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2006 Summer Outlook

Matt Ross @ 12:00 AM


Today will be a beautiful April-like day, sunny and breezy with highs near 70 degrees. Tomorrow will begin a gradual warmup into summer as highs hit the mid 70s. See Jason's post from yesterday for the forecast for Thursday through the holiday weekend.

2006 Summer Outlook

The summer outlook, just like all long range outlooks, comes with a good deal of uncertainty. While there is sound scientific basis for the predictions, it is done primarily as an experiment and learning experience, and should be viewed as such. While there is a moderate level of confidence in the overall idea, the specifics come with a higher level of uncertainty.

The primary factors that went into predicting the 2006 summer were current, forecast, and evolution of sea surface temperatures (SSTs) in the equatorial pacific (ENSO), local and national temperatures and snowfall in December-March of this past winter, and the evolution of the overall pattern in April and May. Secondary factors that were considered were global indices such as the PDO, QBO, and recent overall global patterns and trends of the past several years.

Currently SSTs in the Equatorial Pacific are in the neutral or average range after being in a weak La Nina (cold) state this past winter. Current consensus forecasts are for neutral conditions to persist throughout the summer, with possible slight warming as we head toward the fall.

This past winter saw overall warm temperatures in the continental United States with the warmest anomalies centered in the upper Plains and Great Lakes. This area should also feature the warmest temperatures with respect to average this summer.

April was a very warm month for the US, while May has been quite cool in the mid Atlantic and northeast.

The QBO is positive (west) and will remain such and likely strengthen throughout the summer.

The official forecast for the summer to be measured at National Airport (DCA) is as follows:
  • Overall Temperatures: Normal
  • Overall Precipitation: Normal
  • 90+ degree days for June, July, August: 25-30 (average is 32)
  • Days of 95+: 3-5
  • Chance of a 100+ day: 20%
June: +1F to +2F

June is the best candidate for the driest month of the summer. A strong ridge will develop over the east toward the very end of May and should persist through much of the month of June. We will see 7-10 90+ degree days and temps will frequently be in the mid to upper 80s for daytime highs.

July: Normal

July should see normal temps and normal precipitation. Of course for DC this is quite warm. We will see frequent highs in the upper 80s with lows around 70. We will likely see 8-12 90+ degree days. If I had to lean one way or the other, I would say July will be slightly below normal rather than above.

August: -1F to -2F

August is the best candidate for wettest month of the summer and most likely for us to get affected by a tropical system. We may find that June temperatures near or exceed the average for August, even though historically it is almost 3 degrees warmer. We will likely see cooler than normal temps during the beginning or warmest part of the month, with a slight warmup toward the end heading into September. We will see 7-10 90+ degree days.

Most influential analog summers were 1921, 1925, 1976, and 1990.

NOAA Hurricane Outlook

The National Weather Service issued their Hurricane Outlook yesterday, and called for an 80% likelihood of seeing an above average hurricane season. More specifically they are predicting 13-16 named storms, 8-10 hurricanes, and 4-6 major hurricanes (Category 3+). On Bloomberg Radio, meteorologist David Tolleris (DT) mostly agreed with the outlook, but felt that the number of hurricanes would be slightly lower and that a lot of them would recurve and either miss or just skim the Atlantic coastline. I tend to agree with DT. While there is certainly the possibility of some strikes to the US coastline, there will be significantly less named storms than last season, and many storms will miss the US completely.

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