Weather Discussion

4/24/12

ENSO UPDATE

Recent Evolution of Equatorial Pacific SST Departures (oC)

Longitude

Time

From September 2011- January 2012, below-average SSTs were evident across much of the equatorial Pacific Ocean.

Since February 2012, above-average SSTs have persisted in the eastern Pacific, while negative anomalies have gradually weakened in the central Pacific.

Niño Region SST Departures (oC) Recent Evolution

The latest weekly SST departures are:

Niño 4 -0.3ºC

Niño 3.4 -0.4ºC

Niño 3 0.1ºC

Niño 1+2 1.5ºC

SST Departures (oC) in the Tropical Pacific During the Last 4 Weeks

During the last 4-weeks, equatorial SSTs were below average in the central and east-central Pacific and above average in the eastern Pacific.

Weekly Central & Eastern Pacific Upper-Ocean (0-300 m) Average Temperature Anomalies

Positive subsurface anomalies were evident from March-July 2011. Negative anomalies developed in late July 2011. The negative anomalies began weakening in January 2012 and have recently become positive.

• During the last two months, negative subsurface temperature anomalies became near-average to above-average across the eastern equatorial Pacific.

• During the recent period, near-surface positive anomalies are evident in portions of the eastern equatorial Pacific.

Sub-Surface Temperature Departures (oC) in the Equatorial Pacific

Most recent pentad analysisLongitude

Time

Pacific Niño 3.4 SST Outlook

Figure provided by the International Research Institute (IRI) for Climate and Society (updated 17 April 2012).

• The majority of models predict ENSO-neutral conditions (Niño-3.4 SST anomalies between -0.5°C and +0.5°C) during the Northern Hemisphere spring, continuing through the remainder of 2012. • The average dynamical model forecast is slightly warmer than the statistical models and favor El Niño conditions during the last half of 2012.

Official Probabilistic ENSO Outlook(updated 5 Apr 2012)

ENSO-neutral is favored during the Northern Hemisphere spring and summer.

SST Outlook: NCEP CFS.v2 Forecast Issued 23 April 2012

The CFS.v2 ensemble mean (black dashed line) predicts El Niño conditions to develop by JJA 2012.(not PDF corrected)

Atmospheric Circulation over the North Pacific & North America During the Last 60 Days

200-hPa Wind

From mid-February to mid-April, above-average 500-hPa heights persisted over central and eastern North America, accompanied by above-average temperatures. During most of the period, below-average 500-hPa heights and temperatures were evident near the western coast of North America.

925-hPa Temp. Anoms. (oC)500-hPa Height & Anoms.

U.S. Temperature and Precipitation Departures During the Last 30 and 90 Days

30-day (ending 21 Apr 2012) temperature departures (degree C)

90-day (ending 20 Apr 2012) % of average precipitation 90-day (ending 21 Apr 2012)

temperature departures (degree C)

Last 30 Days

Last 90 Days

30-day (ending 20 Apr 2012) % of average precipitation

Big Convective Outbreak east of the Cascades

6 PM

Satellite

• http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?vis1km_west+/24h/2h

• http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?ir4km+/24h/

Lightning

• http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?ltnw+36

• http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?ir_ltng_common+48

Radar

• http://www.atmos.washington.edu/weather/radar.shtml

• http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?pdt_ncr+/24h/60m

• Otx• http://www.atmos.washington.edu/~ovens/lo

ops/wxloop.cgi?pdt_n0v+/24h/60m

Storm Total

• http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?ir_ltng_common+48

24-h precip

Heppner, June 14, 19033rd deadliest flash flood in U.S. history

(247)

Not a great forecast by WRF

• http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?mm5d3_pcp3+2012042312///3

• Good capehttp://www.atmos.washington.edu/~ovens/

loops/wxloop.cgi?mm5d2_mcape+2012042312//84/3

Nam only slightly better

HRRR Impressive

• http://rapidrefresh.noaa.gov/hrrrconus15min/jsloop.cgi?dsKeys=hrrr_15min:&runTime=2012042318&plotName=cref15min_t1sfc&fcstInc=15&numFcsts=61&model=hrrr&ptitle=HRRR%20Model%20Fields&maxFcstLen=15&fcstStrLen=-1&resizePlot=1&domain=t1&wjet=1

But no obvious trigger…