This is a fairly detailed report on Jupiter’s atmospheric activity covering the last 2/3 of the 2019 apparition, which can serve as a draft for our final report.  It is based on amateur images  but also incorporates some results from JunoCam.  Apart from the main report, it includes:

Zonal Wind Profile, derived from Hubble images on June 26-27 by Marco Vedovato, giving speeds for the major jets.

Appendix:   ‘Towards a new three-year weather forecast for Jupiter’  (text also printed below)

Supplement:  JUPOS charts for the major domains, annotated.  (Note that these use our standard convention with L2 increasing to the right, so they are aligned with maps having south up, opposite to the maps and images in the main report.)

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The report is in these files:

Text of report (PDF):    Jup-2019_Report-no-9_text.pdf

Miniatures of figures (PDF):    Jup-2019_Report-no-9_Minifigs.pdf

Full-size figures (ZIP):   Report-no-9_Figures.zip

Supplement — JUPOS charts (ZIP):    Report-no-9_Supplement_JUPOS-charts.zip

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Figure 1: 

Summary

This is a fairly detailed report covering the last 2/3 of the 2019 apparition, which can serve as a draft for our final report.  It is based on amateur images  but also incorporates some results from JunoCam.

A Zonal Wind Profile is presented, derived from Hubble images on June 26-27, giving speeds for the major jets.

North and south polar projection maps are presented, from both amateur and JunoCam images; features were tracked up to ~72°N and ~75°S.  A large AWO has been tracked in the N5 domain.

N2 domain:  Five anticyclonic ovals in the NNTZ were tracked; one AWO has turned reddish and a new small reddish oval appeared.  Changes in NNTB segments are documented. 

The NNTBs jet outbreak is still active.

N. Temperate domain:  Most of the NTB is very pale, but there is still a rifted sector, which generates the dark N. Temperate Disturbance f. it.

The NTBs jet speed is measured and predicts a new super-fast outbreak in 2021.

N. Tropical domain:  The NTropZ is now all white.   The NEB is a dark brown belt of normal width, with no major rifts until late November. 

On the NEBs, a regular array of typical large dark formations was prominent in 2019, with DL1 around +5 deg/mth.  There were also some short, faster tracks, e.g. DL1 ~ -20 deg/mth.

Equatorial Region :  The strong ochre colour of the EZ was the most impressive feature of this apparition.  It had begun in spring, 2018, and was most intense for the first six months of 2019.  Since the summer, it may be fading.

S. Tropical domain:  The SEB consists of three fairly narrow dark components.  Unusually, the northern half of the belt is largely quiet and whitened (esp. f. the GRS), while the southern half shows normal activity of the post-GRS rifting and SEBs jetstream spots.   There are two ‘white barges’ in southern SEB, both probably derived from earlier brown barges.

There have been many retrograding SEBs jet spots (rings), with normal speeds for the jet, as well as slower-moving wave-trains.

GRS & flakes:  A remarkable phenomenon in 2019 was the repeated emergence of ‘flakes’ of red, methane-bright material from the GRS, typically induced at its f.(W) end several days after a retrograding SEBs ring had entered the Red Spot Hollow at the p.(E) end (as described in our previous reports up to no.7).  As of late July, there were no further rings on the SEBs for a long distance, and indeed no more flakes were produced in August.  Then, a series of 7 SEBs rings arrived from Sep.8 to Oct.17, and each one apparently led to a flake appearing at the f. end 3-6 days later.  Also, from Sep.21 onwards, small protrusions emerged from the p. end of the GRS, probably flake material that had travelled round the S side. These phenomena were probably similar to those recorded at higher resolution earlier in the year. 

The GRS had shrunk in April-May, and in June it was very small, only 12.1 deg long.  Its length then recovered somewhat, reaching 14.0 deg. in late Oct.  Its  mean drift rate throughout 2019 was DL2 = +1.9 deg/mth, unaffected by the flaking events.

The dark grey-brown S. Tropical Band formed in April, and it elongated rapidly and combined with the dark STB(N) p. oval BA so as to extend almost completely around the planet in July. Then it began to decline, and it faded away in August.  Two anticyclonic rings had formed on it p. the GRS in May-July, and persisted up to Oct.

S. Temperate domain:  Oval BA is still white, and fast-moving (mean DL2 = -14.2 deg/mth), with a short dark turbulent STB segment f. it, which presumably generates the dark spotty bands in STZ Sf. it and on STB(N) Np. it.  The STB Spectre had low contrast and continued to lengthen rapidly, attaining a length of 110° by Nov.3, when JunoCam confirmed its structure.

S2 domain:  There are still 8 AWOs.  Two of the cyclonic intervals between them were white oblongs.  In other intervals, we document dark bars and turbulent regions.

S3 domain:  We track four AWOs in 2019, and some retrograding dark spots.

An impact flash was detected on 2019 August 7, the sixth since 2010.

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Appendix:  Towards a new three-year weather forecast for Jupiter [as of 2019 Sep.]:

Our improved understanding of Jupiter’s large-scale climatic cycles now enables predictions for some phenomena and possibilities for others.  In early 2015 I ventured a three-year forecast, and the predictions therein were largely fulfilled, although with significant differences in timescales.  This success was largely because there were indications that several large-scale cycles were beginning at that time.  In 2019 this is not the case so it is more difficult to make predictions.  Nevertheless, at the EPSC in Geneva in 2019 Sep. I presented the following thoughts.

The NTB:  A new NTBs jet outbreak is likely because (i) they typically recur at 5-year intervals; (ii) the NTB is now faded; (iii) the jet has recovered to an intermediate  speed.  Therefore, I expect a new NTBs jet outbreak in 2021.

The NEB is in a fairly normal state which could last for some years, or a new cycle of broadening to the north could start any time from 2020 onwards.  These ‘NEB expansion events’ typically occur every 3-5 years; the most recent occurred in 2017.  The belt has now retreated again.  A new expansion event could begin in the next 2 years, or the series may have finished.

The EZ coloration event is the most intense since 1989-91.  Previous intense episodes like this one have lasted between ~2.5 and 5 years. This episode began in spring, 2018; is maximal in 2019; and may now be starting to fade. So it is likely to continue at least into 2020, but it could terminate any time in the next few years.

The SEB is in an unusual state with the north half largely whitened but the south half showing normal convective and jet activity, so prediction is uncertain.  The last SEB Fade/Revival cycle was in 2010.  The belt does not appear to be entering a fully inactive and faded state, but it could do so with only a few months warning. Even if not, a mid-SEB outbreak could erupt any time and would be much the same as a SEB Revival.

The STB:  There are presently just two STB structured sectors: the STB Spectre and the complex around oval BA.  The Spectre is very elongated & low-contrast; it will catch up with the dark segment f. oval BA in 2020, and may transform turbulently into a dark STB segment as the STB Ghost did in 2018, but given its exceptional length, it might behave differently.  A new structured sector is expected to form soon, probably tens of degrees p. oval BA.

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