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The plot below shows the forecast evolution plot for 24-hour precipitation (31 ecember 00UTC - 1 January 00UTC) a 0.5x0.5 box centred on Male. Concatenated 6-hour forecasts - green dot, ENS control –red, ENS blue box-and-whisker, Model climate – cyan box-and-whisker. Ensemble mean as black diamonds. Triangle marks the maximum in the model climate based on 1800 forecasts. While the wetter-than normal signal is visible also here, the extreme was only captured in the last forecast.
ecPoint
Figures in the table below illustrate ecPoint performance for this case.
On the CDFs we see the standard wet tail elongation that characterises ecPoint post-processing. X-axis values for the blue ecPoint line show that at these short-medium-range lead times rainfall of order 178mm/12h was low probability, but not out of the question. Bias correction at the gridbox scale (green versus red lines) acts to slightly reduce the totals, except at very short leads when it does little to change them. For large rainfall totals in the forecast one tends to see more of a bias correction to lower values. The mitigating factor here is very probably the consistently rather high CAPE values (denoted by values of typically 3 in the fourth digit of the weather types on the CDF tables). Meanwhile one can see that the model is diagnosing a mix of convective and large scale rainfall; in some members it is much more convective, in others it is much more large scale. This is denoted by the values 4 and 1 respectively in the first digit of the weather types.
On the map plots, showing probabilities of gauge measurements exceeding 100mm/12h, we see that as the event approached the signal slowly but surely increased. And there is not much jumpiness. It would be wrong to criticise the forecasts because the highest probabilities are not over Male. This all suggests that these products could have been used as the basis for early warnings of extreme rainfall. One caveat is that we have not looked at a lot of cases - if such signals occur regularly in this area the false alarm count would be high. Nonetheless global verification suggests the probabilities should be fairly reliable.
| DT & lead time: | 0Z 28th (T+72-84) | 12Z 28th (T+60-72) | 0Z 29th (T+48-60) | 12Z 29th (T+36-48) | 0Z 30th (T+24-36) | 12Z 30th (T+12-24) | 00Z 31st (T+0-12) |
CDFs for 12h rainfall for Male: Valid 00-12UTC 31st when about |
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Probabilities of point rainfall (as measured by a gauge) exceeding 100mm in 12h, from ecPoint: X on the first plot is Male. |
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3.4 Monthly forecasts
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