Sunday, August 13, 2017

Summer takes another break, but makes a comeback this week

It's been kind of a strange summer. Certainly not overly hot other than a brief stint in mid-late July. In fact, since July 28, we've now had 16 consecutive days of below average daily temperatures and that will be extended at least three more days as we head into mid-August!

You can thank a series of fronts over the past couple of weeks that have moved over and through the metro for the additional cloud cover, periods of acceptable humidity levels, and scattered rainfall. That trend will continue as we head into the work and school week. The closest front is to our south but it is very weak, so wind direction is variable to southeasterly. As your Sunday progresses, a mesoscale convective vortex (MCV), or remnant weak low pressure left behind by a previous thunderstorm complex, will move across the Mid-South from the west as upper level flow pushes it east-northeast. This will bring a good chance of rain to the area later this afternoon and into the nighttime hours.

Simulated radar from the HRRR model through the early morning hours on Monday shows a large slug of moisture moving across the metro later this afternoon and into the early nighttime hours. You'll notice the distinct "spin" in the area of potential thunderstorms on the back side of the rain area. That is the low pressure system driving the precip, what we call a mesoscale convective vortex (MCV). (WxBell) 

A few thunderstorms are possible, mainly south of the city where a Marginal Risk (level 1/5) of severe weather exists. I do not expect to see any strong storms in the metro. Rainfall totals could rise to a half-inch to inch in some spots by Monday morning.

A low-end severe weather risk exists for the far southern portions of the metro today. I expect no severe weather for most of the metro and only a low chance of thunder north of the MS/TN state line.

The week ahead

In the wake of the rain today and tonight, Monday looks to be drier though a chance of storms is in the offing, mainly south of the city. Though humidity will be back in the "muggy" category, temperatures remain mild with highs in the mid 80s due to only partly sunny skies.

Additional scattered showers and thunderstorms will be possible nearly each day throughout the week and into next weekend, although not everyone will see rain every day. In fact, rain chances diminish some mid-week as upper level high pressure begins to build to our south and push north a bit. That will squash rain chances a bit, leaving a few possible in the heat of the day.

Speaking of heat, it's making a comeback under this high as well. We'll be back above 90° by Wednesday with dewpoints getting closer to the "miserable" range as they near 75°. That'll mean heat indices back above 100° and overnight lows that get no lower than the mid 70s. The mugginess could subside a bit by next weekend as the pattern shifts just a bit, but typical summer weather will continue right into the weekend.

Forecast temperatures for the next 10 days from the National Weather Service "National Blend of Models" (NBM), which averages today multiple models to depict the best possible forecast using them all. (WxBell)

Eclipse Forecast

I know everyone's keen interest is on the eclipse forecast a week from tomorrow, August 21. Eight days out can still be a crap shoot as far as cloud forecasts, but the overall pattern doesn't necessarily bode well. Of course, a couple hours of partly cloudy skies is all we need, but it doesn't appear Eclipse Day will be a bright sunny day dominated by high pressure at all levels. Stay tuned and cross those fingers!! Starting tomorrow, eclipse day will be in the extended range forecast on your MWN app!

For more on viewing the eclipse in the Memphis area, see our Viewing Guide if you haven't already!

Erik Proseus
MWN Meteorologist

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Saturday, August 12, 2017

July 2017 Climate Data for Memphis, TN

July Climate Recap

After consecutive months of below average temperatures, an anomaly in recent history, July moved back above average, but just barely. The average temperature of 83.1 degrees was about one-half degree above normal. The month as marked by a very hot spell in the third week of the month with mid to upper 90s on several consecutive days and Excessive Heat Warnings posted as heat indices climbed above 110 degrees. Slightly cooler than average weather started and ended the month.

Precipitation was fairly variable across the metro due to the nature of summertime thunderstorms. To wit, Memphis International Airport ended up with just under 4" of rain and at a deficit for the month, while MWN in Bartlett recorded over 5", which was above the July average. Most of the rain fell in the early and latter stages of the month with a hot spell mid-month resulting in little precipitation. Another example of the sporadic nature of the precipitation lies in the storm reports for the month. Flash flooding was reported in multiple locations in the metro on the 15th, yet both Memphis International Airport and MWN recorded no measurable precipitation for the date. A couple of hail and wind reports were recorded with pulse thunderstorms on various days of the month but no widespread severe weather occurred.

Memphis International Airport, Memphis, TN

Average temperature: 83.1 degrees (0.4 degrees above average)
Average high temperature: 92.3 degrees (0.7 degrees above average)
Average low temperature: 73.9 degrees (0.1 degrees above average)
Warmest temperature: 99 degrees (21st)
Coolest temperature: 67 degrees (30th)
Heating Degrees Days: 0 (0 above average)
Cooling Degree Days: 571 (22 above average)
Records set or tied: None
Comments: 23 days recorded temperatures at or above 90 degrees, which is 2 more than an average July. Year to date, the average temperature of 65.7° remains the second warmest on record behind 2012.

Monthly total: 3.91" (0.68" below average)
Days with measurable precipitation: 8 (0.8 days below average)
Wettest 24-hour period: 1.50" (23rd)
Snowfall: None
Records set or tied: None
Comments: Year to date, precipitation has totaled 27.37" or 84% of normal.

Peak wind: North-northeast/33 mph (14th)
Average wind: 6.3 mph
Average relative humidity: 73%
Average sky cover: 40%

Click here for a daily statistical recap for Memphis International Airport.

Cirrus Weather Solutions /, Bartlett, TN

Average temperature: 81.5 degrees
Average high temperature: 92.3 degrees
Average low temperature: 71.7 degrees
Warmest temperature: 98.7 degrees (22nd)
Coolest temperature: 61.1 degrees (30th)
Comments: None

Monthly total: 5.18" (automated rain gauge), 5.26" (manual CoCoRaHS rain gauge)
Days with measurable precipitation: 9
Wettest date: 1.26" (28th) (via automated gauge)
Snowfall: None
Comments: No measurable rain fell from the 9th-22nd, nearly two weeks.

Peak wind: Northwest/27 mph (1st)
Average relative humidity: 79%
Average barometric pressure: 30.00 in. Hg
Comments: None

Click here for a daily statistical recap for Bartlett, TN.

MWN Forecast Accuracy

MWN average temperature error: 1.27 degrees (tied for most accurate month of forecasts in 20 years of record-keeping!)
MWN forecast temperatures within 2 degrees of actual: 87%
MWN average dewpoint error: 2.02 degrees
MWN forecast dewpoints within 2 degrees of actual: 68%

MWN's forecasts extend out five periods (2.5 days, or roughly 60 hours). Historical accuracy statistics can be found here.

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

Friday, August 4, 2017

Beat the heat with a cool (but rainy) August!

A cool first half of August looks to be in the offing, but the only way we get that is with more clouds and rainfall than normal. Hopefully you're ready for the trade-off!

Temperatures the past several days have averaged a bit below the normal of 92°. As we head into the weekend, another cold front today kept temperatures at bay once again (though dewpoints are still well into the muggy range). We'll be on the "cool" side of the front tomorrow with what should be a pleasant day as the sun returns and the mugginess also falls, albeit briefly. Temperatures will drop into the 60s tonight for all and top out in the mid to upper 80s Saturday.

Surface map for Saturday morning shows high pressure (briefly) in control of Mid-South weather, providing for a nice day overall. (NWS)

By Sunday though, the front returns north as a warm front, putting us back in the muggy sector. Meanwhile, the first in a series of upper level waves moves in from the west, bringing high chances of rain and some thunderstorms, perhaps a few marginally strong, by afternoon and evening.

By Sunday evening, the cold front will have surged back to the north as a warm front and we'll be in the "warm sector" of a low over IL, meaning a good chance of thunderstorms. (NWS)

With the front more or less stalled out across the region next week, a gravy train of upper level disturbances will move through on "zonal flow" (meaning that the upper level patter is fairly uniform from west to east). Waves of rain and storms will affect the region throughout next week. In fact, in the 7-day forecast, I don't have rain chances below 40% on any day after tomorrow.

The upper level pattern by Tuesday evening features a mainly west-to-east flow across the southern U.S. "Ripples" in that flow will provide the lift necessary to generate showers and thunderstorms. (PivotalWx)

It's still too early to determine when the heaviest or strongest storms might be (and a few could potentially be strong), or even when the dry periods will be next week. But for now, it looks wet from sometime Sunday afternoon through at least sometime Monday. After that, models don't agree on the exact positioning of the front each day next week, which will be the main factor in the rain and storm chances each day. For now, plan on highs remaining in the 80s (probably no warmer than mid 80s), lows in the lower half of the 70s, and mugginess and daily rain chances remaining a factor. Not necessarily the best forecast for everyone that is gearing up to send kids back to school!

Forecast rainfall through next Friday morning shows a large swath of 3-5" across the middle portion of the country, including the Mid-South. (NOAA/NWS)

Looking past this week, the week 2 outlook from NOAA indicates a likely continuation of the cool, wet pattern into mid-August. Let's hope that the pattern breaks in time for the solar eclipse on August 21. Clouds are definitely NOT something we want that day!

For the period August 11-17, the trend is for above average precipitation according to NOAA.

For the period August 11-17, the trend continues for below average temperatures, according to NOAA.
Good luck this year to all the teachers, staff, students, and parents who are in the throes of new routines this coming week! Be sure to check out the MWN app each morning to see whether you'll want to send an umbrella or other rain gear with the kiddos!

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!
MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder