How Well Did The ECMWF Predict The Current Extreme Heat In The Western USA?

In my post on June 14 2012

Hot And Dry Forecast For The Western USA – A Possible Extreme Event

I presented the ECMWF forecast of an extreme heat wave for the western USA. Today’s post is to document how well they did. In my view, it is an outstanding example of how well weather prediction models, which are initialized with real world data, can predict out to 10 days and longer into the future. As just one example of the magnitude of the extreme event, Denver, Colorado matched its all time record June temperature of 104F on June 23.

The ECMWF forecast of 850 hPa temperature and 500 hPa geopotential height made on June 14 2012 00UTC for June 24 2012 00UTC  is reproduced below [click on the image for a clearer view.].

The actual verifying time analysis plots are presented below.

An important conclusion from this heat wave is dominated by regional atmospheric circulation patterns. While the northern hemisphere average positive temperature anomaly could add  to the extreme event, it would be only about +0.44C (+0.8F) [from UAH MSU for May 2012]. Human climate forcings undoubtedly influence atmospheric (and ocean) circulation patterns (e.g. see Pielke et al 2009), such extreme events cannot simply be related directly to “global warming”.

Below is the map of current Northern hemispheric 500 hPa height anomalies which documents the regional characteristic of this extreme event. It also shows that the extreme event was confined to the lower levels of the troposphere, as the 500 hPa anomalies over the western USA are actually dominated by the cold anomaly off of the west coast. It must be the transport north of hot air in the lowest levels of the troposphere from the desert plateau of northern Mexico and the southwest USA which produced the extreme heat (and very dry air) over the Colorado and adjacent areas.

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