Fleet Weather Center Norfolk

Transcription

1 Fleet Weather Center Norfolk Assessing the value of ensemble guidance for FWC-Norfolk forecasters Presented to the NUOPC Users Workshop LT Rich Rainer N5 Department Head This briefing is UNCLASSIFIED / FOUO June 2011 Forecast Team AGC Brown AG1 Cummings AG2 Nelson AG2 Didier AG3 Dietrich AGAN Gagle

2 AGENDA Objectives Challenge Description of experiment General results Data collection Objective results Subjective findings Possible next steps 2

3 Objectives In an environment where resources are scarce and billets are being reduced to optimal manning levels How do we maintain forecast quality? How to we increase forecaster efficiency (reduce the amount of time necessary to make quality forecasts)? 3

4 Challenge Fleet Weather Center forecasters have a heavy workload 2 forecasters 2 techs Forecasts for 18 OPAREAS Forecasts for ships Wind and seas warnings for the North Atlantic Mediterranean Black Sea South Atlantic 4

5 Description of experiment SGOT shadow forecast team Two forecasters, two assistant forecasters March 15, 2011 through May 15, 2011 FOXX1 plus North Atlantic high winds and seas In addition to traditional guidance products, use NOGAPS ensemble guidance in MetCast/JMV Mean/spread plots Probability of exceedance for winds (35kts) and seas (12 and 18 ) Compete with official forecasts from Watch Floor Develop best practices for use of ensemble guidance Chose to use ensemble as primary source of guidance Validate using satellite, ship, and buoy observations 5

6 OPAREA Forecasts FOXX01 VACAPES WEAX Parameters - Winds and - Seas - Direction - Speed - Height 6

7 Example OPAREA forecast UNCLASSIFIED FOXX01 KNGU MSGID/GENADMIN/FLEWEACEN NORFOLK VA// SUBJ/VACAPES/CHERRY PT/CHARLESTON/JACKSONVILLE/ PORT CANAVERAL/TONGUE OF THE OCEAN OPAREAS FORECAST// POC/COMMAND DUTY OFFICER/-/FLEWEACEN NORFOLK/LOC:NORFOLK VA// TEL: /SECTEL:-0963/ CDO.FWC.NRFK.FCT(AT)NAVY.MIL// RMKS/1.HIGH PRESSURE RIDGES IN FROM THE MIDWEST PRODUCING PARTLY CLOUDY SKIES, MODERATE WINDS AND SEAS THROUGHOUT THE AREA. EXPECT WINDS AND SEAS TO DECREASE AS THIS HIGH PRESSURE TRANSITS SOUTHEAST TONIGHT THROUGH FRIDAY AFTERNOON. 2. VACAPES OPAREA 24 HOUR FORECAST COMMENCING Z. SKY, WEATHER: PARTLY CLOUDY. B. VSBY (NM): 7. C. SURFACE WIND (KTS):NORTHWEST 20 TO 25 GUST 30, DECREASING 13 TO 18 GUST 23 BY 05/18Z. D. COMBINED SEAS (FT):COASTAL:NORTHERLY 3 TO 5. SEAWARD:SOUTHERLY NORTHERLY 5 TO 7. E. MAX/MIN TEMPS (F): 68/52. F. SST(F/C): COASTAL: 55/13. VICINITY OF GULF STREAM: 74/22. G. OUTLOOK TO 48 HOURS: WINDS: NORTHWEST 13 TO 18 GUST 23, DECREASING 10 TO 15 GUST 20 BY 06/06Z, BACKING WEST-NORTHWEST BY 06/12Z, BECOMING WEST 5 TO 10 BY 06/18Z. SEAS:COASTAL:NORTHERLY 3 TO 5, ABATING 2 TO 4 BY 06/06Z. SEAWARD: NORTHERLY 5 TO 7, ABATING 4 TO 6 BY 06/18Z. 3.CHERRY PT OPAREA 24 HOUR FORECAST COMMENCING Z. A. SKY, WEATHER: PARTLY CLOUDY. B. VSBY (NM): 7. C. SURFACE WIND (KTS): NORTHWEST 18 TO 23 GUST 28, DECREASING 15 TO 20 BY 05/06Z, DECREASING 13 TO 18 BY 05/18Z. COMBINED SEAS (FT):COASTAL: NORTH 2 TO 4. SEAWARD:NORTH 5 TO 7, ABATING 4 TO 6 BY 05/18Z. E. MAX/MIN TEMPS (F): 72/54. F. SST(F/C): COASTAL: 56/13. VICINITY OF GULF STREAM: 72/22. G. OUTLOOK TO 48 HOURS: WINDS:NORTHWEST 13 TO 18, DECREASING 8 TO 13 BY 06/06Z, BECOMING WEST 5 TO 10 BY 06/12Z, BACKING SOUTHWEST BY 06/18Z. SEAS:COASTAL: NORTH 2 TO 4, BECOMING CONFUSED BY 06/12Z. SEAWARD: NORTH 4 TO 6, BECOMING NORTHWEST 3 TO 5, BY 06/12Z. 4. CHARLESTON OPAREA 24 HOUR FORECAST COMMENCING Z. A. SKY, WEATHER: PARTLY CLOUDY. B. VSBY (NM): 7. C. SURFACE WIND (KTS):NORTHWEST 15 TO 20, BECOMING NORTH 10 TO 15 BY 05/18Z. 7

8 OPAREA validation C. SURFACE WIND (KTS):NORTHWEST 20 TO 25 GUST 30, DECREASING 13 TO 18 GUST 23 BY 05/18Z. D. COMBINED SEAS (FT):COASTAL:NORTHERLY 3 TO 5. Collect all available observations in OPAREA Compute average observation value Calculate distance outside of forecast range Example: Average observation was 7ft seas, forecast error was +2ft. 8

9 Example wind and seas warning HIGHLIGHTED CONTOURS: WINDS >35KTS & >50KTS; SEAS >12FT & >18FT SGOT Shadow in Black Watch Floor in Yellow 9

10 General results VACAPES forecasts made with the help of ensemble guidance outperformed official VACAPES forecasts No quantitative assessment of high winds and seas forecasts (yet), but sense is that they are comparable and quicker to generate Uncertainty information is welcome, but slows down the forecast process when large uncertainty is present Need for products that clarify the form of the uncertainty and the reason for the uncertainty 10

11 Data collection 11

12 Objective results (24hr-48hr) VACAPES wind direction Bias RMSE % outside threshold Prob. guidance 48.7deg 16.3 (39) Det. guidance 57.1deg 23.8 (57) Percent improvement 14.8% 31.6% VACAPES wind speed Bias RMSE % outside threshold Prob. guidance 2.3kts 4.6kts 6.9 (16) Det. guidance 3.1kts 5.4kts 10.8 (25) Percent improvement 25% 13.8% 36% VACAPES wave height Bias RMSE % outside threshold Prob. guidance -0.02ft 0.57ft 0.42 (1) Det. guidance 0.25ft 1.06ft 7.59 (18) Percent improvement 93.3% 46.7% 94.4% 12

13 Objective results (48hr-72hr) VACAPES wind direction Bias RMSE % outside threshold Prob. guidance 54.4deg 24.1 (54) Det. guidance 61.2deg 26.3 (59) Percent improvement 11.2% 8.5% VACAPES wind speed Bias RMSE % outside threshold Prob. guidance 2.0kts 4.9kts 8.9 (20) Det. guidance 2.6kts 4.9kts 9.4 (21) Percent improvement 21% 1% 4.8% VACAPES wave height Bias RMSE % outside threshold Prob. guidance ft 0.64ft 1.5 (3) Det. guidance 0.33ft 1.5ft 4.6 (14) Percent improvement 98.7% 48.4% 68.2% 13

14 Direction error (deg) 24hr wind direction errors 200 Wind direction, 24hr forecast error (deg) Shadow Watch Floor

15 RMSE (deg) Exceedance (%) Wind direction errors Wind direction RMSE (deg) Shadow Watch Floor Wind direction threshold exceedance (%) Shadow Watch Floor

16 Speed error (kts) 24hr wind speed errors 16 Wind speed, 24hr forecast error (kts) Shadow Watch Floor

17 RMSE (kts) Exceedance (%) Bias (kts) Wind speed errors Wind speed RMSE (kts) Wind speed bias (kts) Shadow Watch Floor Shadow Watch Floor Wind speed threshold exceedance (%) Shadow Watch Floor

18 Height error (ft) 24hr wave height forecast errors 3 Wave height, 24hr forecast error (ft) Shadow Watch floor

19 RMSE (ft) Percent exceeded Bias (ft) Wave height forecast errors Wave height RMSE (ft) Wave height bias (ft) Shadow Watch Floor Shadow Watch Floor Wave height threshold exceedance (%) Shadow Watch Floor

20 Subjective wind/sea warnings findings Shadow wind and seas warnings seem comparable to Watch Floor products. Data exists for objective validation Shadow wind and seas production was faster. 20

21 Utility of ensemble guidance Used ensemble as primary source of guidance. Used deterministic to validate. Not obviously best way forward Ensemble is great when uncertainty is low (typically associated with high pressure). Ensemble slows the forecast process when uncertainty is high (especially for fast moving and deep low pressure systems). Found it useful to apply color bar lower thresholds to cut down on overwhelming data. 21

22 Needs Ensembles raise questions. We need new products to tell us why the uncertainty looks the way it does Sensitivity products Need quick, detailed information about form of uncertainty. E.g. plumes, skewness. Guidance on how to define relevant uncertainty thresholds. Uncertainty parameters that support all relevant mission areas. 22

23 Personal takeaways How I would use this on the watch floor tomorrow: Probability products for winds and seas Use deterministic models as primary form of guidance and ensemble as means of identifying where additional attention is necessary But Really want information about the form of the uncertainty and information about why the uncertainty is there 23

24 Possible next steps NPS thesis topics Validate winds/seas Conditional verification Compare with objective guidance Automated winds and seas warnings Possible additional experiments Alter CONOPS so that deterministic model is primary source of guidance and use ensemble secondarily Inclusion of GFS ensemble Experiment with products that communicate form of uncertainty and sensitivity information Write 120hr forecast products 24