ENSEMBLE GLOBAL OCEAN WAVE FORECAST SYSTEM

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Status of
ENSEMBLE GLOBAL OCEAN WAVE FORECAST
SYSTEM (EGOWaFS)
For 2nd NAEFS Workshop November 16-18, 2004 H.
S. Chen NCEP/EMC/MMAB
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1. Introduction.

• Meteorological Forecast System (FS ) vs. Ocean
  Wave FS.
• NCEP ocean wave model, NWW3
• Directional, spectral wave model,
• http//polar.ncep.noaa.gov/waves
• - Deterministic FS vs. Ensemble FS.

2. The Ensemble Global Ocean Wave FS (EGOWaFS).
3. Preliminary Results.
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1. Introduction.
Initial Condition
Meteorological FS

• chaotically nonlinear,
• the butterfly effect.

Initial Condition
Sea surface forecast wind
Ocean Wave FS
- weakly nonlinear,
- highly dissipative.
Forecast wave field
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  Figure 1.1 A
schematic illustration of the growth of an
isopleth of the forecast error probability
distribution function, from (a) initial phase,
to (b) linear growth phase, to (c) nonlinear
growth phase, to (d) loss of predictability.
(borrow from ???)
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Remark
The initial wave field has a significant impact
on the forecast waves only up to the first
24 hours and the wind forcing is the most
dominant factor throughout the forecast period.
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2. The Ensemble Global Ocean Wave FS (EGOWaFS).
- 10 ensemble wind fields 1 control wind field
(operational),

- NWW3 wave model,
- 10 ensemble wave fields 1 control wave field
(operational).
- Ensemble parameters Ens Mean, Ens Spread and
Ens Probability.
- Output only up to 84 hour forecast, will
increase in the future.
- In Parallel Run. Hopefully, operational next
spring.
- use a considerable amount of computer resource.
3. Some results for 2004 June.
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Green thin lines ensembles, Red
dash line with sign control, Blue line with
sign ensemble mean Black dot with o
sign observed data.
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Some Remarks
The ensemble FS is more reliable and realistic
than the deterministic FS.
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A long list of works need to be done, such as
verifications, postprocessors, score analysis,
etc.
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