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MOGREPS-WFirst-guess Severe Weather Warnings for NSWWS
Estimating Impact – a Risk tool
The New National Severe Weather Warning Service (NSWWS)
• Alerts/warnings based on likelihood and impact• Alerts - issued more than 24 hours ahead• Warnings - issued up to 24 hours ahead
• Regionally varying impact thresholds• Alerts/warnings presented by shape areas on a map
rather that just by county area
Regional Impact Thresholds
Wind Gust RegionsRainfall Regions
Introduction to MOGREPS-W
MOGREPS-R Grid-Point Probs (≥ 70mph)
Severe Gales: 3rd February 2011DT: 06Z WED 02/02/2011 VT: 18Z THU 03/02/2011
MOGREPS-W Probability Severe Wind Gusts
(≥ 70mph)
Forecaster Issued Warnings of Severe
Wind Gusts (≥ 70mph)
Calibration of MOGREPS-WVerification of 40mph forecasts
Reliability Diagram(T+33h to T+42h forecasts)
Under-forecasting ~36mph forecasts might be best at forecasting 40mph events
Forecast Thresholds
All forecast thresholds are verified as if they are
forecasting 40mph events
September 2010 to February 2011 (6 month period)
Impact-based MOGREPS-WWeather Impact Matrix
High
Medium
Low
Very Low
Very Low Low Medium High
≥70mph ≥80mph ≥90mph
Example of MOGREPS-W
Wind Gust thresholds for the “Highlands and Islands”
≥1%
≥20%
≥40%
≥60%
Example of
MOGREPS-W probability thresholds
Impact
Lik
elih
oo
d
MOGREPS-W ExampleEx-hurricane Katia, 12th Sep 2011
MOGREPS-W first guess wind gust warning. Note small area of Red (but not enough to justify widespread)
Good agreement with warning issued by forecaster on Sunday morning (right)
MOGREPS-W ExampleHeavy Rain on 24th October 2011
Good agreement with warning issued by forecaster (below)
3h Rainfall
24h Rainfall
MOGREPS-R p(24h-ppn>50mm)
T+42
MOGREPS-G p(24h-ppn>50mm)
T+48