MJO and the Record-Breaking East Coast Snowstorms in 2009/2010Ja-Yeon Moon1, Bin Wang1, and Kyung-Ja Ha2

1IPRC, 2Pusan National University

Intraseasonal anomalies of (a) OLR (shading) and 200hPa GPH (geopotential height, contour), (b) Surface air temperature (SAT) and 850hPa GPH, and (c) time series of area-averaged intraseaonal anomalies of OLR over “A”, “B”, and daily snowfall amount (inches) averaged over eastern US (“C”) from 1 December 2009 to 28 February 2010.

The eastern United States saw several record-breaking snowfall events in the 2009/10 winter. They can be traced to the central and eastern Pacific, which experienced unusually large swings in OLR and remarkable wet-dry-wet cycles from late December to mid-February. Whenever the MJO convection reached the central Pacific, a teleconnection pattern extended to North America, resulting in a westward-tilted deep anomalous trough anchored over the eastern US, producing a low-level pressure dipole anomaly with an anticyclone (cyclone) centered at the US west (east) coast. The warm moist air from the tropics, mixed with the cold air from high-latitudes, resulted in favorable conditions for extremely heavy snowfall.

(a) OLR(Jan 31~Feb 7, 2010), GPH200 (+4days)(b) SAT, GPH850 (+4days)

C

B

A

(c) OLR(A, B), Snowfall(C)

1DEC 6 11 16 21 26 1JAN 6 11 16 21 26 1FEB 6 11 16 21 26 2009 2010