Presentation on theme: "PAGASA-DOST Presscon - 04 October 2010 Amihan Conference Room."— Presentation transcript:
PAGASA-DOST Presscon - 04 October 2010 Amihan Conference Room
Weekly averaged sea surface temperatures (left, °C) and anomalies (right, °C) for the past twelve weeks. SST analysis is the optimum interpolation (OI) analysis, while anomalies are departures from the adjusted OI climatology (Reynolds and Smith 1995, J. Climate, 8, 1571-1583). Period: 07 July – 22 Sep 2010 SST: Oceanic Indicator:
SOI is above La Niña thresholds The SOI has remained firmly positive and fairly steady in value for the past two weeks. The latest (27 September) 30-day SOI value was +25; the monthly value for August was +19. The SOI has been consistently positive since early April. Source: BOM, Australia SOI: Atmospheric Indicator:
NOAA Operational Definitions for El Niño and La Niña El Niño: characterized by a positive ONI greater than or equal to +0.5°C. La Niña: characterized by a negative ONI less than or equal to -0.5°C. 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 SST departures meet or exceed +/- 0.5°C along with consistent atmospheric features. These anomalies must also be forecasted to persist for 3 consecutive months.
ONI (Oceanic Niño Index) Red – El Niño Blue – La Niña Black - Neutral
International Prediction CentersSummary Climate Prediction Center / NCEP As of : 27 Sept 2010 La Niña conditions are present across the equatorial Pacific and is expected to last at least through the NH winter (DJF) 2010-11. Global Advisories International Research Institute (IRI), Columbia University, New York As of : 16 September 2010 Probabilities for La Niña conditions continue at 95% or more through the Dec-Feb season of 2010/11, and first drop to below 50% during Apr- June season of 2011. Bureau of Meteorology (BOM)- Australia As of : 29 Sept. 2010 La Niña remains well-established in the Pacific and is expected to persist into at least early 2011. APCC, APEC Climate Center, Busan, S. Korea As of: 27 Sept. 2010 The sea surface temperature anomalies in the central to eastern tropical Pacific have been colder than normal suggesting the La Nina phase.
Recent ENSO Conditions: (Sept. 2010) All key indicators of ENSO (cooler than average sea surface temperatures and the persistently stronger than average low-level winds, coupled with above average values of the Southern Oscillation Index (SOI), are at levels typical of La Niña. Based on recent trends and model forecasts, La Niña is likely to persist up to the early part of 2011. Expected Conditions:
The period covers the first half of the NE monsoon season. Tracks of tropical cyclone during this period are likely across central and southern parts of Luzon, and Visayas with secondary tracks over Northern Mindanao.
Summary: La Niña is expected to bring more than average (above normal) rainfall in most parts of the country during the OND season, based on the forecast. Expected number of tropical cyclones (TCs) on the remaining months (Oct-Dec) are about 5-8. Average tracks during OND season - likely across Central and Southern Luzon and Visayas.
Summary: Precautionary measures should be done by all concerned agencies against possible flooding, flashfloods and landslides in preparation for the expected La Niña to affect the country in the coming months. ***PAGASA will continue to monitor the development of the La Niña and the day-to-day associated rainfall/weather conditions that will affect the country. Updates will be issued as necessary.
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IMPACTS OF ENSO ON PHILIPPINE RAINFALL Legend: Severe drought impacts Drought impacts with major losses Moderate drought impacts Near normal to above normal condition Way above normal condition Potential for flood damage Severe flood damage RED colored years are EL NINO years, BLUE colored years are LA NINA years and BLACK colored years are NON_ENSO years
Historical El Niño and La Niña Episodes Based on the ONI computed using ERSST.v3b Highest El Niño ONI Value Lowest La Nina ONI Value JAS 1951 - NDJ 1951/52 0.8ASO 1949 – FMA 1951 -1.7 MAM 1957 – MJJ 1958 1.7MAM 1954 – DJF 1956/57 -2.1 JJA 1963 – DJF 1963/64 1.0ASO 1962 − DJF 1962/63 -0.8 MJJ 1965 – MAM 1966 1.6MAM 1964 – DJF 1964/65 -1.1 OND 1968 – MJJ 1969 1.0NDJ 1967/68 – MAM 1968 -0.9 ASO 1969 – DJF 1969/70 0.8JJA 1970 – DJF 1971/72 -1.3 AMJ 1972 – FMA 1973 2.1AMJ 1973 – MAM 1976 -2.0 ASO 1976 – JFM 1977 0.8SON 1984 – ASO 1985 -1.0 ASO 1977 - DJF 1977/78 0.8AMJ 1988 – AMJ 1989 -1.9 AMJ 1982 – MJJ 1983 2.3ASO 1995 – FMA 1996 -0.7 JAS 1986 – JFM 1988 1.6JJA 1998 – MJJ 2000 -1.6 AMJ 1991 – JJA 1992 1.8SON 2000 – JFM 2001 -0.7 AMJ 1994 – FMA 1995 1.3ASO 2007 – AMJ 2008 -1.4 AMJ 1997 – AMJ 1998 2.5 AMJ 2002 – FMA 2003 1.5 MJJ 2004 – JFM 2005 0.9 JAS 2006 - DJF 2006/07 1.1 MJJ 2009 – MAM 2010 1.8 NOTE: After updating the ocean analysis to ERSST.v3b, a new La Niña episode was classified (ASO 1962- DJF 1962/63) and two previous La Niña episodes were combined into one single episode (AMJ 1973- MAM 1976).
Rainfall Forecast Range in mm. per Province (Oct – Dec 2010)
Reanalysis of Vector Wind Composite Anomaly (Jun - Aug) Source: ESRL (Earth System Research Laboratory)