The first week of November is promising a nice round of Indian Summer warmth, getting us a head start on an expected overall warmer-than-normal month ahead. A warm and wet scenario is most likely thanks to contributions from a powerful El Niño-influenced pattern that started revving up in October. This contrasts sharply to last year’s colder and drier-than-normal November outcome.
Here is the current forecast estimate for Washington, D.C. (National Airport) for November 2015:
November average temperature forecast: 50.6 to 53.6, 1 to 4 degrees above normal (normal is 49.6 degrees).
Confidence: Medium to high on direction, but low on magnitude
November precipitation forecast: 3.5 to 4.5 inches of rain, 0.33 to 1.33 inches above normal (normal is 3.17 inches).
Confidence: Medium on direction, but low on magnitude
Here are some key factors involved in our November forecast:
Big warm start: Temperatures are forecast with high confidence to surge well above normal for the balance of this week with very comfortable 70s. That’s going to put us on a course for a warmer than normal month that will be difficult to reverse.
Our outlook is less confident for precipitation, but the extended range model guidance offers rain events through the 6-15 day range along with mostly warm temperatures (outside of a brief cool-down late this weekend).
El Niño: We are continuing to track one of the strongest events on record with the latest weekly data falling near or just slightly behind the biggest on record: 1997. November and big El Niño events have had mixed results in the past as the correlation to Mid-Atlantic weather is not as strong as during the core winter period, especially for temperatures. Most cases are wetter-than-normal as shown on the graphic below, but temperatures are more divided.
The years that experienced cooler Novembers on the East Coast tended to see more active western Pacific typhoon activity as that extra energy tends to trigger a more amplified North Pacific jet stream pattern that sends cooler air masses south from Canada. 1997 was a classic case of this with three super-typhoons in late October setting the stage for a sustainable cool pattern in the Eastern U.S. (last year’s Typhoon Nuri accomplished a similar feat for our very cool November). I include this typhoon conversation in our El Niño section because typhoons tend to be more active in the west Pacific with them. However, right now, the situation is very quiet, which suggests that warmer years like 1982 and 2009 may be more like this one.
Long-range models: The CFS model and the European model weekly outlooks have both been consistently favoring a warmer scenario for November. The maps below show the NOAA CFS model for the last 40 runs- notice their wet and warm look for the East Coast. They also keep poor Texas on the very wet side of the pattern, but not as much yet for California.
National Weather Service
The National Weather Service outlook is in strong support of this warmer-wetter thinking referencing the CFS model as well, but there is generally excellent support in other medium range models as well. You can read the Weather Service’s November forecast discussion here.
Review of October’s forecast – not so good
As our October outlook didn’t fare so well. We forecast above normal temperatures and precipitation and all three area airports ended up within one degree and one inch of normal thanks to varying weather regimes and no strong pattern signal really taking hold.
October average temperature forecast: 59.5 to 61.5, 0 to 2 degrees above normal (normal is 59.5 degrees).
Actual Temperature: 58.9F, 0.6 degrees below normal. Missed the forecast window by 0.6 degrees.
October precipitation forecast: 4.0 to 4.5 inches of rain, 0.6 to 1.1 inches above normal (normal is 3.4 inches).
Actual precipitation: 3.04 inches (0.36 below normal). Missed the forecast window by 0.96 inches
While both answers were very small misses vs. expectations, both were incorrect on the sign, so a “D” is given to the October forecast. It was a low confidence forecast, but one we ended up on the wrong side of.
Confidence is higher for November ahead, so let’s hope we can get some more passing grades.
To help better communicate the uncertainty in these monthly outlooks, I decided to add confidence descriptions to November’s outlook.
Let us know your thoughts in the comments!