Back on April 27th when the EF-5 tornado struck the Wrangler plant in Hackleburg, it carried blue jeans to Soddy-Daisy, Tennessee. How in the world did they get there? Dual-pol’s CC value (correlation coefficient) helps explain how that probably happened – out the top of the thunderstorm and into the air roughly 30,000 feet above the surface.

This image from the NWS Tulsa shows how the CC value is indicating that there is something that might be debris being thrown east of the Moore and Shawnee, Oklahoma tornadoes – in the anvil miles ahead of the thunderstorm:

Image from NWS Tulsa

Correlation Coefficient is a product that measures the correlation of the horizontal and vertical backscatter of power in the radar’s sampling. That’s a big way of saying since dual-pol radar sends out a pulse oriented in the vertical and in the horizontal, we can look at how those different pulses behave to see if precipitation is uniform (like ALL rain or snow) or if it is variable (like debris or a wintry mix).

If you’re interested in learning more about this, I suggest you look at the online training from the Warning Decision Training Branch of NOAA.

-Jason
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Friday looks like a beautiful early April day with a high in the lower 70s, a north breeze at 10 to 20 miles per hour, sunshine and low humidity. The problem is, it’s not early April; Friday is May 24th! May temperatures are still running a little over 3 degrees below average (3.4º F to be exact), so Friday’s weather really fits the mold of how this entire month has worked weatherwise.

There is a warm-up coming this weekend after a chilly Friday night and Saturday morning; lows will drop as low as 41 to 47 degrees around the Tennessee Valley by Saturday morning. Saturday morning’s record low in Huntsville is 45º set in 1942.

The rest of the Memorial Day Weekend weather, including the beach and The Smokies, is posted at WHNT.com/Weather!

Climate Data for May 24th
Sunrise: 5:38 AM
Sunset: 7:50 PM
Average High: 83 Record 96 (1996)
Average Low: 62 Record 43 (1931)

Hours of Daylight: 14:11 (Same as Thursday)

-Jason
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There will still be some severe weather episodes west and north of us in the Plains, Midwest, and even Canada through June, but the long-term weather pattern around here suggests that it’s about to feel more like it should for this time of year after this final cool snap that makes it unusually chilly at times for the start of the Memorial Day Weekend (see WHNT.com/Weather for the weekend outlook).

So now, we shift gears from forecasting cool snaps and worrying about threats of widespread severe weather to tracking summertime storms (that can still be strong at times) and watching the tropics.

It’s been a long time since the ensembles like this one have put the big red bullseye on the South; much-above average temperatures are expected for the first week of June thanks to a strong ridge building in over the region over the next two weeks:

This ridge over the East is in a perfect position to keep temperature near average or a little warmer than average through early June, but it also sits in a spot that makes tropical development a possibility in the Caribbean or southern Gulf of Mexico.

Hurricane season starts June 1st and runs through November 30th; NOAA released their forecast for an “above average” season this morning.

If you’ve got Memorial Day beach plans or even for the following week and/or weekend, you’ve got nothing to worry about when it comes to tropical cyclones.

Having said that, with that ridge over the East from next week through the first two weeks of June, seeing some development in the Eastern Pacific is likely (that won’t impact the Gulf); some development may even be possible between May 31 and June 6 in the Caribbean or Gulf.

Sea surface temperatures are beginning to get warm enough in the southern Gulf and Caribbean for minimal development. Here’s a look at SST’s (sea surface temps) and two frames of the GFS model showing an Eastern Pacific storm and some unsettled weather in the Gulf and Caribbean:

-Jason
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In its 2013 Atlantic hurricane season outlook issued today, NOAA’s Climate Prediction Center is forecasting an active or extremely active season this year.

For the six-month hurricane season, which begins June 1, NOAA’s Atlantic Hurricane Season Outlook says there is a 70 percent likelihood of 13 to 20 named storms (winds of 39 mph or higher), of which 7 to 11 could become hurricanes (winds of 74 mph or higher), including 3 to 6 major hurricanes (Category 3, 4 or 5; winds of 111 mph or higher).

These ranges are well above the seasonal average of 12 named storms, 6 hurricanes and 3 major hurricanes.

“With the devastation of Sandy fresh in our minds, and another active season predicted, everyone at NOAA is committed to providing life-saving forecasts in the face of these storms and ensuring that Americans are prepared and ready ahead of time.” said Kathryn Sullivan, Ph.D., NOAA acting administrator. “As we saw first-hand with Sandy, it’s important to remember that tropical storm and hurricane impacts are not limited to the coastline. Strong winds, torrential rain, flooding, and tornadoes often threaten inland areas far from where the storm first makes landfall.”

Three climate factors that strongly control Atlantic hurricane activity are expected to come together to produce an active or extremely active 2013 hurricane season. These are:

A continuation of the atmospheric climate pattern, which includes a strong west African monsoon, that is responsible for the ongoing era of high activity for Atlantic hurricanes that began in 1995;

Warmer-than-average water temperatures in the tropical Atlantic Ocean and Caribbean Sea; and

El Niño is not expected to develop and suppress hurricane formation.
“This year, oceanic and atmospheric conditions in the Atlantic basin are expected to produce more and stronger hurricanes,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster with NOAA’s Climate Prediction Center. “These conditions include weaker wind shear, warmer Atlantic waters and conducive winds patterns coming from Africa.”

NOAA’s seasonal hurricane outlook is not a hurricane landfall forecast; it does not predict how many storms will hit land or where a storm will strike. Forecasts for individual storms and their impacts will be provided throughout the season by NOAA’s National Hurricane Center.

New for this hurricane season are improvements to forecast models, data gathering, and the National Hurricane Center communication procedure for post-tropical cyclones. In July, NOAA plans to bring online a new supercomputer that will run an upgraded Hurricane Weather Research and Forecasting (HWRF) model that provides significantly enhanced depiction of storm structure and improved storm intensity forecast guidance.

Also this year, Doppler radar data will be transmitted in real time from NOAA’s Hurricane Operations Center Hurricane Hunter aircraft. This will help forecasters better analyze rapidly evolving storm conditions, and these data could further improve the HWRF model forecasts by 10 to 15 percent.

The National Weather Service has also made changes to allow for hurricane warnings to remain in effect, or to be newly issued, for storms like Sandy that have become post-tropical. This flexibility allows forecasters to provide a continuous flow of forecast and warning information for evolving or continuing threats.

“The start of hurricane season is a reminder that our families, businesses and communities need to be ready for the next big storm,” said Joe Nimmich, FEMA associate administrator for Response and Recovery. “Preparedness today can make a big difference down the line, so update your family emergency plan and make sure your emergency kit is stocked. Learn more about how you can prepare for hurricane season at http://www.ready.gov/hurricanes.”

Next week, May 26 – June 1, is National Hurricane Preparedness Week. To help those living in hurricane-prone areas prepare, NOAA is offering hurricane preparedness tips, along with video and audio public service announcements in both English and Spanish, featuring NOAA hurricane experts and the FEMA administrator at http://www.nhc.noaa.gov/prepare/.

NOAA’s outlook for the Eastern Pacific basin is for a below-normal hurricane season and the Central Pacific basin is also expected to have a below-normal season. NOAA will issue an updated outlook for the Atlantic hurricane season in early August, just prior to the historical peak of the season.
NOAA’s mission is to understand and predict changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Join us on Facebook, Twitter and our other social media channels.

Temperatures tumble over the next several days. Enjoy the next several days as temperatures average at or slightly below normal for afternoon highs. This time of year we could very easily be sweating it out in the lower to middle 90s. As we know, those days are coming very soon. Next week, we could be in the upper 80s to near 90. The reason for the cooler weather is a trough of low pressure in the upper atmosphere. A huge ridge at the surface protects us from any significant rainfall for a while. Here is the map valid for Saturday morning. The yellow and green indicate some of the cooler air.

Here is the temperature trend over the next 5 days. This is only part of the story. Friday, Saturday, and Sunday several areas could dip into the middle to upper 40s. If you live a valley or in southern middle Tennessee, you have the best of the cooler weather. Enjoy!

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Anytime you’ve got weather to report or you want to make sure you see your comment or photo on Twitter, use the hashtag #valleywx!

-Jason
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Cooler air settling in Thursday night and a clearing sky should allow temperatures to dip into the upper 40s and lower 50s by Friday morning. This push of cool air will not be as significant as the surges of cold weather earlier this month, but temperatures will continue to run about 3 to 7 degrees below average through the first part of the Memorial day weekend.

For the full weekend forecast (it’s a nice one), check out the main weather page at WHNT.com/Weather!

Climate Data for May 23rd
Sunrise: 5:39 AM
Sunset: 7:49 PM
Average High: 83 Record 95 (2010)
Average Low: 61 Record 45 (1954)

Hours of Daylight: 14:11 (2 minutes longer than Wednesday)

-Jason
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THE NATIONAL WEATHER SERVICE IN HUNTSVILLE HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  NORTHEASTERN DEKALB COUNTY IN NORTHEAST ALABAMA...

* UNTIL 430 PM CDT

* AT 403 PM CDT...DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM
  CAPABLE OF PRODUCING QUARTER SIZE HAIL AND DAMAGING WINDS IN EXCESS
  OF 60 MPH. THIS STORM WAS LOCATED NEAR RAINSVILLE...AND MOVING
  NORTHEAST AT 45 MPH.

* LOCATIONS IMPACTED INCLUDE...
  FORT PAYNE...RAINSVILLE...VALLEY HEAD...HAMMONDVILLE...MENTONE...
  SHILOH AND PINE RIDGE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF YOU ARE IN THE PATH OF THIS STORM...PREPARE IMMEDIATELY FOR LARGE
HAIL AND DEADLY CLOUD TO GROUND LIGHTNING. PEOPLE OUTSIDE SHOULD MOVE
TO A SHELTER...PREFERABLY INSIDE A STRONG BUILDING AND AWAY FROM
WINDOWS.

Radar at 2:00PM

Radar at 2:00PM

The main threat associated with stronger thunderstorms will be for occasional gusty winds and hail. The tornado threat, although not zero, is very low. This environmental setup is not one conducive for large long-track tornadoes.

We’ll continue to keep you updated as often as necessary, but if you hear a rumble of thunder it is most likely from a garden variety thunderstorm and not of great concern to you.