The tranquility of November

. . .is usually replaced with some rough weather ahead as we move closer to winter. As many people are enjoying the “Indian Summer”, do know that some signals are pointing towards a stormier pattern ahead. Based on patterns, I would especially be cautious with the Thanksgiving weekend, but that is more gut speaking now as the modeling is unreliable at that time stamp.

The beginning of this week will feature above normal (in some cases, much above normal) temperatures for much of the country east of the Rockies, with a gradual cooling trend by mid-week. Showers and thunderstorms will be possible from the Mid-Mississippi Valley eastward toward the Mid-Atlantic through Wednesday.

00z GFS sea level pressure and 6 hour precipitation forecast valid at 7 pm EST on 11/13/11.

The next weather-maker starts organizing today with deep south-southwesterly flow pulling up warm temperatures and deep moisture from the Gulf of Mexico. The only area of possible showers may break out in the Ohio Valley up through the Great Lakes region, but amounts look light.

00z GFS sea level pressure and 6 hour precipitation forecast valid at 7 pm EST on 11/14/11.

By tomorrow, the moisture is starting to pool along the front and a more pronounced area of rain and some thunder starts to break out from Texas up through the southeastern Great Lakes and northern Mid-Atlantic. The Storm Prediction Center is isolating an area in central Texas for possible severe weather, but this seems to be a rather small possibility for now.

00z GFS sea level pressure and 6 hour precipitation forecast valid at 7 pm EST on 11/15/11.

By Tuesday evening, a system rounds the base of the trough that is now established over the Central Plains and precipitation starts moving further north towards the Mid-Mississippi Valley, Ohio Valley, and Mid-Atlantic regions. The Gulf Coasts of TX through LA start to get in on the fun with showers and thunderstorms becoming more numerous. Not drought-busting, but anything is great right now.

00z GFS sea level pressure and 6 hour precipitation forecast valid at 7 am EST on 11/16/11.

Finally, by Wednesday morning, the trough starts moving east along with rain and imbedded thunderstorms. Some areas of heavy rain could be possible with this system Tuesday night through early Wednesday from VA through MD, DE, southeastern PA, and NJ. This doesn’t look to be a major storm as the trough never really amplifies, therefore a period of heavy rain is the outcome with no snow.

Speaking of snow, look at the 384 hour forecast of the GFS. Although this is not a reliable forecast (as it is out 16 days), it shows where the pattern may be heading and I’ll start focusing on this for future posts. For now, I wouldn’t worry too much about a major East Coast snowstorm, but the pattern may be turning colder around Thanksgiving.

00z GFS sea level pressure and 12 hour precipitation forecast valid at 7 pm on 11/28/11.

My final thought is to show you the Madden-Julian Oscillation (MJO) forecast for the next 16 days. This is mainly used for the tropics, but does have a bearing on precipitation episodes in North America as well. One curious aspect is that there has been some model rumblings for a potential tropical development in the Caribbean by next week. The MJO is favorable for development, even this late in the season. Meanwhile, with the Pacific North America (PNA) pattern forecasted to be negative and the North Atlantic Oscillation (NAO) neutral, I would expect to continue with warmer than normal temperatures for the next week or two. I will explain these patterns more in future posts.

The GFS ensemble plume forecast for the MJO. Octant 8 and 1 are favorable for tropical development in the Atlantic.

Thanks for reading!

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