Emerging Powerful MJO Episode in 8-14 Day Period
Causes the warmer East U.S. medium-range forecast
Wet pattern Australia – hopefully in right spot to ease fires
Madden Julian oscillation ALERT: Part of the inspiration for the warmer U.S. forecasts the past few days (Fig. 1) is emergence of an increasingly intense Madden Julian oscillation phase_5 forecast valid in the 8-14 day period (Fig. 2). The intensity forecast of this event by all operational models is increasing and approaching dramatic levels. Many implications beyond the U.S. warm-up are indicated. Most important is the increase in tropical convection north of Australia leading to heavy rains in Indonesia and increased risk of tropical cyclone activity. The wet weather frequently shifts south to affect Australia where rainfall is desperately needed. The strong convection in the tropical West Pacific implies strong subsidence downstream in the tropical Atlantic basin. Implications are a drier and hotter climate for South America centered mostly on Brazil.
Operational models certainly identify a wetter pattern ahead for Australia. However, consensus points toward a wet bias for the western half of Australia while the eastern areas stay parched (Fig. 3). The South America precipitation forecast over the next 15 days is best represented by the Canadian Ensemble indicating dryness except far Northeast and Southeast Brazil (Fig. 4). Brazil is also trending hotter compared to normal.
Fig. 1-2: The GFS ENS biased correction 15-day temperature anomaly forecast (left) and the 15-day MJO forecast by all lead operational models indicates a robust MJO phase_5 (West Pacific tropics) developing in 8-14 days (right).
Fig. 3-4: The 15-day percent of normal rainfall forecast across Australia and South America.