JUNE-AUGUST 2017 90-DAY OUTLOOK
354 PM EDT Fri. Jun. 2, 2017
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.
Neutral conditions persisted in April, with near-normal sea surface temperatures observed across the central equatorial Pacific and above-average sea surface temperatures in the eastern Pacific. The latest weekly Nino index values were +0.5C in the Nino-3 and Nino-3.4 regions, and +0.3 and +0.8C in the Nino-4 and Nino-1+2 regions. The upper ocean heat content anomaly was slightly positive during April, reflecting the strengthening of above-normal temperatures at depth around the Date Line. Atmospheric convection anomalies were weak over the central tropical Pacific and Maritime Continent, while the lower-level and upper-level winds were near normal over most of the tropical Pacific. Overall, the ocean and atmosphere system remains consistent with neutral ENSO conditions.
The MJO forecast remains uncertain given forecast interference between the lower-frequency MJO signal, currently centered over the Maritime Continent, and other intraseasonal variability. The RMM index and CPC velocity potential MJO index each depicted a generally weak MJO signal over the past week, though the former now places the MJO enhanced phase over the Indian Ocean. Dynamical model forecasts are in generally good agreement on the forecast evolution of the MJO, but their solution is far from canonical. The models generally forecast eastward propagation across the Maritime Continent before weakening the signal, with the GEFS placing the enhanced phase over Africa and the western Indian Ocean by the end of Week-2, in what is likely to be a statistical result based on interference with the other modes of variability. The ECMWF solution is more consistent with canonical MJO evolution and is slightly favored over the other guidance.
The NMME forecast near to above normal temperatures across the nation for June, July, and August. The GFDL FLOR, the CMC1 CanCM3, and the NCEP CFSv2 depict below normal temperatures in the center of the nation. Most of the North American Multi-Model Ensembles depict above normal precipitation for the Northwest and the northern Rockies.
Above normal temperatures are forecast for the West Coast States, west of the Divide, the Gulf Coast States and the Southeast. Anomalies of 1-3F are forecast. The probability of below normal temperatures across this region is 56 percent. The remainder of the nation is not expected to exceed climatological values.
Above-normal precipitation is forecast for the Northwest, the northern and central Rockies, the Southeast, the lower Mid-Atlantic, the Ohio and Tennessee Valleys and the Midwest. The probability of above normal precipitation is 56 percent. In the Midwest and the Ohio and Tennessee Valleys, 57 percent for the Southeast and the lower Mid-Atlantic States and the northern Rockies. The remainder of the nation is not expected to exceed climatological values.
Jim Munley Jr.
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