JULY 2013 30-DAY OUTLOOK
500 PM EDST Fri. June 28, 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.
Atmospheric and oceanic conditions over the tropical Pacific indicate persistent neutral conditions. Equatorial sea surface temperatures remain near normal west of 130 W longitude and below
normal over the eastern Pacific from 130 W to the South American coast. Average sub-surface ocean temperatures to a depth of 300 meters in the equatorial Pacific have warmed slightly in the last month and are now slightly above normal. There is a large volume of warmer than normal water below 50 meters in much of the equatorial Pacific to the west of 100 W longitude, and a region of cooler than normal water near the surface to the east of 120W. During the last month tropical convection was enhanced in the region around the Maritime Continent and suppressed over the central and eastern equatorial Pacific. The
enhanced convective phase of the MJO has been recently active over the Maritime Continent. Model forecast indicate the progression of the MJO eastward across the Pacific and into the Western
Hemisphere during the next couple weeks.
The MJO differs with the ECMWF and the GFS and its ensembles. The European brings the MJO wave into phase two, day 10 then into phase three which correlates to a cooler than normal temperatures for the Midwest, Ohio Valley on East while phase two warmer again in phase three as most models depict. The GFS still shows the MJO holding in phase one, but trending toward two but not until after the day 15. This is not a cool phase for the Midwest and Ohio Valley on East. It is cooler than normal farther south, the GFS could be still right. However, there is so much against this solution. Also, the GFS signal is stronger than the ECMWF.
The NAO and the PNA indexes are positive and is forecast to remain positive through day 14. The PNA index is negative and is forecast to remain negative through day 14.
Most of the long lead models forecast near to above normal temperatures for the nation. Except for the CMC1, the NCAR and the IMME. The NCAR forecast below normal in the West and the IMME forecast below normal across the northern Mississippi Valley.
Models are in agreement on the expected 500-hpa height pattern for July and depict a ridge over eastern Alaska, the West, and the western Atlantic. A trough is forecast off the Northwest coast, the central U.S., and northeast Canada. The high resolution runs are in agreement with their ensembles.

Above normal temperatures are forecast from the Plains to the West coast and northern New England. The probability of above normal temperatures for these regions is 57 percent. The remainder of the nation is not expected to exceed climatological values.

Below normal precipitation is forecast for the West coast, the central and upper Great Basin, and the Southwest. The probability of below normal precipitation across this area is 57 percent. Above normal precipitation is forecast for the Lower Mississippi Valley, the Southeast and portion of the lower mid-Atlantic. The probability of below normal precipitation is 55 percent. The remainder of the nation is not expected to exceed climatological values. Most of the spatial anomalies forecast below normal precipitation in the East.

Jim Munley Jr.
http://www.jimmunleywx.com