The Pacific Transition (PT) pattern is a leading mode during August and September. This pattern captures anomalous wave-train of 500-hPa heights extending from the central subtropical North Pacific to the eastern United States. The positive phase of the PT pattern features above-average heights west of Hawaii and across western North America, and below-average heights in the Gulf of Alaska and over the southeastern United States.
The PT pattern is associated with above-average surface temperatures in the western subtropical North Pacific, the subtropical North Atlantic, and throughout western North America, and with below-average temperatures over the eastern half of the United States. The main precipitation departures associated with the PT pattern include above-average precipitation in the southeastern U.S., and below-average precipitation near Hawaii and across the northern tier of the United States.