Sunday, October 19, 2014

October 28 - November 1 Potential Storm System

A storm system may impact the US around an October 28 - November 1 time period.

Tropical Tidbits
The image above shows the 500mb height anomaly chart from the ECMWF model, valid on the morning of October 22nd. In this image, we see a weak disturbance forecasted to shift into southern Japan, then following the arrow I placed on this image, as the trough moves northeast. When applying the Typhoon Rule concept, which states weather phenomena that occurs in Japan is replicated in the US about 6-10 days later, a storm system may be expected to affect the nation around an October 28th to November 1st timeframe.

The image above shows forecasted anomalies for four different teleconnections. The forecast for the Pacific-North American (PNA) index is shown on the top-left, the North Atlantic Oscillation (NAO) is shown on the top-right, while the West Pacific Oscillation (WPO) and East Pacific Oscillation (EPO) forecasts can be viewed on the bottom-left and bottom-right panels, respectively. If we look at each teleconnection's outlook for the timeframe this storm may affect the US, we see the PNA may be negative, the NAO may be positive, the WPO negative and the EPO negative.

All of that tells me that when/if this potential storm begins to affect the United States, the jet stream may favor a storm track either north into the Plains, or down south along the Gulf Coast. The availability of cold air may vary, as the negative EPO favors cold air in the US, but the negative PNA restricts such cold air. If the storm goes along the South, it'll likely just push out to sea, as the positive NAO won't allow the storm to curve north along the East Coast, like a coastal Nor'easter storm. If it goes north into the Plains, the negative EPO may allow for some snowflakes to fly, but we'll re-examine that potential further on down the road.