HEFS workshop, 03/12/2015 - National Weather Service · 2015. 3. 10. · Office of Hydrologic...
Transcript of HEFS workshop, 03/12/2015 - National Weather Service · 2015. 3. 10. · Office of Hydrologic...
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.1
James Brown
Seminar E: review results from
Exercise 4
HEFS workshop, 03/12/2015
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.2
Exercise 4: Q1 (BLKO2)
Q1: Are the MEFP-GEFS forecasts more skilful than climatology?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.3
Exercise 4: Q1 (BLKO2) answer
Q1: Are the MEFP-GEFS forecasts more skilful than climatology?
A1: In general, substantially so at moderate lead times and higher flows
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.4
Exercise 4: Q2 (BLKO2)
Q2: Why does the skill increase rapidly from 42-66 hours then decline?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.5
Exercise 4: Q2 (BLKO2) answer
Q2: Why does the skill increase rapidly from 42-66 hours then decline?
A2: Early lead times driven by persistent model states (also in reference)
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.6
Exercise 4: Q3 (FTSC1)
Q3: Are the forecasts more skillful at higher or lower flows? Why?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.7
Exercise 4: Q3 (FTSC1) answer
Q3: Are the forecasts more skillful at higher or lower flows? Why?
A3: High. Good forcing & hydro calibration, plus climatology lacks skill.
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.8
Exercise 4: Q4 (BLKO2)
Q4: Focusing on “all data” (red), are the forecasts broadly reliable? How?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.9
Exercise 4: Q4 (BLKO2) answer
Q4: Focusing on “all data” (red), are the forecasts broadly reliable? How?
A4: Not really. Too many observations fall at high and low ends of forecast
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.10
Exercise 4: Q5 (BLKO2)
Q5: What might explain the “U-shape”?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.11
Exercise 4: Q5 (BLKO2) answer
Q5: What might explain the “U-shape”?
A5: This is classic behavior indicative of lack of spread (over-confidence)
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.12
Exercise 4: Q6 (FTSC1)
Q6: What might explain the tendency for higher frequencies in upper tail?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.13
Exercise 4: Q6 (FTSC1) answer
Q6: What might explain the tendency for higher frequencies in upper tail?
A6: Two things. Lack of spread (both tails) and a conditional bias (too low)
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.14
Exercise 4: Q7 (FTSC1)
Q7: Can the forecasts discriminate occurrences from non-occurrences?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.15
Exercise 4: Q7 (FTSC1) answer
Q7: Can the forecasts discriminate occurrences from non-occurrences?
A7: Yes, much better than climatology. PoD much higher than PoFD.
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.16
Exercise 4: Q8 (FTSC1)
Q8: Decision maker: accept 5% PoFD for flows > 19,932 CFS. What PoD?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.17
Exercise 4: Q8 (FTSC1) answer
Q8: Decision maker: accept 5% PoFD for flows > 19,932 CFS. What PoD?
A8: About 90%, i.e. when event occurred, warnings were correct ~90%
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.18
Additional questions
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.19
Exercise 4: Q9 (FTSC1)
Q9: Compare with histogram before EnsPost (SE.13). More reliable after?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.20
Exercise 4: Q9 (FTSC1) answer
Q9: Compare with histogram before EnsPost (SE.13). More reliable after?
A9: Yes, for “all data”, the EnsPost substantially increases reliability
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.21
Exercise 4: Q10 (BLKO2)
Q10: To what extent has EnsPost increased skill of raw forecasts?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.22
Exercise 4: Q10 (BLKO2) answer
Q10: To what extent has EnsPost increased skill of raw forecasts?
A10: Notably, for low/moderate flows. Not for high flows after ~72 hours.
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.23
Exercise 4: Q11 (BLKO2)
Q11: Why would EnsPost perform better at early lead times?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.24
Exercise 4: Q11 (BLKO2) answer
Q11: Why would EnsPost perform better at early lead times?
A11: Because EnsPost uses prior observation as a predictor (~Adjust-Q).
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.25
Exercise 4: Q12 (FTSC1)
Q12: To what extent has EnsPost increased skill of raw forecasts?
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Office of Hydrologic Development
Silver Spring, MD
National Oceanic and Atmospheric Administration’s
National Weather Service SE.26
Exercise 4: Q12 (FTSC1) answer
Q12: To what extent has EnsPost increased skill of raw forecasts?
A12: As with BLKO2, notably, except for high flows at long lead times.