ENSO Status on 4th April 2018

Full-fledged La Nina Event Has Developed At The End Of March 2018.

માર્ચ આખરના વિધિવત “લા નીના” પ્રસ્થાપિત થયું.

The ONI is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO. Defined as the three-month running-mean SST departures in the Niño 3.4 region. Departures were based on a set of improved homogeneous historical SST analyses (Extended Reconstructed SST – ERSST.v4) and have now been updated to further improved homogeneous historical SST analyses (Extended Reconstructed SST – ERSST.v5). Explanation about ERSST.v5 is given here.

The SST reconstruction methodology is described in Huang et al., 2015, J. Climate, vol. 28, 911-930.
CPC uses current Climatology based on 1986-2015 which has been changed late last year from base years 1981-2010. Explanation about Climatology base years change is given here.

NOAA Operational Definitions for El Niño and La Niña, El Niño: characterized by a positive ONI greater than or equal to +0.5ºC. La Niña: characterized by a negative ONI less than or equal to -0.5ºC. By historical standards, to be classified as a full-fledged El Niño or La Niña episode, these thresholds must be exceeded for a period of at least 5 consecutive overlapping 3-month seasons.

CPC considers El Niño or La Niña conditions to occur when the monthly Niño3.4 OISST departures meet or exceed +/- 0.5ºC along with consistent atmospheric features. These anomalies must also be forecast to persist for 3 consecutive months.

Last five ONI Index are SON 2017 -0.7ºC, OND 2017 -0.9ºC, NDJ 2018 -1.0ºC, DJF 2018 -0.9ºC and JFM 2018 -0.8ºC. Since, five consecutive 3-monthly seasonal ONI Index are less than or equal to -0.5ºC it fulfills the NOAA Operational definition of a La Nina at the end of March 2018.

La Nina event 2017-18 has officially evolved at the end of March 2018 (JFM 2018). This La Nina event is the second consecutive La Nina event, the other being 2016-17 La Nina event that ended at the end of January 2017 (NDJ 2017).

Latest Oceanic Nino Index (ONI) Graph Showing Official La Nina Event Has Evolved JFM 2018

The Table below shows the monthly SST of Nino3.4 Region and the Climate adjusted normal SST and SST anomaly for last two years. Climate Base 1986-2015. ERSST.v5

Period    Nino3.4 ClimAdjust
YR   MON  Temp.ºC Temp.ºC ANOM ºC

2016   2   29.00   26.66    2.34
2016   3   28.90   27.21    1.70
2016   4   28.73   27.73    0.99
2016   5   28.24   27.85    0.39
2016   6   27.70   27.65    0.05
2016   7   26.82   27.26   -0.44
2016   8   26.28   26.91   -0.63
2016   9   26.15   26.80   -0.65
2016  10   25.98   26.75   -0.78
2016  11   25.95   26.75   -0.80
2016  12   26.10   26.65   -0.55
2017   1   26.12   26.45   -0.33
2017   2   26.68   26.66    0.02
2017   3   27.33   27.21    0.12
2017   4   28.04   27.73    0.30
2017   5   28.30   27.85    0.45
2017   6   28.06   27.65    0.41
2017   7   27.54   27.26    0.28
2017   8   26.70   26.91   -0.21
2017   9   26.29   26.80   -0.51
2017  10   26.15   26.75   -0.60
2017  11   25.74   26.75   -1.01
2017  12   25.62   26.65   -1.04
2018   1   25.58   26.45   -0.88
2018   2   25.98   26.66   -0.68
2018   3   26.44   27.21   -0.77

CPC considers El Niño or La Niña conditions to occur when the monthly Niño3.4 OISST departures meet or exceed +/- 0.5°C along with consistent atmospheric features. These anomalies must also be forecast to persist for 3 consecutive months.

Southern Oscillation Index

SOI Monthly graph up to March 2018 as per The Long Paddock – Queensland Government.

30 Days average SOI was +8.48 at the end of March 2018 and was +10.47 on 4th April 2018 as per The Long Paddock – Queensland Government and 90 Days average SOI was +4.39.

Summary by: Climate Prediction Center / NCEP  Dated 2nd April 2018

ENSO Alert System Status: La Niña Advisory

La Niña conditions are present.*
Equatorial sea surface temperatures (SSTs) are below average across the central and eastern Pacific Ocean.
A transition from La Niña to ENSO-neutral is most likely (~55% chance) during the March-May season, with neutral conditions likely to continue into the second half of the year.

As per BOM -Australia 27th March 2018

ENSO outlooks

All eight of the surveyed international climate models indicate equatorial Pacific sea surface temperatures are likely to continue warming over the coming months. While two models suggest NINO3.4 will meet La Niña thresholds in April, a neutral ENSO is the most likely outcome for the remainder of the southern hemisphere autumn and winter. The Bureau’s model predicts the equatorial Pacific will continue to warm throughout winter but remain within the neutral range.

 

Ashok Patel’s Final Note:
Using NOAA Criteria A Full Fledged La Nina has evolved in March 2018 with 3-monthly season JFM 2018 at -0.8ºC

Last five ONI Index are SON 2017 -0.7ºC, OND 2017 -0.9ºC, NDJ 2018 -1.0ºC, DJF 2018 -0.9ºC and JFM 2018 -0.8ºC. Since, five consecutive 3-monthly seasonal ONI Index are less than or equal to -0.5ºC it fulfills the NOAA Operational definition of a La Nina at the end of March 2018.

La Nina event 2017-18 has officially evolved at the end of March 2018 (JFM 2018). This La Nina event is the second consecutive La Nina, the other being 2016-17 La Nina event that ended at the end of January 2017 (NDJ 2017).

It is surprising that BOM Australlia on 27th March 2018 says “El Niño-Southern Oscillation neutral”

અશોક પટેલ ની નોંધ :

NOAA માપદંડ મુજબ વિધિવત La Nina 2018 માર્ચ આખરે પ્રસ્થાપિત થયું.

સળંગ 5 ત્રી-માસિક સીઝન માં ONI ઈન્ડેક્સ -0.5°C અથવા તેનાથી નીચે રહેલ છે, જેમ કે SON 2017 at -0.7°C, OND 2017 at -0.9°C,  NDJ 2018 at -1.0°C, DJF 2018 at -0.9°C and JFM 2018 at -0.8°C. એટલે NOAA માપદંડ મુજબ વિધિવત La Nina 2018 માર્ચ આખરે પ્રસ્થાપિત થયું.

ઓસ્ટ્રેલિયા ની BOM સંસ્થા ના 27 માર્ચ 2018ના બુલેટિન મુજબ ENSO ન્યુટ્રલ કન્ડિશન છે. તે તારણ સાથે હું અસહમત છું.

 

All earlier updates are listed below:

Click here for Update “La Nina Event 2017-18 Expected To Commence At The End Of March”

Click here for Update “Three Consecutive 3-Monthly Seasons Have Oni -0.5ºC Or Below”

Click here for Update “ENSO Neutral Conditions Prevails”

Click here for Update “ENSO Neutral Conditions Prevails With JAS 2017 ONI Index At -0.2ºC”

Click here for Update “Theoretically El Nino Not Possible During 2017”

Click here for Update “Theoretically El Nino Not Possible During The Indian Southwest Monsoon 2017”