WEATHERAmerica Summer Season Forecast For 2006

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(NOTE: Graphics For This Outlook Can Be Found At:

Eastern US Weather Forums -> Weather forecasting and discussion and

CanadianWeather.org )

 

Overview

 

The one notable aspect of the spring months has been the relative lack of a heat ridge in the Bermuda position. Typically, 500MB height rises will take shape over the Sargasso Sea during April, with a slow north and west lurching motion when viewing atmospheric height mean charts. This year, the only sign of a subtropical high within the Atlantic Basin has been over the Greater Antilles and Caribbean Sea. So a minimalist forecast for hot weather seems appropriate in locations that are likely to stay north of the positive height anomaly, with the highest readings likely to take shape in the Southeast as the ridge becomes anchored, most likely centered in the Atlanta/Macon GA corridor.

 

While the western states have seen some very chilled anomalies (with cutoff lows in S CA during later April), rapid rebounds in atmospheric heights and thicknesses have been noted through the West and especially the Great Plains. A flat subtropical high has also emerged recently north and west of HI into the Philippines. As this ridging gains in latitude and controls the western rim of the Pacific Ocean, teleconnections point toward a resurgence of the Sonoran heat ridge. Rapidly displacing the onslaught of cold mP surges and shortwaves, I suspect that much of the western U.S., especially the Puget Sound and Columbia Basin, will see a reversal in trends and sharp change to hot/dry conditions that will occasionally take over the CA Central Valley and other sectors of the Intermountain Region. Parts of the heartland and the Desert Southwest, being in between the cores of the heat ridges, may see essentially normal summer conditions. I suspect that energy cresting the western ridge complex will eventually build a trough over the Great Lakes and Corn Belt, resulting in lower maxima through much of eastern Canada and adjacent areas of the Midwest and Northeast.

 

Temperatures

 

A long, hot summer? Well if you live in the western and southeastern states, probably yes. But I must add that a widespread, long lasting thermal anomaly is unlikely for two reasons. One is the obvious late start of building a subtropical high in the Southeast. The other is the still-active polar westerlies. While the jet stream will revert northward, the likely presence of a vigorous ridge complex in the western states would seem to favor digging of energy from the Prairie Provinces into the Great Lakes/Corn Belt and then the Northeast. So much of eastern Canada should stay cool, and near normal values the likely outcome from the Midwest into the Mid-Atlantic and New England states.

 

Precipitation

 

Concerns for large scale drought should fade over the lower Great Plains and Mid-Atlantic states by June, largely as a result of shifts in the upper level wind patterns. However, water supplies look to be tested in two regions: the western and southeastern states, which is where heat ridges are likely to become established through much of the summer. The presence of a strong positive height anomaly in both locations may actually help moisture advection for both the "monsoon" season in the Desert Southwest and "popcorn" convection in the midsection of the nation.

 

The best convective potential will probably set up from the Upper Mississippi Valley into the Northeast, with thunderstorm and severe weather production (either via supercells, spearhead storms, or MCC development) increased. Tropical systems could end up as a huge enhancement of rainfall production, particularly in the southern tier but also along the East Coast later in the summer and into early fall.

 

Tropical Cyclones (Atlantic Basin)

 

Unless the thermal profile of the Pacific Ocean changes character toward a thoroughly warm El Nino (all sectors of the equatorial regions rising into a positive SST anomaly), we are headed for our third straight badly damaging hurricane season. The overall character of the 500MB forecast would seem to favor tropical cyclone output and landfall possibilities falling somewhere in between 2004 and 2005, certainly not good news for the state of FL. The additional specter of merging heat ridges (Sonoran + Bermudan) makes for an increased risk to TX, possibly in August and/or September. In addition, during early autumn, as the ridge complex shifts ever westward, possibilities exist for tropical cyclone interaction with a mean trough in the Great Lakes and Midwest; this the Atlantic Coastal Plain may have potential for mayhem that has largely been missed during the past two years. Overall numbers of tropical systems should be high, although the landmark 2005 season total should not be threatened; the ITCZ is about 3/4 as active as a year previous, with gaps in convective pulsation occurring (see full disc satellite views and note relative quiet in the Indian Ocean frame).

 

PREDICTION FOR 2006 Hurricane Season:

 

2 Subtropical Storms

20 Named Storms

10 Hurricanes

5 Major Hurricanes

1 Super Hurricane

 

June

Some danger of development in western Gulf of Mexico; perhaps one named tropical storm or a tropical depression. Wind impacts minimal, but if 500MB weakness persists as forecast TX, LA coasts and Arklatex vicinity may be affected by excessive precipitation. Odds of U.S. tropical storm strike: 1 in 12.

 

July

"Cape Verde" type waves may get off to a running start if a) positive thermal anomalies persist and grow in eastern Atlantic Ocean and b) ridging extends from southeastern U.S. through Sargasso Sea. Impact on Lesser Antilles or even Puerto Rico and Hispaniola is possible. Odds of U.S. (Territory) hurricane strike: 1 in 10.

 

August

Tropical cyclone formation should get in gear as African waves ride underneath mid-Atlantic Ocean ridge and reach Greater Antilles with perhaps as much as three major impacts. S FL and S TX could see interaction with a major hurricane. Odds of U.S. hurricane strike: 1 in 4.

 

September

I suspect that the ninth month will be the most dangerous in terms of both intensity of tropical cyclones and possibilities for an impacting (as opposed to grazing) landfall on a U.S. coastline. With waters at their warmest, and the heat ridges at their most inland and northern positions, westward moving hurricanes may strike FL, Gulf Coast points (TX highly suspect), OR along the Eastern Seaboard (Carolinas or SE VA). If ENSO conditions maintain the "wobbling neutral" character and 500MB troughing begins to assert itself across the Great Lakes, a system along the lines of Hugo (1989) Isabel (2003) or Floyd (1999) could appear. Odds of U.S. hurricane strike: 1 in 3.

 

October

With ridging receding and the 500MB trough beginning to anchor through the Great Lakes and Tennessee Valley, emphasis will shift to the Eastern Seaboard for hurricane strike threats. A Caribbean Sea hurricane may also appear with threats to resorts and perhaps to AL or N FL. Later in the month, older frontal structures or isolated cold core lows could give rise to subtropical storms in the western Atlantic Ocean. Odds of U.S. hurricane strike: 1 in 6.