Weak La Nina Exists Till The End Of April 2018 – એપ્રિલ આખર સુધી સામાન્ય લા નિના હજુ અસ્તિત્વ માં છે

ENSO Status on 4th May 2018

Weak La Nina Exists Till The End Of April 2018.

2018 એપ્રિલ આખર સુધી સામાન્ય લા નિના હજુ અસ્તિત્વ માં છે.

 

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 OND 2017 -0.9ºC, NDJ 2018 -1.0ºC, DJF 2018 -0.9ºC, JFM 2018 -0.8ºC and FMA 2018 -0.6ºC. La Nina event was already in existence and since the latest 3-monthly seasonal ONI Index is less than or equal to -0.5ºC it fulfills the NOAA criteria for continuance of La Nina at the end of April 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 Continuance Of La Nina For FMA 2018 Season

 

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   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   26.50   27.21   -0.71
2018   4   27.27   27.73   -0.46

 

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

 

As per BOM, Australia:

The 30-day Southern Oscillation Index (SOI) to 2nd May 2018 was +2.4, while the 90-day SOI remains within the neutral range.

 

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

Recent (preliminary) Southern Oscillation Index values as per The Long Paddock – Queensland Government.

30 Days average SOI was +4.02 at the end of April 2018 and was +0.85 on 4th May 2018 as per The Long Paddock – Queensland Government and 90 Days average SOI was +2.55.

 

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

 

 

 

 

 

Summary by: Climate Prediction Center / NCEP  Dated 30th April 2018

ENSO Alert System Status: La Niña Advisory

La Niña conditions are present.*
Equatorial sea surface temperatures (SSTs) are near-to-below average across the east-central and eastern Pacific Ocean.
La Niña is expected to transition to ENSO-neutral during the April-May, with ENSO-neutral then likely (greater than 50% chance) to continue through the Northern Hemisphere summer 2018.

 

As per BOM -Australia 24th April 2018

ENSO outlooks

All earlier updates are listed below:

Click here for Update “Full Fledged La Nina Event Has Developed At The End Of March 2018”

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”

 

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