Seasonal Forecast for Summer 2013 for Hong Kong 9 Apr 2013, FOCRAII, Beijing H W Tong Hong Kong Observatory
Seasonal Forecast at HKO Temperature and rainfall Most (or two most) likely category No. of TC entering the 500 km range of Hong Kong (for internal use only)
Verification- JJA 2012 Actual Forecast Temp. Above Normal Normal to above normal Rainfall Below normal Normal to above normal X
However, Aug 2012 was expectedly dry Review of 2012 JJA forecast Temperature (C) Rainfall (mm) Obs. Normal Range (81-10) Jun 12 28.1 27.6-28.2 261.5 315-597 Jul 12 28.8 28.6-29.0 467.8 262-490 Aug 12 29.5 28.3-28.8 127.0 301-564 JJA 12 28.3-28.6 856.3 1021-1509 Jun 2012 was well forecast However, Aug 2012 was expectedly dry
August 2012
Aug 2012 – CFSv2 & JMA-CGCM vs actual MSLP
Methodology El Niño/La Nina consideration Large-scale circulation pattern forecast by major centers (CFSv2, JMA-CGCM, ECMWF) Forecasts from major centers Statistical downscaling (from NCEP CFSv2) Simple regression Principle component regression
ENSO Status Neutral in JJA
Large-scale circulation pattern
500Z (upper) & MSLP (lower) Jun 2013 NCEP JMA ECMWF (non-normalized)
850 Wind (upper) & Temp (lower) Jun 2013 NCEP JMA ECMWF (non-normalized)
500Z (upper) & MSLP (lower) Jul 2013 NCEP JMA ECMWF (non-normalized)
850 Wind (upper) & Temp (lower) Jul 2013 NCEP JMA ECMWF (non-normalized)
500Z (upper) & MSLP (lower) Aug 2013 NCEP JMA ECMWF (non-normalized)
850 Wind (upper) & Temp (lower) Aug 2013 NCEP JMA ECMWF (non-normalized)
Above normal temperature ? Short summary Jun Jul Aug NCEP NE’lies Low over E of Luzon Low over NE Luzon W’lies Low over Eastern China JMA E’lies Low over Luzon Ridge E’ies Trough over central SCS EC Above normal temperature ? Below normal rainfall ?
Statistical downscaling Temp. Normal SD Mean pB pN pA Jun 27.9 28.1 0.13 0.46 0.41 Jul 28.8 0.25 0.44 0.31 Aug 28.6 28.7 0.22 0.38 0.40 JJA 28.4 0.34 0.53 Normal to warm Rainfall Normal SD Mean pB pN pA Jun 456 354 0.49 0.41 0.10 Jul 376 320 0.45 0.14 Aug 432 388 0.39 0.43 0.18 JJA 1265 1198 0.29 0.56 0.15 Normal to dry
JJA temperature forecasts from major centers Normal to above normal
JJA rainfall forecasts from major centers Normal to dry 19
Number of tropical cyclones entering the 500 km range of Hong Kong HK
Normal 21
Statistical downscaling Normal SD mean No. of TC in JJA 3.2 2.7 2-3 TC in JJA, near normal
Preliminary summer forecast for Hong Kong 2013 Temperature Normal to above normal Rainfall Normal to below normal No. of TC entering 500 km of Hong Kong 2-3
Thanks
ECMWF http://www.ecmwf.int/products/forecasts/d/charts/seasonal/forecast/seasonal_range_forecast/group/seasonal_charts_rain!rain!1%20month!East%20Asia!201205!tercile%20summary!/ 25
No of TC in El Nino/La Nina/Neutral years