Colorado (and Interior Southwest) forecasts - new edition


Outline for SWcasts webpage (updated on February 12th, 2012)

This webpage consists of four main parts:

1. Recent summary of the status and outlook for ENSO (El Niño/Southern Oscillation), what this means for Colorado in particular, CPC-based climate forecasts, as well as my latest SWcasts, as presented at the Colorado Water Availability Task Force meeting (18 January 2012);

2. Latest ENSO conditions, CPC climate forecasts, and related links;

3. Executive Summary of this webpage as well as latest SWcasts forecast map;

4. Archive access to previous SWcasts.

The most recent SWcasts are based on observational data through December 2011. They are supported through the Colorado Water Conservation Board which also posts my latest forecast information under Long Term Weather outlook, as well as the National Integrated Drought Information System NIDIS. I will update this website at least on a seasonal basis. If you have any questions about SWcasts, please contact me at Klaus.Wolter@noaa.gov

You are welcome to use any of the material from this website, but proper acknowledgment would be appreciated, especially when referring to figures, forecasts, and assessments unique to this website. PROPER ACKNOWLEDGMENT should state that the used material "was provided by Klaus Wolter at NOAA-ESRL PSD, Boulder, Colorado, from his website at http://www.esrl.noaa.gov/psd/people/klaus.wolter/SWcasts/". The forecasts presented here are experimental - users are cautioned that no responsibility for any losses can be assumed by NOAA-ESRL PSD.


Latest presentation at the Colorado Water Availability Task Force meeting

Seasonal Outlook into early 2012

This presentation summarizes my thoughts on the status and outlook for ENSO (El Niño/Southern Oscillation), what this means for Colorado in particular, Climate Prediction Center-based climate forecasts, as well as my latest SWcasts, as presented at the Colorado Water Availability Task Force (WATF) meeting on 18 January 2012. I will always post my latest WATF presentation at the above link. Click on the "Archive" button below to find earlier SWcasts, pdfs of earlier WATF presentations (incomplete for now), as well as verification statistics since at least 2004.


Current ENSO conditions, and CPC climate forecasts (links)

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SSTPLOT

Recent sea surface temperature (SST) and wind conditions in the tropical Pacific from Australia to just west of South America. They are discussed in my presentation above, however, this particular figure has been updated to reflect the most recent conditions. This figure is updated daily at the TAO/TRITON website.

Since this figure reflects conditions over the last five days, the reader may be interested in an ENSO discussion that pays more attention to the longer time scales of this phenomenon. My monthly updated Multivariate ENSO index provides for this by the end of the first week of each month, in time for this SWcasts update, and features a comparison figure of similar ENSO situations in the Multivariate ENSO Index sense here.

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iriplot

Latest comparison plot of 19(!) dynamical and 8 statistical model forecasts for east-central Pacific tropical SST anomalies. For those models that are run in ensemble mode (like the ECMWF forecast - note that the one shown here is from the previous month), this graph shows the average outcome. This figure is taken from the ( IRI ENSO model website) that is updated on the third Thursday of every month, in time for last month's update to this website.

Compared to December 2011, a clearer end to the current La Niña event is in sight, with more than 50% of the dynamical models, and exactly 50% of the statistical models ending it by late spring (April-June 2012).

Meanwhile, the European coupled model forecast for central Pacific equatorial SST anomalies is predicting neutral ENSO conditions by June (not shown here). I consider this model the 'gold standard' for all ENSO forecast models out to six months. Check out the ( ECMWF seasonal forecast website) for this product that gets released to the general public in the 2nd half of each month.

For an independent interpretation of the current situation, I recommend reading the latest NOAA ENSO Advisory which represents the official and most recent Climate Prediction Center opinion on this subject. My own monthly updated ENSO discussion is sometimes in agreement with the NOAA ENSO advisories, and sometimes not. The reader is referred to the latter website to get my point of view.

The most recent U.S. government (CPC) precipitation forecast for February 2011 through April 2012 (below) is mostly based on their 'consensus tool' that summarizes statistical CPC forecasts as well as their dynamical Coupled Forecast System (CFS), with a net outcome of "below normal" (enhanced chances of below-normal, compared to near-normal, and above-normal precipitation amounts) for much of the southwestern U.S., including most of Colorado (only the northwestern corner of Colorado shows neutral odds ("EC"). Both seasonal temperature and precipitation forecasts by CPC are posted on their seasonal outlook website that is updated on the third Thursday of every month, and discussed in my WATF presentation from last month. Note that the Climate Prediction Center (CPC) issues seasonal forecasts out to 15 months, not just the next season.

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cpcprecip plot

Executive Summary (updated on February 10th, 2012)

1. La Niña has made a come-back, confirming my long-lead outlook from late 2010. It is weaker than last winter, and its impacts have been less typical for this ENSO phase than in 2010-11 in the contiguous U.S.

2. Colorado's mountain snowpack has reached its typical half-way point (late January/early February) at below-normal size, especially in the northern and central mountains. A La Niña-typical wet spell in mid-January rescued it from an even worse fate, but was not strong enough to reverse the deficits incurred in November and December 2011. Since October through December precipitation contributes disproportionately to Colorado River runoff, we will definitely not see anything close to last year's high runoff. By contrast, cities along the northern Front Range have been hit by near-record snowfall in late December and record-snowfall in early February, although this has not translated into a surplus in the South Platte Basin at elevations above 10,000'.

3. My final forecast for January through March 2012 reverted back to a mostly dry outlook for the southwestern U.S., including most of our mountain ranges, except for the eastern San Juans and Sangre de Cristos. Northeastern Colorado remained undecided as in earlier versions of this forecast season: the odds for either wet or dry conditions in this season are higher than for a near-normal outcome. January was very dry in much of northeastern Colorado, while February got off to a roaring start, tipping the scale towards that wet outcome.

4. Bottomline: Considering that 2nd year La Niña seasons are often drier than during the 1st year, the current outlook for January through March 2012 confirms that scenario for 2012 for much of our mountains. Given the current deficit of 10-40% in our state's snowpack, it would take an even larger positive anomaly in the next seven weeks to recover this lost ground by April 1st. My current estimate for Colorado River runoff in 2012 is similar to 2010 when it ended up between 12-13 MAF for naturalized Water Year flow (or about 8MAF less than in 2011).

The forecast map below shows the calibrated shifts in the tercile probabilities for January through March 2012:

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plot

Forecasted shifts in tercile probabilities for January through March 2012. In order to be shown on this map, a forecast tilt in the odds has to reach at least 3% either towards wet, dry, or near-normal. Shifts towards the wettest (driest) tercile are indicated in green (red), with a green plus sign for shifts between +3% and +5%, and a red minus sign for equivalent shifts towards the negative. Tilts towards near-normal are indicated by the letter "N", if at least by 3%. A question mark denotes a forecast with a greater likelihood of being either wetter OR drier than near-normal at the expense of near-normal odds. Positive or negative shifts of over 5% are contoured in 5% increments. If any shift reaches 10%, it is considered significant, even if recent verification skill has been wanting.


Archive access to previous SWcasts

To repeat from the beginning of this webpage: This forecast guidance is experimental, and should be used with caution. NOAA-ESRL PSD cannot assume any responsibility for losses incurred related to them.

To access an archive of earlier public experimental forecasts and verifications, click on the season and lead-time of interest, once you get to the respective directory. Average Heidke Skill scores for each forecast season are listed here. I will update this archive soon to include all issued forecasts from Water Year 2000 through 2011.

I am open to suggestions on what should be accessible in this archive. My current plan is to to include as many as pdf's of WATF presentations as are still available, back to 2004 when I started giving powerpoint presentations to that audience. For instance, the six remaining powerpoint presentations in 2004 can be found here. IN 2011, WATF talks were given in February, March, April, June, September, and November.


Questions about this webpage should be addressed to:
(Klaus.Wolter@noaa.gov), (303) 497-6340.