Browse Month

October 2010

My winter forecast (temperature only for DJF)

Not your typical Nina scenario… anomalies are in degrees Fahrenheit.

EXPLANATION:
I’ll just start off by saying that I’m not big into long range forecasting. I do it as part of my job at work, so I figured since I put in the effort to do it there I may as well show you all the results. As an aside for verification, my analogs did fairly well in September (I finished at/near the top amongst the forecasters at work), and they also caught on to the October transition that we are currently seeing.

METHODOLOGY:
When finding my analog years, I like to keep things simple. I used years that went from Nino to Nina status and found the ones that had similar seasonal temperature anomalies to this year, particularly JJA. Better analogs were weighted more in order to match up the temperature patterns more closely.

ANALOGS:
in [year (weight)] format

2005 (more)
1995 (more)
1988 (normal)
1983 (normal)
1998 (less)

What to Watch Fore(cast) – Oct 4-10

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Highlights:

Hot and dry in the North Country – An area of high pressure will keep the Northern Plains relatively hot and dry this week.

Cool and rainy in the Southwest – A cut-off low will bring clouds, rain and cool temperatures to the Southwest throughout the work week.

Near normal after a cool start in the East – The East Coast will be cool over the next few days as a cut-off low lingers over the region. As it moves out, sunny and seasonal weather will move in.

Frigid start in the Southeast – The next couple of days will be chilly in the Southeast as lows fall into the upper 30s to mid 40s throughout most of the interior.

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Discussion:

The weather pattern will be changing slowly during the first half of this week as an omega block (trough-ridge-trough pattern) sits over the country. The cut-off low over the eastern U.S. will lift out of the region late in the work week, which will allow the upper-level ridge to slowly move east and eventually break down sometime next week. The ridge of high pressure will keep the North Country relatively warm and dry this week as the warmer conditions slowly spread over to the East Coast this weekend. The cut-off low over the East Coast will bring below normal temperatures to the East through mid-week. This cool air is especially noticeable in the Southeast, where the drier air is allowing lows to fall into the upper 30s to mid 40s throughout most of the interior Southeast. Closer to the coasts, the cooler temperatures are less dramatic.

Another cut-off low will anchor itself over the Southwest throughout the week, bringing rain and cooler temperatures to the region. The cut-off low will try to escape the region as it lifts into the Rockies at the end of the work week, only to get blocked by the upper-level ridge as it stops just short of the Central Plains.

Given the volatility of the current weather pattern, anything beyond the end of the week is somewhat uncertain. The block appears to break down early next week, which will allow for a very dynamic and likely interesting period for weather enthusiasts.

New weather pattern in the works?

After a long, long period of having a subtropical ridge anchored over the Southeast, it appears as though the long-wave pattern has finally shifted, with an upper-level ridge over the Desert Southwest and Plains and a trough over the Mid-Atlantic and Northeast. This will mean warmer weather for the Southwest and cooler, disturbed weather for the Mid-Atlantic and Northeast.

The next couple of weeks appear to be rather turbulent weather-wise as the Northern Hemisphere transitions into the winter weather pattern. Cut-off lows, blocking ridges, the potential for powerful low pressure systems and tropical systems near the U.S. are all possible as we head into October. With so many things possible in the future, forecasting anything beyond five days will be extremely difficult, so don’t be surprised if your extended forecast makes dramatic shifts this month.

The GFS model has been hinting at a powerful mid-latitude system in the 10-12 day range, which could mean some interesting weather and an awesome chase day for myself and Jason, but we’ll have to wait and see what pans out.