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Implementation of SWAN at SR SWAN Simulating WAves Nearshore September 2010

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Implementation of SWAN at SR SWAN Simulating WAves Nearshore September 2010

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    1. Implementation of SWAN at SR SWAN = Simulating WAves Nearshore September 2010 Alex Gibbs Pablo Santos WFO Tallahassee WFO Miami Alex.Gibbs@noaa.gov Pablo.Santos@noaa.gov

    2. Outline Background - WAVEWATCH III SWAN Brief Model Description/Review Forcing Winds Boundary Conditions WNA Real-Time Ocean Forecasting System (RTOFS) Gulf Stream Data Running SWAN and recommended general procedures Caveats about Output Examples, Future, and Other Possibilities

    3. Other Recommended Training For maximum benefit, it is recommended you review or complete the following LMS/COMET Modules if not already done: Near Shore Wave Modeling with SWAN Analyzing Ocean Swells Operational Use of WW3 Wave Types and Characteristics Wave Life Cycle I and II

    4. WAVEWATCH III (v3.14)

    5. WAVEWATCH III

    6. Products Available on AWIPS: 2D Multigrids mosaic approach in AWIPS since Build 8.3 30/15 min resolution GlobalWave and WNAwave in AWIPS 10 min resolution - WNAwave10 in AWIPS 4 min resolution WNAwave4 in AWIPS AWIPS wave fields available Significant Wave Height Peak Period and Direction Wind Wave, primary and secondary swells Height, Period, and Direction No Mean field because it does not make physical sense Models forced by GFS winds and GFS/GFDL blend (HWRF in future) for Hurricanes GlobalWave Spectral resolution (freq/dir) 25/24. All other in multigrid will be increased to 50/36 in October 2010. Individual spectral points output will remain 25/24 until at least later in FY11.

    7. GlobalWave vs WNAwave(10,4)

    8. SWAN

    9. SWAN

    10. WFO Miami SWAN Domain

    11. SWAN Wave Processing Flow Chart

    12. SWAN Input vs WNA

    13. Running SWAN with GFE Winds Most forecasters are accustomed to producing their winds forecast with ISC turned on as shown to the right. But as shown in the next transition, SWAN domain is larger than your CWA. If you work with the wind grids with ISC on with no attention to the winds across the entire SWAN domain, you will end up sending highly discontinuous wind grids to SWAN that make no physical sense. Hence, while working on your wind grids, make sure ISC is off as shown in the next transition to the right. Then as a last step turn ISC back on and check for any neighbor inconsistencies that might need attention. If additional changes are made to attain consistency with neighbors care must be taken to make sure discontinuities do not arise when you turn ISC back off to look at the actual winds you will be sending to the SWAN. Most forecasters are accustomed to producing their winds forecast with ISC turned on as shown to the right. But as shown in the next transition, SWAN domain is larger than your CWA. If you work with the wind grids with ISC on with no attention to the winds across the entire SWAN domain, you will end up sending highly discontinuous wind grids to SWAN that make no physical sense. Hence, while working on your wind grids, make sure ISC is off as shown in the next transition to the right. Then as a last step turn ISC back on and check for any neighbor inconsistencies that might need attention. If additional changes are made to attain consistency with neighbors care must be taken to make sure discontinuities do not arise when you turn ISC back off to look at the actual winds you will be sending to the SWAN.

    14. SWAN and WNA Boundary Conditions You will have the option to use NOAA Wave Watch Boundary Conditions. As an example to the right, you have the boundary points of MFL SWAN domain. In general, you will want to use WNA BC most of the time. However, if primary forcing is the Wind (Wind Waves), you are not concerned with swells, and WNA forcing (GFS/GFDL) Winds are in great error you are recommended not to use it in those cases (rare). The Wind forcing from WNA do not have to match exactly the GFE Winds. Remember your SWAN domain extends well beyond your CWA and part of the reason is to allow SWAN to correct input coming from WNA. If swells are a concern, you must use WNA unless WNA is grossly in error. In that case you would likely need to run SWAN w/o WNA and account for Swell manually using the process typically used by your office. Bottom line, you should always examine WNA in D2D prior to running SWAN. You will have the option to use NOAA Wave Watch Boundary Conditions. As an example to the right, you have the boundary points of MFL SWAN domain. In general, you will want to use WNA BC most of the time. However, if primary forcing is the Wind (Wind Waves), you are not concerned with swells, and WNA forcing (GFS/GFDL) Winds are in great error you are recommended not to use it in those cases (rare). The Wind forcing from WNA do not have to match exactly the GFE Winds. Remember your SWAN domain extends well beyond your CWA and part of the reason is to allow SWAN to correct input coming from WNA. If swells are a concern, you must use WNA unless WNA is grossly in error. In that case you would likely need to run SWAN w/o WNA and account for Swell manually using the process typically used by your office. Bottom line, you should always examine WNA in D2D prior to running SWAN.

    15. SWAN and WNA Boundary Conditions

    16. SWAN and WNA Boundary Conditions

    17. SWAN Input Gulf Stream Forecasts

    18. SWAN Input Gulf Stream Forecasts

    19. What do I need to do to Run SWAN? Do your Wind Grids as you normally do with the caveat for area coverage discussed earlier in mind. THE INITIAL TIME OF YOUR WIND GRIDS IS THE STARTING TIME OF YOUR MODEL RUN. Start the wind grids back 12 hours from your current time. A recommended schedule is this: Day Shift/Afternoon Package start winds back at 06Z. Evening Update start winds back at 12Z. Midnight Shift/Morning Package start winds at 18Z previous day. Morning Update start winds at 00Z. Why? Because the model runs in nonstationary mode starting from a state of zero waveheights outside WNA BC. So you want to provide time for the model to spin up. Running the model in nonstationary mode also allows for more realistic wave transitions associated with rapid changes in wind conditions but this is the price one has to pay. In the future options to start the model run with a previous run will be explored. Do your Wind Grids as you normally do with the caveat for area coverage discussed earlier in mind. THE INITIAL TIME OF YOUR WIND GRIDS IS THE STARTING TIME OF YOUR MODEL RUN. Start the wind grids back 12 hours from your current time. A recommended schedule is this: Day Shift/Afternoon Package start winds back at 06Z. Evening Update start winds back at 12Z. Midnight Shift/Morning Package start winds at 18Z previous day. Morning Update start winds at 00Z. Why? Because the model runs in nonstationary mode starting from a state of zero waveheights outside WNA BC. So you want to provide time for the model to spin up. Running the model in nonstationary mode also allows for more realistic wave transitions associated with rapid changes in wind conditions but this is the price one has to pay. In the future options to start the model run with a previous run will be explored.

    20. What do I need to do to Run SWAN? For Example: You are the day shift and you start your winds back to 06Z using RTMA, LAPS, MSAS, or a combination that gives you the best representation of what was observed. If you initiate a run in the afternoon and choose GFS40, the winds the model will use are those from RTMA til 12Z and from 12Z on those from the GFS40 out to however far the 12Z data is in. So make sure the model is completely in. For Example: You are the day shift and you start your winds back to 06Z using RTMA, LAPS, MSAS, or a combination that gives you the best representation of what was observed. If you initiate a run in the afternoon and choose GFS40, the winds the model will use are those from RTMA til 12Z and from 12Z on those from the GFS40 out to however far the 12Z data is in. So make sure the model is completely in.

    21. Running the SWAN For Example: If your run starts at 12Z and the latest Gulfstream forecast available is from 00Z the previous day and out to 144 hours, but you requested a run out to 132 hours, then the length of the run will be scaled back to 108 hours. A text alert would be generated stating this information. If no Gulf stream data is available you will be notified also and the run will proceed w/o it. After the model run ends, you get notified also. If you find out you made a mistake and you need to resubmit a model run, you can do so at any time. For Example: If your run starts at 12Z and the latest Gulfstream forecast available is from 00Z the previous day and out to 144 hours, but you requested a run out to 132 hours, then the length of the run will be scaled back to 108 hours. A text alert would be generated stating this information. If no Gulf stream data is available you will be notified also and the run will proceed w/o it. After the model run ends, you get notified also. If you find out you made a mistake and you need to resubmit a model run, you can do so at any time.

    22. SWAN Output vs WNA

    23. SWAN - Viewing Output/D2D

    24. SWAN Populating Output in GFE

    25. ADDITIONAL COMMENTS REGARDING SWELL POPULATION WITH SWAN

    26. Illustration of Hurricane Earl Swell Event Across Southeast Florida Issues with Partitioning of SWAN Output in GFE

    27. Hurricane Earl Run 20100903_0600Z Upper Left Panel: Hs in Image, significant swell height in white contour, and peak wave direction in yellow arrows. Lower Left Panel: Hs in Image, primary swell height in white contour, and peak wave direction in yellow arrows. Upper Right Panel: In red square is a sequence in z time of Hs (left) and significant swell height (right) for buoys 41009 and 41010. Lower Right Panel: Spectral Density Plot. Lesson: Swan Swell and WNA Primary swell both look all right. However, there are two distinctive peaks in the energy spectra, this means Swan Swell and WNA primary swell will not match even when statistically they are both fine. This would also be the case even if there is one peak in the energy spectra but that peak happens to be broad. This is a case where you if you try to derive WindWaveHeight in the grids from WaveHeight and Swells you will not get the right outcome. You will be assigning higher wave heights to the wind waves that they should have. In that case you should populate WindWaveHeight and Swell with NOAA Wave Watch and run a consistency check to make sure they do not exceed the WaveHeight derived from the Swan. Upper Left Panel: Hs in Image, significant swell height in white contour, and peak wave direction in yellow arrows. Lower Left Panel: Hs in Image, primary swell height in white contour, and peak wave direction in yellow arrows. Upper Right Panel: In red square is a sequence in z time of Hs (left) and significant swell height (right) for buoys 41009 and 41010. Lower Right Panel: Spectral Density Plot. Lesson: Swan Swell and WNA Primary swell both look all right. However, there are two distinctive peaks in the energy spectra, this means Swan Swell and WNA primary swell will not match even when statistically they are both fine. This would also be the case even if there is one peak in the energy spectra but that peak happens to be broad. This is a case where you if you try to derive WindWaveHeight in the grids from WaveHeight and Swells you will not get the right outcome. You will be assigning higher wave heights to the wind waves that they should have. In that case you should populate WindWaveHeight and Swell with NOAA Wave Watch and run a consistency check to make sure they do not exceed the WaveHeight derived from the Swan.

    28. Illustration of Hurricane Danielle Swell Event Across Southeast Florida

    29. Hurricane Danielle Run 20100825_1800Z

    30. Illustration of SWAN Gulf Stream Current Interactions

    31. Eight Test Cases Follow Significant Wave Height (Hs) and Peak Wave Direction are shown in the following slides for the following 8 cases (Each case is a 12 hours forecast valid on 20091003_0000Z for each): Homogeneous North Wind at 15 knots across domain (with and without Gulf Stream) Homogeneous East Wind at 15 knots across domain (with and without Gulf Stream) Homogeneous South Wind at 15 knots across domain (with and without Gulf Stream) Homogeneous West Wind at 15 knots across domain (with and without Gulf Stream) In images that follow blue is Hs < 1ft, light blue 1-2ft, green 2-3ft, yellow 3-4ft, and red/purple > 4 feet.

    32. SWAN Hs/Peak Dir North Wind 15KTS Case

    33. SWAN Hs/Peak Dir East Wind 15KTS Case

    34. SWAN Hs/Peak Dir South Wind 15KTS Case

    35. SWAN Hs/Peak Dir West Wind 15KTS Case

    36. Key West Illustration of Local Mesoscale and Hi-Res Effects

    37. Edited Swan Domain but no mesoscale effects

    38. HI RES Effects

    39. The Future Enabling WNAwave Boundary Conditions in SWAN for all SR offices in near future. Also enable inner nests. In order to more properly account for Swells in the future, upgrade SWAN post processing software. The goal is to decompose into several wave groups (Hs, Tp, Dp, WVH, WVP, WVD, S1H, S1P, S1D, S2H, S2P, S2D, etc). At that time, this training will be updated to adjust our procedures accordingly. Coordinate through SR developing this capability with EML/USACOE. New products - Given our increasing capabilities in this area: More detailed broken down wave information in CWF and newly enhanced marine web based graphics. Also steepness as a safety issue for small craft. Increase spectral resolution of the SWAN.

    40. WFO Miami SWAN Nested Domains

    42. The Future BUT given the current version of SWAN we have at SR, what can we do immediately: Publish SWAN/Grads based graphics. Provide Time series of SWAN Wave parameters for critical locations (mouth of inlets, DWH point, etc). Enhance both zone and point and click versions of CWF with: Dominant Period Information Include additional wave information based on Rayleigh distribution. For example, H1/10 = 1.27*Hs; H1/100 = 1.67*Hs. So what about including in the forecasts wording such as SEAS 4 TO 6 FEET WITH 1 IN 10 WAVES 5 TO 8 FEET or something like that. What about Swells?

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