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Real-time SOI Data

Numerical data from here and values are calculated using the 1887-1989 base period. This information is usually updated every weekday at 2:00pm (AEST), public holidays excluded.

Date Pressure at Tahiti (hPa) Pressure at Darwin (hPa) Daily value 30-day average SOI 90-day average SOI
24 Oct 2017 1015.87 1011.40 10.18 (-0.91) 13.33 (+0.09) 7.32 (+0.10)
23 Oct 2017 1014.86 1010.25 11.09 (+10.25) 13.24 (+0.16) 7.22 (+0.17)
22 Oct 2017 1013.82 1010.80 0.84 (-2.51) 13.08 (-0.13) 7.05 (-0.01)
21 Oct 2017 1014.71 1011.30 3.35 (-5.54) 13.21 (+0.18) 7.06 (-0.02)
20 Oct 2017 1013.92 1009.65 8.89 (-0.91) 13.03 (+0.55) 7.08 (-0.07)
19 Oct 2017 1012.66 1008.25 9.80 (+1.36) 12.48 (+0.55) 7.15 (-0.19)
18 Oct 2017 1012.05 1007.85 8.44 (-5.1) 11.93 (+0.33) 7.34 (-0.19)
17 Oct 2017 1011.54 1006.55 13.54 (-0.77) 11.60 (+0.57) 7.53 (-0.01)
16 Oct 2017 1012.26 1007.15 14.31 (-7.41) 11.03 (+0.62) 7.54 (+0.07)
15 Oct 2017 1013.21 1006.95 21.72 (+6.06) 10.41 (+0.62) 7.47 (+0.09)
14 Oct 2017 1013.27 1007.95 15.66 (+10.70) 9.79 (+0.15) 7.38 (+0.02)
13 Oct 2017 1012.56 1008.90 4.96 (-0.32) 9.64 (-0.23) 7.36 (-0.13)
12 Oct 2017 1013.01 1009.30 5.28 (-14.12) 9.87 (-0.07) 7.49 (-0.09)
11 Oct 2017 1013.85 1007.95 19.40 (+0.45) 9.94 (+0.18) 7.58 (+0.24)
10 Oct 2017 1014.13 1008.30 18.95 (+14.31) 9.76 (+0.25) 7.34 (+0.36)
9 Oct 2017 1012.56 1008.95 4.64 (-3.16) 9.51 (+0.13) 6.98 (+0.18)
8 Oct 2017 1013.50 1009.40 7.80 (-13.66) 9.38 (+0.45) 6.80 (+0.07)
7 Oct 2017 1015.67 1009.45 21.46 (+1.74) 8.93 (+0.69) 6.73 (+0.13)
6 Oct 2017 1016.00 1010.05 19.72 (+6.70) 8.24 (+0.20) 6.60 (+0.08)
5 Oct 2017 1015.86 1010.95 13.02 (-5.99) 8.04 (-0.31) 6.52 (+0.05)
4 Oct 2017 1016.79 1010.95 19.01 (-6.9) 8.35 (+0.19) 6.47 (+0.10)
3 Oct 2017 1017.71 1010.80 25.91 (-3.16) 8.16 (+0.79) 6.37 (+0.14)
2 Oct 2017 1018.00 1010.60 29.07 (+15.73) 7.37 (+0.73) 6.23 (+0.24)
1 Oct 2017 1016.21 1011.25 13.34 (+2.29) 6.64 (+0.48) 5.99 (+0.24)
30 Sep 2017 1016.13 1011.95 11.05 (-4.16) 6.16 (+0.76) 5.75 (+0.29)
29 Sep 2017 1016.23 1011.35 15.21 (+3.68) 5.40 (+0.64) 5.46 (+0.25)
28 Sep 2017 1015.76 1011.50 11.53 (+/-0.00) 4.76 (+0.07) 5.21 (+0.20)
27 Sep 2017 1016.11 1011.85 11.53 (-4.1) 4.69 (+0.20) 5.01 (+0.18)
26 Sep 2017 1016.30 1011.35 15.63 (+0.95) 4.49 (+0.49) 4.83 (+0.19)
25 Sep 2017 1015.99 1011.20 14.68 4.00 4.64




Charts: 2017 | 2016 | 2015 | 2014 | 2013 | Source: The State of Queensland, Australia

ENSO Wrap Up (Source: here)

Issued on 24 October 2017

La Niña WATCH activated

The El Niño Southern Oscillation (ENSO) is currently neutral. However, models suggest the tropical Pacific Ocean will continue to cool, making the chance of a La Niña forming in late 2017 at least 50%; around double the normal likelihood. While this means the Bureau's ENSO Outlook has shifted to La Niña WATCH, rainfall outlooks remain neutral due to competing climate drivers.

Following a brief period of warming, tropical Pacific surface waters cooled significantly in the past fortnight, and hence the central to eastern tropical Pacific Ocean is now generally cooler-than-average. Atmospheric indicators of ENSO, including the Southern Oscillation Index (SOI), trade winds and cloudiness near the Date Line, are also approaching La Niña levels.

Seven of the eight international climate models surveyed by the Bureau suggest that sea surface temperatures will reach or exceed La Niña thresholds by November 2017. However, indicators need to remain at La Niña levels for at least three months to be considered an event. This is forecast by six of the eight models. If a La Niña does occur this year it is likely to be short and weak, as sea surface temperatures are forecast to warm again in early 2018, as the austral autumn is the time when La Niña events normally decay.

The Indian Ocean Dipole (IOD) is currently neutral. All six international climate models indicate neutral conditions will continue through 2017. Indian Ocean Dipole events are typically unable to form between December and April due to the influence of the monsoon trough over the tropical Indian Ocean.

La Niña events typically bring above average rainfall to eastern Australia during late spring and summer. However, given the competing influence of other climate drivers (weakly warm waters to the north of Australia, and cooler waters in the eastern Indian Ocean), current climate outlooks do not favour widespread rainfall across Australia for November to January. Weak La Niña events in summer can also produce heatwaves in southeast Australia.


SOI summary:

The 30-day Southern Oscillation Index (SOI) to 22 October is +13.0 (90-day value +7.1), well within the La Niña value range. 30-day SOI values have been above La Niña thresholds for three weeks.

Sustained positive values of the SOI above +7 typically indicate La Niña while sustained negative values below −7 typically indicate El Niño. Values between +7 and −7 generally indicate neutral conditions.


Sea surface temperature summary:

For the week ending 22 October, sea surface temperatures (SSTs) were cooler than average along the equator in the central and eastern Pacific Ocean, and to the south of the equator along the coast of Peru in South America. There has been a significant cooling of SSTs in the central to eastern equatorial Pacific over the past two weeks, resuming the cooling trend seen since mid-winter. NINO3 and NINO3.4 have cooled by 0.6 °C and 0.5 °C respectively, compared to two weeks ago.

Weak warm anomalies persist across much of the western Pacific, extending well into both the north and south of the basin. Stronger warm anomalies continue to the south of Japan, and along large parts of the southeast coast of Australia.

All of NINO3, NINO3.4, and NINO4 have cooled during the past fortnight. Latest values for the week ending 22 October are: NINO3 −0.6 °C, NINO3.4 −0.5 °C, NINO4 −0.1 °C.

Persistent values below −0.8 °C are typically indicative of La Niña, while persistent values above +0.8 °C are typical of El Niño.


ENSO outlooks:

International climate models surveyed by the Bureau indicate that further cooling of equatorial Pacific Ocean sea surface temperatures is expected during spring and summer. Seven of the eight models anticipate that SSTs will reach or surpass La Niña thresholds during November. Six of these models indicate that these SSTs will persist long enough to be classified as a La Niña event; persistence for three months is generally considered the minimum length required to be considered an event.

Late forming La Niña are rare, but not unheard of. You can read about the evolution and effect of previous events in our La Niña Summaries.

Last Accessed: Tue Oct 24 2017 19:05:20 HKT
Last Modified: Sun Jul 10 2016

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