Monday, June 29, 2015

Late-season Mississippi River flooding a concern for many

Typically springtime is when farmers, tug boat captains, the Corps of Engineers, and countless others whose livelihood depends on the Mississippi River anticipate high water. This year, however, the spring flood season was marked by minimal, if any, flooding. The Mid-South appeared to have made it through high-water season without a hitch. Unfortunately, the excess water was just late.

As we move into early July, recent heavy rain in the Mid-Mississippi River Valley and the Ohio River Basin has resulted rising water levels downstream. As shown in the graphic below, rainfall over the past 30 days has been double normal amounts in those areas, which all drain south into the river that flows past Memphis.

Accumulated precipitation for the past 30 days shows nearly double the normal precipitation upstream from the Mid-South.

As far as local precipitation, the past 30 days has featured accumulated precipitation that is above normal, however there is a major caveat in that data. Nearly 2" of rain fell right at the beginning on that 30-day window (May 31) and the amount above normal has decreased pretty much ever since. In fact, for the month of June to date, the total precipitation at Memphis International Airport is under 2.5", which is well below normal. Thus, the river can continue to rise towards flood levels even with below average precipitation for a 4-week period locally. Rain that falls locally, while having a significant bearing on the levels of tributaries and streams that flow into the Mississippi River, actually have little to no effect on the main channel itself here in Memphis.


The graphic below shows the current Flood Warnings (lime green with green outline) and Flood Advisories (green with no outline) in effect along the Mississippi River in the Mid-South. Flood Warnings are issued with flood stage is expected to be exceeded, while an advisory is issued when the river level will result in some impacts locally, but flood stage is not expected to be exceeded.

Flood Warnings (outlined) and Advisories (no outlines) line the Mississippi River throughout the Mid-South.
An article in this morning's edition of the Commercial Appeal details the impacts to local farmers, particularly those outside the levees in east Arkansas, of the late flood. In particular, thousands of acres of maturing soybeans are flooding with little chance of being salvaged this season. In addition, by the time the river recedes and fields dry, it will likely be too late to re-plant and get a full season of growth in before harvest time. Typically, these crops are planted after the "usual" spring flood season is over.

Flood stage for the Mississippi River at Memphis is 34.0 feet. This morning's stage was 28.5 feet and the river is expected to crest at 30.5 feet on Wednesday, July 8. Obviously, it doesn't take a stage of 34 feet to begin having an impact on local agricultural, and other, interests.

Today's Mississippi River stage and this week's forecast at Memphis is shown in the hydrograph above.
Just upstream, the river level at Osceola, AR, which also affects Tipton County, was 28.8 feet. Flood stage is 28.0 feet, thus the river is in flood at that location. It is expected to reach 30.5 feet by next Tuesday with possible additional rises thereafter. South of Memphis, the water level at Tunica is also expected to rise above the flood stage of 41.0 feet early next week. The river levels can be monitored anytime via the Mississippi River Forecast page on MWN.

Unfortunately for those who are hoping for a quick decrease in river levels, forecast precipitation in the Ohio/Tennessee River basins and Mid-Mississippi Valley shows a lot more water could be headed into the river here in the Mid-South (graphic below).

Forecast precipitation for the coming 7 days would indicate the likelihood of water levels remaining high on the river for the forseeable future.

Erik Proseus
MWN Meteorologist

----
Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Sunday, June 28, 2015

Pleasant weekend in the books, unsettled holiday week ahead

An unseasonably strong cold front dove through the Mid-South early Saturday morning, bringing with it drier and cooler air just in time for the weekend. With highs in the 80s and dewpoints in the low to mid 60s, the sunshine has resulted in pleasant days, rather than nature's sauna. Surface high pressure that is overhead this weekend will shift east though, meaning we're back in southerly flow by Monday and humidity levels will begin to increase.

Sunday mid-day surface analysis shows our recent cold front down near the Gulf coast while high pressure dominates the eastern U.S., bringing pleasant conditions.

Well above the surface, the eastern U.S. is dominated by a large trough of low pressure, which means the potential for unsettled weather. That pattern includes the Mid-South as cold fronts move by to our north, with the potential for thunderstorm complexes generated by these fronts diving south. These complexes are called MCS's (mesoscale convective systems) and we've talked about them before. They can be unpredictable both in the long term and the short term and they can bring damaging wind and torrential rain, as well as a lot of lightning.

In the Mid-South, they are most common in "northwest flow," which means the wind at the mid levels that drives storm complexes is blowing from the northwest, and that's the pattern we'll be in to some degree most of this week and right into next weekend.

The pattern at the mid levels this week will be dominated by northwest flow over the Mississippi Valley, as shown in this 500mb (18,000') forecast for Wednesday evening from the GFS model. A huge dome of high pressure over the western U.S. and general trough of low pressure over the eastern U.S. results in northwest wind over the Mid-South, which is a conducing pattern to unsettled weather and potential MCS activity from the Mid-South into the Ohio Valley.

As far as the forecast is concerned, though there is a very slight chance of a thunderstorm tomorrow, chances increase a bit Tuesday, then scattered thunderstorms are in the forecast for the remainder of the week. However, the main factor in our daily rain chances will be any MCS's that form and move into the area. Rain chances will be likely when one moves through, then probably dry for the rest of the day or night behind one as the atmosphere "re-energizes."

At this point we don't have our eyes on any one particular time period when one could affect the metro, so rain chances are fairly broad-brush. That's not good if you're planning to attend (or organize) a holiday fireworks display, so the best advice is check the MWN Forecast multiple times throughout the week as the forecast could change drastically from one day to the next as we get a better handle on timing of individual storm systems. For now, here's what we're expecting this week:



Erik Proseus
MWN Meteorologist

----
Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Panel discussion, July 1, 7:00pm: "The NWS - in 2015 and Beyond"

In recent weeks, a bill was introduced in a subcommittee of Congress ("The National Weather Service Improvement Act" - click to read) that would consolidate the forecasting operations for the United States from the current model of 122 "local" forecast offices to 6 "regional hubs."

Within the meteorological community (and not just at the NWS level), the outcry was immediate, including the NWS Employee's Organization, the broadcast community, and many others. Also outside the weather world, such as the emergency management spectrum (specifically the International Association of Emergency Managers), the pushback was also loud and clear. The chief complaints were that removing the forecasters from their local areas of responsibility would reduce forecast accuracy due to knowledge about local effects within an area being dispersed; that the local "touch" would be lost in areas such as collaboration with emergency management and response, local education outreach, and general relationship-building that takes place at the local level; and of course, the expected residual impact of the loss of hundreds or perhaps thousands of good meteorology jobs currently filled by experienced forecasters.

On the supporter's side, consolidation meant more collaboration between forecasters that are currently subdivided into their smaller areas of responsibility and more efficient (and thus lower cost) operations.

In fact, the response was strong enough that within just a few days the bill was stated to be amended to remove the consolidation in favor of a mandate that the NWS assess its severe weather watch and warning system to ensure that the public responds effectively to severe weather threats. Within five years of bill passage, the NWS, after careful evaluation and survey of users, would be required to have a new system of alerting the public in place.

On Wednesday night, July 1, at 7:00pm, MemphisWeather.net will host a panel discussion via Google Hangout on the implications of the recent Congressional action, the role and responsibilities of the NWS today, what they should look like in the future to most capably serve the public, and how the broadcast and private sectors can best partner with the NWS to assist in fulfilling their mission to protect life and property. Included in the discussion will be a conversation around the current watch/warning system and what changes might be proposed that would raise the level of awareness, and response, by the public to severe weather (convective, winter, tropical, and so on).

Panelists are being finalized but are expected to include NWS-Norman (OKC) Warning Coordination Meteorologist Rick Smith, WREG-TV broadcast meteorologist Austen Onek, Mississippi State University Meteorology graduate student and future NWS meteorologist William Churchill (representing the future of the NWS), and weather enthusiast and frequent MWN Hangout guest John Maddox (representing the general public voice). MWN meteorologist Erik Proseus will host the discussion.

We hope you will join us on Wednesday night for a great discussion on "The National Weather Service - In 2015 and Beyond."  There will be an opportunity for you to ask questions as well, including on the MWN Hangout page linked below, as well as on the Google+ event page . Watch our social media channels for details on how you can participate!

This event will be broadcast on the MWN Hangout page or can be viewed below on Wednesday night:




----
Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

Thursday, June 25, 2015

Thunder escorts much-welcomed cooler weather this weekend

Who's ready for cooler weather??


Wish granted! A very hot week featuring Heat Advisories and heat index values of 105-110° is coming to an end with one more hot day tomorrow (but not quite as bad as the rest of the week). The reason for slightly lower temperatures Friday will be more cloud cover and a few thunderstorms in the afternoon. Humidity levels will remain high, so heat indices will be in the lower 100s.

By tomorrow night, an unusual cold front (for summertime) will push into - and through - the Mid-South. This front will bring a high chance of thunderstorms with most in the Mid-South seeing a half inch to one inch of rain overnight. There is also a small chance that severe weather could occur, mainly in the form of damaging wind and, secondarily, large hail. The metro is currently in a Marginal Risk (category 1 of 5) zone, while areas just to our north are in a Slight Risk (2 of 5).


Most of the storms and rainfall will occur after dark Friday night, but if you have outdoor plans during the evening, you'll want to keep a close eye on StormView Radar and our Twitter feed via the MWN mobile app as storms could affect your plans.

By Saturday morning, rain should be over and, though it will be a warm start to the day with lows in the low 70s, much cooler and drier air will filter in throughout the day on a dare-I-say "refreshing" north breeze. As clouds move out, look for temperatures to peak about 10 degrees cooler than Friday, in the lower 80s. In addition, dewpoints (a measure of atmospheric humidity) will fall into the low 60s, making for a very pleasant afternoon and evening.

Very unusual for late June - a cold front diving all the way to the Gulf Coast as shown by the NOAA Surface Analysis forecast for Sunday morning.

Sunday will feature more pleasant weather with low humidity, sunny skies, and highs once again in the 80s. A slight warming trend takes place next week, but with rain chances increasing once again, looks for highs to remain primarily in the 80s with lows in the lower 70s.


Erik Proseus
MWN Meteorologist

----
Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!