MARCH 2013 30-DAY OUTLOOK
332 PM EST Thu. Feb. 281, 2013
Atmospheric patterns, 700 MB and 500 MB height anomalies, statistical data, and various models such as the ECMWF monthly, NMME, IMME and the CFSv2, along with observed cases from past such months, data from 1895-2000 were used in this forecast.
Sea surface temperature anomalies across the equatorial Pacific remain slightly below normal, and relatively unchanged, with the latest weekly Nino 3.4 anomaly at -0.3c. The MJO has been active during late January and the early February. Current model forecasts for the next 2 weeks, however, indicate a decline in strength of the oscillation. Global sea surface temperature anomaly patterns reflect the negative phase of the PDO, including a large region of warm anomalies in the central north Pacific Ocean with negative sea surface temperature anomalies in the extra-tropics to its west, north and east and southeast, including weak negative anomalies in the eastern equatorial Pacific.

The NAO is negative and is forecast to remain negative through day 14. The PNA index is positive and is forecast to trend negative by day 14.

The MJO remained active over the past week with the enhanced convective phase crossing the Indian Ocean and enhanced convection is becoming better organized on a large scale over the Maritime continent. A strong atmospheric Kelvin wave crossed the Indian Ocean and the Maritime continent in recent days and has contributed to the increase in convection in this area and has effectively resulted in quick propagation of the MJO to the western Maritime continent. Enhanced convection was observed during the past week across the western Pacific and Indian Ocean, primarily north of the equator. Suppressed convection was strong over portions of the southwest Pacific and parts of Brazil. Suppressed phases of the Kelvin Wave and an equatorial Rossby wave generally resulted in mixed convection over the Indian Ocean.

Dynamical model forecast some gradual eastward propagation of the MJO during the upcoming week with the enhanced convective phase centering across the Maritime continent. The models, however, also show a considerable reduction in amplitude throughout the period and stop eastward propagation by Week-2. Influence from other types of sub-seasonal tropical variability are likely contributing to the behavior seen in the forecasts like the Kelvin Wave and westward moving Rossby wave and it is too soon to say that the MJO is weakening over the longer term. The official forecast favors a continuation of a slowly evolving MJO signal over the Maritime continent during the period.

The ensembles are in good agreement on the expected 500-hpa height pattern across North America for March. A ridge is forecast over the western U.S. and Alaska. A trough is forecast over the central and eastern U.S.

Above normal temperatures are forecast for the West coast, the central Great Basin and the southern Rockies. The probability of above normal temperatures is 55 percent. Below normal temperatures are forecast for the Ohio Valley, the mid-Atlantic and the Northeast. The probability of below normal temperatures for this region is 55 percent. The spatial anomalies are in agreement with these anomalies. The remainder of the nation is not expected to exceed climatological values.

Below normal precipitation is forecast for the West coast, the central and northern Great Basin and the northern Rockies. The probability of below normal precipitation across this area is 57 percent. Above normal precipitation is forecast for the lower Mississippi Valley, the Ohio and Tennessee Valleys, the Southeast, the mid-Atlantic and the Northeast. The remainder of the nation is not expected to exceed climatological values. Most of the spatial anomalies forecast below normal precipitation in the East.