Unified storm tracking

1. Unified storm tracking Ronald Frenette High impact weather lab Québec region Environment Canada CMOS, Montréal May 2012

2. Menu • Storm tracking algorithm • Preprocess • Minima and tropical centers diagnostic • Tracking • Outputs • Applications • Operational • Model verification • Climatology • Impact oriented product

3. Group effort • Rabah Aider • Jean-François Caron • Louis-Philippe Caron • Corina Costea • Ronald Frenette • Stéphane Gagnon • Philippe Gachon • Rares Gheti • Anne-Marie Leduc • Philippe Martin, • Milka Rodojevik • Christian Saad • Mark R Sinclair • Katja Winger • Ayrton Zadra Canadian Meteorological cener Université du Québec à Montréal High impact Lab Québec region Environment Canada

4. Rational - Unifying the code } Several versions of the code Tropical center diagnostic simple tracking method Pressure/Vorticity centers elaborated tracking method Tropical center and transition diagnostic AND Pressure/Vorticity centers Both using same elaborated tracking method One program, one code. Maintenance, implementation easier }

5. Step 1. Preprocessing the data For pressure center tracking 300km Cressman filter to remove small scale details Raw NWP output

6. Step 1. Preprocessing the data For 850 or 500 hPa vorticity tracking 800 km Cressman filter 0.75 x10-5 for 1000 hPa 1.5x10-5 for 500 hPa

7. Step 2a. Identifying minima • Uses cubic splinesbetween grid points for interpolation for a more precise location. • Surface pressure field unreliable over higher terrain: • Filter with vorticy threshold. • Threshold varies with terrain height

8. Step 2b. Identifying tropical centers • Pressure minimum • A 300km Cressman filter is applied to the 850 hPa vorticity field • A vorticity max higher the 2.5x10-5 s-1 is present within 150km of pressure center. • 850-250 hPa thickness higher then 925 dam within 150km. • Indicating the presence of a deep and vertical warm center • A 10m wind speed higher then 22 kts within 225km • A baroclinicity in the low levels • Measured in terms of the asymmetry of the 900-600 hPa thickness*. • Use the Safir-Simpson surface wind thresholds to classify • Tropical Depression : V10m < 34 kts • Tropical Storm : 34 < V10m < 64 kts • Hurricane : V10m > 64 kts *Sinclair, M. R., 2004: Extratropical Transition of Southwest Pacific Tropical Cyclones. Part II: Midlatitude Circulation Characterisitcs, Mon. Wea. Rev., 132, p. 2149.

9. Step 3. Tracking the centers • r(t*) is the position of the first point of the trajectory and r(t) is the position of the current point. • wm is a weight function depending on the number of analysis per day (2,4,8,..) Mark R Sinclair’s method

10. Step 4. Outputs EC – Global EPS Lab Project with Rares Gheti

11. Step 4. Outputs Multi model outputs http://meteocentre.com/tracking/index_e.html From: Jean - François Caron – UK Met

12. Application – operational forecasting • Snow storm/Freezing rain - jan2012 • RaresGheti poster • May 29 – 15:30 - 16:30 - Soprano - 5521 Half of the member tracks shifting more to the north (right solution). Deterministic still with southern track

13. Application - Model Verification • Common domain for regional/global comparison • Track over a forecast period (ex 0-48h) • Variable track buffers (66, 100, 300km) • Compare forecast tracks with analyses same domain/buffer/period • Build a contingency table Probabilistic scores Ex: member 17, 100km buffer 0-48h RaresGheti poster shows results for different system Do the same for all the members then: For each grid point: calculate the percentage of member passing over this grid point

14. Application - Storm impacts study • To improve our knowledge of weather systems affecting urban and surrounding zone • Hudson Bay (MTQ project) and southern Québec • track density, storm duration, mean circulation, mean vorticity and wind 1000 hPa • To analyze the links between storms and hazardous events (extremes, high impact) • 2m temperatures, precipitations and 10m wind • To understand the impact of these extremes on population health and infrastructures. • To predict future changes in the storm climatology and theirs effects on surface extremes • cerca 2050

15. Application – Storm impact forecasting • Storm buffer: • vorticity radially changes sign • Risk zone: • 1979-2011 Climatology of storm positions and characteristics using reanalyses/observations. • Determine pertinent variables and thresholds impacting local infrastructures (wind speed, storm duration and speed of storm, ice, waves,…) • Storm impact risk zone forecast products (vigilance, alert system, multi time scale) vorticity center -Done -Ongoing-Planned

16. Talks, links and articles • CMOS Talks and Posters: • Philippe Gachon: • Extratropical cyclones responsible for storm surge events and coastal erosion processes in the Gulf of St. Lawrence (Québec, Canada): an assessment over the present and future periods • Changes in weather storm events over the Hudson Bay area (Canada) in links with regional sea-ice state • RaresGheti: • On the use of the ensembles by the Quebec Storm Prediction Center in detecting and tracking surface cyclones • Internal link: • http://neige.wul.qc.ec.gc.ca/produits/trajectoires/ • External link: • http://meteocentre.com/tracking/ • Articles: • Sinclair, M. R., 1997: Objective identification of cyclones and their circulation intensity, and climatology. Wea. Forecasting, 12, 595–612 • Sinclair, M. R., 2004: Extratropical Transition of Southwest Pacific Tropical Cyclones. Part II: Midlatitude Circulation Characterisitcs, Mon. Wea. Rev., 132, p. 2149