Impulse responsible for today's showers to morph into another Nor'Easter

Today's showery weather in the Mid-South is the result of an impulse in the mid-levels of the atmosphere that is dropping southeast into the region from Missouri.  Over the next 72 hours, this impulse will move off the Mid-Atlantic coastline, strengthen, phase with a trailing impulse of energy, and explode into a Nor'Easter that will hit areas just affected by Hurricane Sandy last week with more strong wind, rain, and high surf.

The Nor'Easter is expected to exacerbate the damage in coastal areas with additional high water and certainly will frustrate those in the Northeast that are still without power, fuel, and other essentials.  More snow is expected inland from Vermont to western Massachusetts into southeastern (inland) New York and Pennsylvania. Strong wind could further damage fragile infrastructure and set back efforts to restore power and communications to coastal areas from Virginia to Long Island.  Below are snapshots from the GFS computer model showing the  progression of the energy creating this system.

Locally, behind this system, we'll be under the influence of a  trough of low pressure for another day before high pressure ridging takes hold, allowing temperatures to moderate heading towards the weekend.  Our next chance of rain and thunderstorms arrives early next week and it's cause can be seen in the last panel below as another trough moves into the Pacific Northwest. For the complete MWN forecast, click here.

500mb mid-level impulse over the Mid-South at 6pm Monday.
Huge ridge of high pressure over the western U.S.

500mb mid-level impulse moves to the SE Atlantic coast by 6pm Tuesday.
Trailing energy diving into Mid-South from Canada.

Lead impulse strengthens off the Mid-Atlantic coast by Wednesday late evening while
trailing energy catches up.  Nor'Easter in full swing for the Mid-Atlantic. Ridging building
into the Mid-South, starting a warming trend for late week.

Maturation of Nor'Easter as energy phases off the Northeast coast on Thursday evening.
Ridge centered over Mississippi River Valley - very pleasant weather locally.

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October 2012 Climate Data and Forecast Accuracy

For the first time in a year (since October 2011), Memphis International Airport finished the month with below normal temperatures as seasonal conditions, including multiple cold fronts, kept temperatures in check overall even with a few warm spells. In addition, precipitation was only slightly below normal, alleviating drought conditions a bit more this month, particularly across northwest MS.  There was one severe weather event, on October 17, which prompted Tornado Warnings in Shelby County and other parts of the metro area.  Funnel clouds were sighted but no tornadoes touched down.  Straight-line wind of up to 80 mph produced damage in Millington, TN.

Through October 31, the average temperature for 2012 of 69.0 degrees is 3.1 degrees above normal, making 2012 (still) the warmest year on record though the end of October, but only by 0.5 degrees (2007, 68.5 degrees).  Drought conditions abated somewhat with local and upstream rainfall and 2012 is no longer among the top 10 driest years on record, though precipitation for the year is still over 12" below average.  Most of the Memphis metro is now classified as being in a moderate-severe drought, down from extreme at the beginning of September.

Memphis International Airport, Memphis, TN

The average temperature for the month of October was 61.4 degrees, or 2.7 degrees below normal. The average high temperature was 71.4 degrees and the average low was 51.4. The coolest temperature of the month was 37 degrees on the 29th and 30th, while the highest temperature was 83 degrees on the 5th and 13th.  There were no days in which the high reached 90 degrees or higher.  There were no temperature records set or tied in October.

Precipitation for the month totaled 3.66", which was 0.32" below average. There were 8 calendar days with measurable rainfall, only 2 of which saw totals of 0.50" or more (maximum 1.48" on the 17th). The peak wind gust was 43 mph from the northwest on the 17th as severe weather struck the area with an average wind speed for the month of 8.3 mph. Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions, Bartlett, TN

The average October temperature at Cirrus Weather Solutions was 59.2 degrees with a maximum of 83.5 degrees on the 13th and a minimum of 33.1 degrees on the 30th.  October precipitation measured 3.04" via the automated gauge and 2.72" in a manual gauge used for the CoCoRaHS program (not including a small amount of rain that feel prior to 2:30am on October 1). The measured peak wind gust was 24 mph on the 1st. Average relative humidity was a muggy 74%. Click here for a daily recap on MemphisWeather.net.

MWN Forecast Accuracy

For the month of October, the average temperature error in all MWN temperature forecasts was 2.45 degrees, lower than all available full-range computer model data and the National Weather Service. 72% of the MWN temperature forecasts for the month were within 2 degrees of the actual temperature. MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). For dewpoint accuracy, the MWN forecast averaged 2.54 degrees of error and fell within 2 degrees of the actual dewpoint 63% of the time. Historical accuracy statistics can be found here.

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Download our iPhone or Android apps,  now with StormWatch+!
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