The Downstream Influence of Organized Tropical Convection Tropical

The Downstream Influence of Organized Tropical Convection, Tropical Cyclones, and the Extratropical Transition of Tropical Cyclones over the Western Pacific Patrick Harr Naval Postgraduate School L H L Nitta, JMSJ, 1987 Horel and Wallace, Monthly Weather Review, 1981.

Theme: Impacts as a Function of Scale and Season Global scale, slowly varying (intraseasonal) Madden-Julian Oscillation (MJO) seasonal: higher amplitude during northern winter and transition seasons Regional scale (seasonal, intraseasonal) Monsoon systems, equatorial waves seasonal: transition seasons summer hemisphere Synoptic Scale Equatorial waves, tropical cyclones, extratropical transition events seasonal: summer, transition seasons

Issues of Scale and Season • Madden-Julian Oscillation (Madden and Julian 1994, MJO) – Seasonal variability such that the strongest signal occurs during the Northern Hemisphere Winter. – Impacts due Rossby-wave response to regions of anomalous increased and decreased convection (divergent flow). • Heavy Precipitation events over western North America (Reynolds 2005) • “Pineapple Express” • Northern Summer impacts on tropical cyclones (especially in the eastern North Pacific (Maloney and Hartmann 2001) • Northern Summer impact on the North American Monsoon (Higgins and Shi 2001, Mo 2000). http: //www. cpc. ncep. noaa. gov

Impacts during the winter of 2005: Southern California Rain Event http: //www. wrh. noaa. gov/cnrfc

Feb 10 -20, 2005 OLR anomalies http: //www. cdc. noaa. gov http: //www. bom. gov. au/bmrc/clfor/cfstaff/matw/maproom/OLR_modes

FEB 10 -20, 2005 200 h. Pa Velocity Potential Anomalies 200 h. Pa height Anomalies http: //www. cdc. noaa. gov 200 h. Pa Zonal Wind Anomalies Combination of events that lead to a circulation pattern that resulted in a deep trough over the eastern North Pacific

Feb 10 -20, 2005 OLR anomalies http: //www. cdc. noaa. gov Enhanced convection over the central Pacific, which was associated with the eastward extension of the MJO and Rossby response toward North America, was also related to a major outbreak of tropical cyclone activity. Cyclone Meena 03 -07 Feb 2005 Cyclone Olaf 13 -20 Feb 2005 Cyclone Nancy 13 -16 Feb 2005 http: //weather. unisys. com/hurricane

PREDICTABILITY IMPACTS GFS 500 h. Pa Height Standard Deviation Where can THORPEX help? • Role(s) of existing and proposed observations for (measure of forecast difficulty, confidence, definition of initial conditions. projected skill? ) -data assimilation issues +120 h -special observations (i. e. , satellite observations) • phasing with midlatitudes • Sensitivities to initial conditions and their propagation throughout the forecast cycle Increase in a • “plume” of high standard Capitalize on the low-frequency variability of the MJO deviation over the eastern North Pacific that is associated with the large-scale wave train. Reduced standard deviations exist over the Eastern +120 h Hemisphere

Other, smaller-scale factors such as equatorial Rossby waves can also cause farreaching impacts during seasons when the MJO may be non-existent. 2002 2001 Although the MJO has farreaching impacts, it exhibits a large amount of temporal and spatial variability. http: //www. bom. gov. au/bmrc/clfor/cfstaff/matw/maproom/OLR_modes

Regional influences during the northern Summer season • Western North Pacific Monsoon/ Mei-yu: – Teleconnection with precipitation over the northern plains of North America (i. e. , Wang et al. 2001, Lau and Weng 2000, Nitta 1987) (Wang et al. 2001)

OLR Anomalies Minnesota state area averaged precipitation anomalies Oct June http: //www. cdc. noaa. gov 200 h. Pa Height Anomalies http: //www. cdc. noaa. gov/cgibin/Timeseries/timeseries 1. pl 2002

Minnesota Flood: 9 -11 June 2002 From Dave Parsons

Wisc. /Chi. flood event associated with the previous wave packet Mei-Yu convection Wisc/Chi. flood Mn flood

Pacific-Japan Teleconnection Patterns (Nitta 1987, Murakami and Matsumoto 1994, Wakabayashi and Kawamura 2004) • • • Associated with the western North Pacific summer monsoon Also associated with anomalous sea-surface temperatures over the Philippine Sea. Impact summer pattern over Japan a) JJA b) June c) July d) Aug Wakabayashi and Kawamura (2004) Regression maps of the 500 h. Pa streamfunction with the Pacific. Japan pattern for (a) June. August period, (b) June, (c), July, and (d) August

IMPACTS OF EXTRATROPICAL TRANSITION EVENTS: TY Tokage, October 2004, Damage in Japan and to U. S. Navy ships in Japan.

http: //oregonstate. edu/~readw/Octob er 1962. html

0000 UTC 10 Oct 62 TY Emma TY Freda http: //agora. ex. nii. ac. jp/digital-typhoon/ http: //www. cdc. noaa. gov Emma Ex-Freda 250 h. Pa height anomaly 9 -13 Oct 1962 Large-scale wave train associated with the digging trough behind the extratropical transition of Emma and building ridge ahead of the extratropical transition of Emma contributed to the trough over the eastern North Pacific and the movement of the ex-Freda cyclone into the Pacific Northwest.

Impacts on Forecasting The movement of a tropical cyclone into the midlatitudes often induces a large downstream Rossby-wave like response. These large-amplitude circulation features are often mis-positioned, which contributes to errors in the forecast timing and interaction between the decaying tropical cyclone and the midlatitude circulation into which it is moving. Maemi Isabel Maemi Fabian Source: NCEP/EMC model verification web page Isabel Newsweek, 03 July 2000

Impacts on Predictability A “plume” of increased std. dev. propagates downstream of. Where the can THORPEX help? extratropical transition forecast • Periodoccur of enhanced observations and impact position. Local maxima TY Tokage assessment that concentrates on the warm-season, in the base of each successive warm pool region trough of the ET-induced wave to include the western North Pacific monsoon, TCs, ET. train. Largest variability exists ETand Time over North America. -phasing with the midlatitudes -data assimilation impacts Application to teleconnection-based high-impact weather events via OSSEs, etc. • Sensitivities to initial conditions and their propagation throughout the forecast cycle • Capitalize on the components of low-frequency variability TY Tokage http: //agora. ex. nii. ac. jp/digital-typhoon/

Predictability Issues • There is little skill in predicting the onset of a MJO event – If it is recognized that an MJO event is present, then the predictability issue revolves around the response to the anomalous tropical conditions • • Strength of response Persistence of response Phasing of response with midlatitude waves Downstream extent of the response • Many monsoon variations occur at time scales that are longer than the synoptic time scale. Can this lowfrequency variability be utilized to increase predictability associated with warm season precipitation? • There is a need to reduce the variability associated with the downstream response to the extratropical transition of tropical cyclones.