some underdone intensities in the early satellite era/pre-geostationary days in many of the basins, there just isn't enough TS Days to go around. Now, as to the reason for that is something I don't currently grasp, although I'm sure I could find some papers on the topic if I did a little research. 1977 is a very well-known globally down year in the tropics as far as I know.





Something I also should have mentioned is that JTWC does not consider its SH data to be of particularly good quality until 1985, so SHEM numbers before that might be a little sketchy, as you might have been able to tell in the early portion of the graphs I made.

[Emmett_Brown]

:uarrow: What on earth happened in 1977?

Looks like mostly a year of short lived weak storms based on the low NH ACE and low Tropical Storm Days (below). Even accounting for some underdone intensities in the early satellite era/pre-geostationary days in many of the basins, there just isn't enough TS Days to go around. Now, as to the reason for that is something I don't currently grasp, although I'm sure I could find some papers on the topic if I did a little research. 1977 is a very well-known globally down year in the tropics as far as I know.

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

https://i.imgur.com/8GBbR9B.png

Something I also should have mentioned is that JTWC does not consider its SH data to be of particularly good quality until 1985, so SHEM numbers before that might be a little sketchy, as you might have been able to tell in the early portion of the graphs I made.

Cool chart, thanks. One thing that sticks out to me (other than the surprisingly low number of TS days thus far globally), is that the SH just finished a pretty active year with approx 160 named storm days. Visually, you can see some correlation between SH and NH activity. For example there were only 6 years where the SH had as many TS days as 2019. And, in those years, the average NH named storm days is 304 (avg NH ACE for these years is 560). So far in 2019, the NH has around 90 TS days (maybe less, just going visually by your chart). So, if the correlation between SH and NH activity in prior 4+ decades holds up, we should expect at least 214 more named storm days in the NH before 2019 ends

[Ptarmigan]

:uarrow: What on earth happened in 1977?

Looks like mostly a year of short lived weak storms based on the low NH ACE and low Tropical Storm Days (below). Even accounting for some underdone intensities in the early satellite era/pre-geostationary days in many of the basins, there just isn't enough TS Days to go around. Now, as to the reason for that is something I don't currently grasp, although I'm sure I could find some papers on the topic if I did a little research. 1977 is a very well-known globally down year in the tropics as far as I know.

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

https://i.imgur.com/8GBbR9B.png

Something I also should have mentioned is that JTWC does not consider its SH data to be of particularly good quality until 1985, so SHEM numbers before that might be a little sketchy, as you might have been able to tell in the early portion of the graphs I made.

1977 was very quiet across all basins. The Southern Hemisphere was about average in number of storms forming.

1976-1977 was El Nino and had came off of an El Nino. Then El Nino came back for 1977-1978. They were weak El Nino's in both cases.

That would explain the North Atlantic, but not the East and West Pacific. Monsoon was possibly weak that time in the West Pacific.

[euro6208]

I don't think it's a good idea to compare the WPAC to the rest. A slow season for the WPAC can be an average or above for the rest. THis will confuse alot of people into thinking they are the same.

[NotSparta]

I don't think it's a good idea to compare the WPAC to the rest. A slow season for the WPAC can be an average or above for the rest. THis will confuse alot of people into thinking they are the same.

They're all below average though (except NIO), that's the point of this thread

[dexterlabio]

1977 was very quiet across all basins. The Southern Hemisphere was about average in number of storms forming.

1976-1977 was El Nino and had came off of an El Nino. Then El Nino came back for 1977-1978. They were weak El Nino's in both cases.

That would explain the North Atlantic, but not the East and West Pacific. Monsoon was possibly weak that time in the West Pacific.

A theory of my own still holds that the second-year weak El Nino tends to suppress tropical cyclone development in the Pacific rather than enhance it.

[al78]

Another 2013 globally?

Was wondering the same, if there's some at-the-time unseen factor that's keeping one pattern in place for so long.

Keep in mind that 2013 wasn’t as quiet globally as often made out to be. The WPAC and NIO were very busy after like August that year.

Lets not forget what happened in the Philippines in November 2013. It wasn't a quiet season for the residents of Tacloban. It's not over until it's over.