Enhancing Wind Forecasting for Weather Forecast Offices

1. NDFD Rachel Gross Charlie Paxton Mark Powell

2. 1. Define the problems, impacts and how they affect each WFO • Constrained Velocity In Extended Periods • Coordination • Ready To Use Analysis Grid • Ready To Use TPC Grids • Best Wind Estimate Forecast • Grids Don't Account For Varying Terrain Effects • Mission Impossible • Probabalistic Grids • What If Scenarios?

3. 2. Break down each problem and discuss interests of each WFO in groups; identify common interests • I like to think from the viewpoint of myself as a customer, rather than an NWS meteorologist

4. CONSTRAINED VELOCITY IN EXTENDED PERIODS • -The gridded wind fields drop off farther out in time to address maximum wind speed criteria set by the TPC, but these numbers convey a decrease in storm intensity which needs to be addressed with a different type of grid. RG

5. COORDINATION • -Images from the NDFD wind grids for the 2004 Hurricanes showed inconsistent method of creating, collaborating, and publishing wind grids to NDFD. CP

6. READY TO USE ANALYSIS GRID. • 1) Provide forecast offices with a real time or nearly real time high resolution analysis grid during hurricane situations that we can use with GFE. • I think that HRD's HWIND application provides an excellent starting point for this. • Recently Nicholas Carrasco, from HRD, visited me and we played with the idea of having HRD put their near real time analyzes in a netCDF format grid. • I am willing to work with him to get AWIPS configured to display it. But I think it is a good starting point. • If you couple that idea with Mark's suggestion to couple this with an inland hurricane wind decay model based on persistence, at least for the short range (less than 12 hours time frame), that could make a huge positive impact on the grids and it is worth looking into. PS

7. READY TO USE TPC GRIDS • -High resolution gridded fields need to be provided to the WFO, and incorporated into the GFE, with little or no modification at the WFO level. • During a tropical event, forecasters should be focused on protection of life and property, and not grids. • Especially since there are no defined users of these gridded fields in a tropical event. AD

8. READY TO USE TPC GRIDS • - If there is no skill in producing these gridded forecast fields, then localizing the fields for a CWA accomplishes nothing except maybe to make the grids look prettier. • Bottom line - WFOs should not waste time working on these gridded forecast fields during an event - so need a best guess initial and forecast fields from TPC/HRD (with landfall wind decay included) that can be plugged into the NDFD without modification. • There has been a substantial effort by the TPC and the emergency management community to emphasize the error cone - and TPC is producing probability graphics on their web page - yet we continue to produce deterministic forecast fields in contradiction to these efforts. AD

9. READY TO USE TPC GRIDS • If an experimental H*Wind gridded field were to be provided in a format that can be easily displayed in AWIPS, would that be of help? • We are not involved in wind forecasting at present. However, the poor skill in intensity forecasting makes projecting the current experimental H*Wind field along the official forecast track a persistence forecast; would this type of a experimental  persistence projection that creates a series of gridded "snapshot" fields and takes into account whether you are over land or ocean be of interest? • Upon landfall, the HRD inland decay model could be implemented. Also it may be possible to redefine a contoured wind field such that a given wind speed contour represents a specified probability of exceedance. • For example, a 34 kt wind contour with a 5% probability of exceedance. In that way you have a probabilistic product that might be easier for users to understand. MP

10. BEST WIND ESTIMATE • –.As a customer, I would love to see your best estimate of expected winds, given latest TPC forecast track… PW

11. GRIDS DON'T ACCOUNT FOR VARYING TERRAIN EFFECTS • -For Puerto Rico and the U.S.V.I, the intricacies of the island's topography lead to a much more complicated gridded based forecast. • The grids that are given to the offices right now are much too simplistic and do not take into account the track deviations which could make such substantial differences to local winds across the islands. • I know this may not come into play for other offices and therefore may be overlooked by some. • I am very much in favor of a probabalistic approach or product to account for such deviations. RG

12. GRIDS DON'T ACCOUNT FOR VARYING TERRAIN EFFECTS • This is a very important issue that is also relevant to Hawaii. I know of some numerical modeling studies that have suggested that mountainous islands could deflect a storm track and this certainly happens for storms that affect Taiwan. • Frank Marks mentioned that Hugo and Georges showed some evidence of track deviations around the island  Are the track deviations you mention ever apparent in the various model guidance available to you as well as the official forecast? • There is some research going on regarding techniques to account for complex terrain that could possibly be applied to gridded wind fields for Puerto Rico and the Virgin Islands.  • If any probabilistic or deterministic approach were to be successful, I think they would both need to account for the topography.MP

13. MISSION IMPOSSIBLE • - Is producing deterministic gridded forecast fields an impossible mission? Is there anything in the literature that would suggest this is possible? If there is no skill in these forecasts, then what do we transition to that will be meaningful and useful to the customer? AD

14. PROBABALISTIC • NDFD grids show deterministic values. Deterministic wind grid values produce a focus on the exact track forecast and don’t convey the uncertainty. CP

15. PROBABALISTIC • The gridded fields involving tropical systems should be probabilistic - or there should be some type of guidance/research on the performance of forecast deterministic wind fields in proximity of tropical systems (how good is good?). AD

16. PROBABALISTIC • Develop probabilistic wind grids to complement the deterministic wind grids and for use in our routine TEXT products. • Along those lines I have worked with Rich and Dave Sharp doing some development work. In fact, we have our AWIPS configured and experimenting with the cumulative probabilistic wind grids. • However this still does not provide everything we need because from the probabilistic wind grids you can only calculate incremental probabilities. • Those only mean the chance of the onset for a given wind speed threshold during a particular 12 hour period. • For our text products, we need the actual probability of any given event (wind exceeding tropical storm or hurricane conditions) occurring during the regular text products forecast periods. PS

17. PROBABALISTIC • Yesterday we had a meeting here with Mark DeMaria. Mark agreed to create experimental grids using a couple of last year storms that contain interval specific probability information that gives the chance of any given conditions during a specific 12 hours period. • The idea is for us to experiment with the grids in IFPS and look into ways to use this information in our text products. I think HRD can help us out figure out a smart way of using probability information in the grids and the text products. • We need to develop over time a concept that we can present in a forum like the NOAA hurricane conference. Our ultimate goal on this should be to influence policy so that this can become operational. PS

18. PROBABALISTIC • Certainly think probabilistic is the way to go. Take last year's Charley as an example. • Did customers have specific information on range/probability of conditions at a given location given a variety of possible scenarios that fall within the average rate of forecast error in TPC forecasts? PW

19. PROBABALISTIC • Have had little time to think about this and discuss with others, so hope I'm making some sense. • Probably would be best to have a TPC/HRD baseline gridded wind field based on TPC forecast, but I believe the WFO can add some probabilistic value to these forecasts. • Would be worth brainstorming this, and how we can transform from deterministic to probabilistic, stepping outside the box as needed to find solutions to make it a reality. PW

20. PROBABALISTIC • -Deterministic wind grids should not be produced to show exact speed and direction past the first couple of periods to stay in line with TPC requirements. RG

21. WHAT IF? • …along with the ability to modify the wind forecast by modifying the TPC forecast.  • For example, with TPC forecast track, I get a given forecast of surface winds.  • With a 10 degree deviation to the west, I would get an adjusted forecast, with a 10 knot deceleration, I get a different adjustment, etc.  • That way, when (I meant "if", of course) the storm starts to deviate from forecast track, I have immediate access to guidance on what the deviation may mean to surface winds in my area.  • From the various forecasts (TPC track, deviation to left, deviation to right, decceleration, acceleration, etc etc), a probability value for a certain level wind gust (say, 70kts needed for damage to my house, for example) could be derived.  • For Emergency Managers, knowledge of the range and probabilities of potential conditions may help this with their "risk management" decision-making. PW

22. WHAT IF? • We have some MM5 runs done at UM that show these deviations nicely, particularly Georges. FM

23. WHAT IF? • Very interesting ideas. If the regionally dependent forecast forecast error statistics are available, it seems like one could perturb the forecast track in different ways to allow one to visualize different landfall scenarios. • In addition, perhaps ensemble forecasts could provide some guidance and possible scenarios by viewing the members showing the distribution of possible landfall points. • Sim Aberson of HRD is an expert in this area and may have some ideas on how HRD might contribute to investigating these ideas. MP

24. WHAT IF? • I think an ensemble-like approach could be beneficial. • Important to keep in mind the variety of customers we have...many plan based on the most-likely scenario, while others plan based on the worst-case scenario, still others plan/act once a scenario is expected to reach a certain plateau (and would want to know the probability that that plateau will be reached, e.g. winds or waves above a certain threshold). • Ensemble would allow us to better express the uncertainty that exists in a given forecast. • As technology continues its rapid advance (and we continue trying to keep up), this may become (or may already be) possible. • We could provide the necessary information to all of our customers, not just those relying on the most-likely scenario.PW

25. 3. Set performance standards as a basis for success

26. 4. Generate alternatives and new ideas (timed brainstorming) for solving the problem • I like to think from the viewpoint of myself as a customer, rather than an NWS meteorologist

27. 5. Discuss pros/cons and reach consensus on solving the problem

28. 6. Write up the solution;