Climate Sense

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bserving

, P

redicting

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rojecting

limate

onditions

Centres. In addition, consensus forecasts provided by

Regional Climate Outlook Forums (RCOFs) should be

considered whenever they are available.

Adaptation

and downscaling of these products to a scale pertinent

to the geographical scope covered by climate watches

is also required and should be based on scientifi-

cally sound techniques and methods. These products

are generally based on the probability of averages of

selected parameters (from weekly for monthly fore-

casts to thrice-monthly for seasonal forecasts) and

whether these averages are below, close to, or above

the local climatological references (normals).

The output of a climate watch system

includes:

initial reports outlining the ongoing and/or expected

climate anomaly; updated statements at user-agreed

time intervals informing on the progress of the

anomaly; and final statements stating the expiration

of the warning. The content, format and dissemina-

tion plan of climate watches should consider specific

purposes and geographical scope, as required by

the target users. It is also important that the system

includes a performance verification procedure, which

should be carried out systematically as an integral part

of the system operation. Users should be informed of

verification results on a regular basis. This builds trust

between the issuing organization and the users, as well

as constituting an assessment of the effectiveness of

the user-agreed criteria. Long-term, the verification

system provides a knowledge asset that can be used

for performance improvement.

System requirements

The issuing organizations (NMHSs) need to meet a

minimum set of requirements for operating a climate

watch. They should be able to provide the following

climate functions on an operational basis:

• Timely observations of current climate conditions

for their area of responsibility, as well as adequate

historical climate data

• Timely monitoring and analyses of current climate

anomalies

• Access to current global climate forecasts and the

technical capabilities to interpret and downscale

them to their region

Image: Omar Baddour

Example of a climate watch

Initial climate watch

Bureau of Meteorology National Climate Centre

CLIMATE WATCH FOR RAINFALL DEFICIENCY

Climate Watch valid for South Australia and western Victoria.

Issued on 3rd July 2008 – Valid until 4th August 2008

Areas of serious to severe rainfall deficiencies across South Australia and

western Victoria are likely to persist during the coming season. Most of SA and

western Victoria have recorded rainfall totals in the lowest decile range for the

thirteen-month period from 1st June 2007 to 30th June 2008. The outlook

for the next three months, July to September, derived from the Bureau of

Meteorology’s statistical forecast model, shows that the chance of exceeding

the median rainfall is only between 30 and 40% for these areas affected by

rainfall deficits. Outlook confidence for this forecast is moderate over northern

and central SA, with a skill level of around 60%. The confidence level for

western Victoria low, although in several areas the July to September rainfall

total would need to be decile 8 or higher for the deficits to be removed.

These figures meet or exceed the criteria for a rainfall deficit Climate Watch

for this region, being:

– Rainfall for the past three or more months: decile one or lower.

– Chance of rainfall being greater than the median: 40% or lower.

– Forecast skill score: 55% or greater.

Climate situation: Sea surface temperatures in the central equatorial

Pacific have gradually increased over the previous two months and are now

generally close to average. The final remnants of the 2007/08 La Niña event

continue to linger in the western Pacific, although the overall ENSO state is

rated as neutral. A majority of computer models in a recent survey indicated

that neutral conditions are likely to persist for the next three to six months.

However, these same models show that a positive dipole of Indian Ocean

temperatures (IOD) may persist for a few more months. This phase of the IOD

has been linked with reduced rainfall over central and southeastern Australia.

The monthly Climate Watch Africa bulletin provides analysis on important climatic factors including monsoon winds, rainfall and temperature

Source: Australian Bureau of Meteorology (BoM)