Spinning… (out of control?)

More than enough weather happening today to keep any Mom, teacher, student, or hard-core enthusiast plenty busy. (I’ll bet the NWSFOs around the region are prepping their severe weather teams, too!) As of 0630EDT, there are watches and warnings of all types — tornado, severe thunderstorms (They go together, don’t they?), high wind, gale, special marine (not USMC!), you name it – across the southeast US.

To set it up, here are some images of some of the current data and forecasts.

The NC DAQ (DENR) profiler shows well the shift in the winds from northeasterly-to-easterly  at the lower levels to west-southwesterly above about 4,500 ft AGL. (Remember this when you read the NWS discussion below.)

 Think about what you’ll be seeing on this morning’s 12Z 850mb analysis: while it may show what one would think would be a warm lower atmosphere (based on the 850mb winds), the layers below 850mb are quite cool.

Ahead of this developing storm, plenty of severe weather reports have already been logged:

The radar imagery is impressive, especially for an early-morning time. (And considering the cool temperatures outside, it sure doesn’t feel like a day with severe weather possible. But remember, look at the data — don’t depend solely on “how it feels.”)

So now we have the analysis, progs, significant weather events, the radar… let’s see what the NWS forecasters are saying about the potential. The Raleigh NWSFO AFD from last night gives a thorough discussion.    (I’m not picking on Raleigh or neglecting others in the region… just a matter of time available to gather and post. Look around at the others — and more current discussions, too.)

RAH AFD 12/0253Z

And finally, here are some of the local airport forecasts (TAFs, terminal aerodrome forecasts) 20080511-1015z-tafs.doc ; if you’ve forgotten the code, you can find it at the NWS Aviation Weather Center web site: http://aviationweather.gov/static/help/taf-decode.php

To follow the developing weather during the day, you can use several web sites. The Storm Prediction Center is a good one: http://www.spc.noaa.gov/. Find their radar depiction links for the big picture or use your local NWS office radar for a display of up-to-the-minute warnings. Here are a few local NWS radar displays from around NC.

Western NC (GSP): http://radar.weather.gov/radar.php?rid=GSP&product=N0R&overlay=11101111&loop=yes

Central NC (RAH): http://radar.weather.gov/radar.php?product=N0R&rid=rax&loop=yes

Coastal NC (MHX): http://radar.weather.gov/radar.php?product=N0R&rid=mhx&loop=yes

From any of these, you can navigate to surrounding areas using the tool in the upper left of the page; or “zoom out” using the links at the bottom of the page.

And finally, if you’re a CoCoRaHS reporter ( http://www.cocorahs.org/ ), don’t forget you can report intense events and especially hail. If you have hail, report it right away so the reports can be used by the forecasters issuing warnings. If you have damaging winds (trees or large limbs down, structural damage or shingles blown off, etc.), report that to your local law enforcement or emergency managers using their non-emergency numbers. Do not use the 911 dispatcher to report weather occurrences!

Great timing! Is that artillery I hear — or thunder?

Been a good-news story lately across the southeast with good rainfall (check the CoCoRaHS maps: http://www.cocorahs.org/), but too much rain is going to inundate the boot heel of Missouri and surrounding region early this week:  take a look at the NWS forecasts for that region.

NWS QPF charts: http://www.hpc.ncep.noaa.gov/qpf/qpf2.shtml

Excessive rainfall guidance: http://www.hpc.ncep.noaa.gov/qpf/excess_rain.shtml  

Then follow the USGS stream flow during the week: http://waterdata.usgs.gov/nwis/rt  

And see how the River Forecast Centers anticipate & respond: http://www.weather.gov/ahps/rfc/rfc.php   

And then watch for the changes as the pattern translates east: http://www.hpc.ncep.noaa.gov/basicwx/day0-7loop.html .

I don’t think it was a weatherman who originated the quote, “Beware the Ides of March!” But this year, especially if you’re in Atlanta, it’s apt.

Here’s a screen shot of the Atlanta (Peachtree City, FFC) radar showing a pretty well-defined hook earlier tonight.

Then, as if to validate the radar, here are the severe weather reports from the Storm Preciction Center (www.spc.noaa.gov):

along with the text version:

Just wondering… are there any NCAA tourney games scheduled in the Georgia Dome? Nice tornado magnet.

So, if you haven’t already walked through your severe weather game plan, it might be time to think about it:

http://www.redcross.org/services/disaster/0,1082,0_591_,00.html

http://www.fema.gov/hazard/tornado/index.shtm

http://www.spc.noaa.gov/faq/tornado/

If you awoke to the news of an earthquake in Indonesia, you can learn more specifics from our streamflow friends at the USGS. They also provide worldwide earthquake monitoring through their aptly named URL, http://earthquake.usgs.gov. Here’s their text for this event:

The following is a release by the United States Geological Survey, National Earthquake Information Center: An earthquake occurred 310 km (195 miles) SSE of Banda Aceh, Sumatra, Indonesia, 310 km (195 miles) WSW of Medan, Sumatra, Indonesia, 335 km (210 miles) WNW of Sibolga, Sumatra, Indonesia, 1545 km (960 miles) NW of JAKARTA, Java, Indonesia at 1:08 AM MST, Feb 20, 2008 (3:08 PM local time in Indonesia). The magnitude and location may be revised when additional data and further analysis results are available. No reports of damage or casualties have been received at this time; however, this earthquake may have caused damage due to its location and size. Earthquakes of this type sometimes cause tsunamis, however the USGS has no information that an actual tsunami has been generated. For information about tsunamis, contact the NOAA Tsunami Warning Centers at http://tsunami.gov.

 If you visit the web page, click on their interactive map (the image here is not “live”), 

and burrow into the data you want to see.  There’s plenty to keep even the hard-core earth scientists happy. From the earthquake that occurred about 2 hours ago, but there’s a lot more on the web site, for example:

For tsunami info (if a tsunami message is issued), visit http://tsunami.gov.    

After seeing the news from the severe weather in the Gulf Coast states (mostly Alabama & Georgia: http://www.spc.noaa.gov/climo/reports/080217_rpts.html), the rainfall we experienced overnight isn’t all that exciting. But recall, we’re in the throes of a significant drought (http://www.ncdrought.org/ or for the latest drought assessment: http://www.erh.noaa.gov/rah/news/content/nws.nc.drought.update.20080208.pdf), so the rain is an important event.
A good soaking is certainly welcome, but where the rains falls is important.  While we had a good heavy rainfall – over 2 inches – in my neighborhood here in Fayetteville, the headwaters of the river basins from which most of NC’s population centers draw their water supplies weren’t so fortunate.

  Refer to the CoCORaHS site  (http://www.cocorahs.org/state.aspx?state=nc) for more specific data.
Most everyone “knows” the conventional wisdom that a drought-busting rainfall event is NOT a two-inch overnight event; what seeps into the ground (and eventually into the rivers) and what runs off matter.  Some environmental critical thinking helps understand this conclusion, but good science requires quantitative support for such a conclusion. Let’s see if we find that.
North Carolina’s rivers (http://www.eenorthcarolina.org/public/ecoaddress/riverbasins/riverbasinmapinteractive.htm) provide the bulk of the state’s water resources. (For more information on water resources in NC, visit DENR’s Division of Water Resources: http://www.ncwater.org/.)  To see the effects of the rain on the various streams’ flow, the U.S. Geological Survey (http://www.usgs.gov/, a part of the Department of the Interior) provides real-time streamflow information across the nation. If we browse to NC’s data and organize the data by river basins (http://waterdata.usgs.gov/nc/nwis/current/?type=flow), we can find the flow data for this rainfall that occurred overnight last night.
From the above CoCoRaHS map of last night’s rainfall across central NC, we know not as much rain fell over the Wake County area as in my gauge in Cumberland County.  So let’s investigate the impact of the rain on a Wake County stream. My favorite Wake County crik is one my brother and I studied (read “played in”) walking to & from grade school: http://waterdata.usgs.gov/nc/nwis/uv?cb_all_00065_00060_00045=on&cb_00065=on&cb_00060=on&format=gif_default&period=7&site_no=0208732534 .  Pigeon House Creek’s rain gauge captured only about a third of an inch, consistent with the other rainfall reports across the county, and the stream flow responded quickly – partly a result of the source (much of the Cameron Village area is paved) and the attributes of the stream & ”basin.”
Meanwhile, on the Cape Fear River downstream of some of the 2- to 3-inch rainfall area, we see the gage height and discharge rising. http://waterdata.usgs.gov/nc/nwis/uv?cb_all_00060_00065_00045=on&cb_00060=on&cb_00065=on&format=gif_default&period=7&site_no=02105500
However, Lake Jordan, the water source for some of the Triangle region that generates some concern for the downstream population on the Cape Fear (for example, this Fayetteville Observer Editorial 18 Feb 2008 – http://www.fayobserver.com/article?id=285881),  didn’t enjoy the benefit of  that 2- to 3-inch rainfall, and the gage is only slowly rising: http://waterdata.usgs.gov/nc/nwis/uv?cb_00065=on&cb_00045=on&format=gif_default&period=7&site_no=02098197.
The rain has now ended

  ; another way to assess the impact of this rainfall event is through the precipitation mapping that the NWS WSR-88D (Doppler radar) displays.

(This image of the radar-derived precipitation since this event began (see the image “CHG: 18 Feb 01:15Z”) is color-contoured according to the scale on the image. Most of the heavier rain fell south and east of Fayetteville and Raleigh. Note that the radar-derived rainfall amounts do not necessarily match the CoCoRaHS-reported amounts. Assessing this difference and adjusting the radar’s precip algorithms  is one of the applications of the CoCORaHS network.)
So we’re spared the serious severe weather, but we don’t get the headwaters’ rainfall needed.  The “so what” of this event is that those of us who enjoyed an overflowing rain gauge can’t become complacent about water usage.  By no means are we out of the drought woods. If you hit the link above and skimmed the most recent drought assessment, you’ll have a better grasp of the scenario.  Don’t like reading?  Here’s a picture from NOAA’s CLimate Prediction Center telling us the next couple or three months are more likely to be warmer (No, not global warming!) and drier than normal: http://www.cpc.noaa.gov/products/predictions/long_range/seasonal.php?lead=2 (The new seasonal outlook should be issued this coming Thursday.)
Again, so what?
While “your” creek may have risen — as did Cross Creek in downtown Fayetteville,

we’re not going to hear our State officials extolling the wonder of this rainfall event, and they should continue to remind us we still need to good stewards of our water (and other) natural resources.

Conditions are ripe for another round of severe weather now brewing in the south central US as shown by the Storm Prediction Center’s (http://www.spc.noaa.gov/) Convective Outlook  this morning. 

 As this storm matures over the next couple of days, it will make an impact all across the eastern US — not a particularly good thing for those traveling in the eastern half of the country this holiday weekend.

But while we tend to focus on our “local” weather, let’s not forget there’s significant weather in other parts of the world. One example is Tropical Cyclone Ivan — that “tropical cyclone” terminology alone tells you it’s not in the west Pacific, where it would be called a “typhoon” or the eastern Atlantic (hurricane), and if you’re thinking, you’ll know this must be a southern (summer) hemisphere storm. Ivan is about to make landfall in Madagascar with winds of 105kt gusting to 130kt. 

Ivan Forecast

So it’s February and there’s a tropical storm in the South Indian Ocean — must be … gasp! … global warming, right?

Probably not.  Remember, Februaury is summer for the southern half of the globe and with a lot of ocean surface, there are tropical storms there, too, in the summer. This graphic show where most storms occur and the forecast centers for the various basins.

   (More information is available from the National Hurricane Center: http://www.nhc.noaa.gov/aboutrsmc.shtml?)

They even plan and have names for them: http://www.nhc.noaa.gov/aboutnames.shtml (scroll to the bottom of the lists). It’s not a big deal.

Unless you’re on the east coast of Madagascar.

Lots going on on the weather map, and the NWS discussion is a readily available resource to understand both what is happening and why. This morning’s (Wednesday 3:30 AM) discussion from Raleigh is here: teachable-moments-nws-discussion.txt, but you can find the daily discussions (updated at least 4X each day) at your local NWS office site. Click on the map to find your local office: http://www.weather.gov/

Beautiful kite-flying weather today; but winds are a little too strong for skydiving methinks.  ( Too windy for this today!)

Here are a few of the 18Z windy observations from across NC < http://www.erh.noaa.gov/rah/current/index.html#obs > :

ASUS42 KRAH 101810
RWRRAH
NORTH CAROLINA WEATHER ROUNDUP
NATIONAL WEATHER SERVICE RALEIGH NC
100 PM EST SUN FEB 10 2008

NOTE: “FAIR” INDICATES FEW OR NO CLOUDS BELOW 12,000 FEET WITH NO SIGNIFICANT WEATHER AND/OR OBSTRUCTIONS TO VISIBILITY.

NCZ001-053-055-056-065-067-111400-

WESTERN NORTH CAROLINA
CITY           SKY/WX    TMP DP  RH WIND       PRES

ASHEVILLE      CLEAR     23   6  48 NW16      30.26R

JEFFERSON      CLEAR     23 -15  18 W10G17    30.16S

MORGANTON      CLEAR     27  10  50 CALM      30.34R

HICKORY        CLEAR     29   5  36 CALM      30.30R

RUTHERFORDTON  CLEAR     28  16  59 CALM      30.30R

MOUNT AIRY     CLEAR     27 -11  18 N5        30.30R

$$
NCZ021-022-025-041-071-084-088-111400-

CENTRAL NORTH CAROLINA
CITY           SKY/WX    TMP DP  RH WIND       PRES

CHARLOTTE      PTCLDY    33   7  33 E13G18    30.32R

GREENSBORO     CLEAR     28  -5  23 N6        30.34R

WINSTON-SALEM  CLEAR     27  -4  26 NE5       30.33R

RALEIGH-DURHAM PTCLDY    29  -3  25 NE6       30.37R

FORT BRAGG     CLEAR     30   5  33 NE3       30.38R

FAYETTEVILLE   CLEAR     33   2  26 NE10      30.38R

$$
NCZ011-015-027-028-043-044-047-080-103-111400-

NORTHEASTERN NORTH CAROLINA
CITY           SKY/WX    TMP DP  RH WIND       PRES

ROANOKE RAPIDS CLEAR     29   0  28 CALM      30.39R

ROCKY MT-WILSO CLEAR     29  -1  27 N9        30.39R

GREENVILLE     SUNNY     30   3  31 CALM      30.39R

ELIZABETH CITY SUNNY     28   5  37 N12       30.39R

MANTEO         NOT AVBL

CAPE HATTERAS  SUNNY     37  16  42 VRB6      30.36R

$$
NCZ078-087-090-091-093-098-101-111400-

SOUTHEASTERN NORTH CAROLINA
CITY           SKY/WX    TMP DP  RH WIND       PRES

LUMBERTON      CLEAR     35   6  29 NE8       30.37R

KINSTON        SUNNY     30   9  40 CALM      30.40R

KENANSVILLE    SUNNY     32   9  37 N5        30.40R

NEW BERN       SUNNY     33   5  30 N6        30.41R

CHERRY POINT   SUNNY     35   4  27 N12       30.40R

BEAUFORT       SUNNY     36   8  31 N9        30.39R

JACKSONVILLE   SUNNY     34   5  29 N8        30.40R

WILMINGTON     SUNNY     35   8  32 NE12      30.38R

$$

Note the low relative humidity (RH) and gusty winds across the state. Notable is the 46kt gusting to 66kts at West Jefferson (”GEV” if you’re using the plot chart; if you’re on the chart, also note usually-windy Boone’s obs at “TNB”). The Ashe County airport (GEV) is on a ridgetop so is well exposed, and its elevation is also a factor in its high-wind reports. If you’re interested in locations and elevations of observation sites, you can see a worldwide list at UCAR’s Real-time Weather Data page < http://www.rap.ucar.edu/weather/surface/ >. (Look for the link to “stations.txt” on the right side of the page. This is a long list (big file — several thousand sites, I think) so it’s helpful to use your toolbar’s “Edit…Find” tools to search for the info you’re after.)

The combination of the low moisture and strong winds prompted the NWS to issue a Red Flag warning for most of central NC. (See the NWS site for current details: http://www.erh.noaa.gov/er/rah/)

RED FLAG WARNING
NATIONAL WEATHER SERVICE RALEIGH NC
352 AM EST SUN FEB 10 2008

…RED FLAG CONDITIONS ARE EXPECTED ACROSS CENTRAL NORTH CAROLINA TODAY…

.WEST WINDS WILL INCREASE TODAY ALONG AND AHEAD OF A COLD FRONT THAT WILL SWEEP THROUGH CENTRAL NORTH CAROLINA. WIND GUSTS COULD REACH UP TO 40 MPH. AS THE DRY AIR FILTERS INTO THE AREA DURING THE DAY… RELATIVE HUMIDITIES WILL DIMINISH TO 15 PERCENT OR LESS BY THE LATE AFTERNOON. THIS WILL DANGEROUS FIRE WEATHER CONDITIONS.

352 AM EST SUN FEB 10 2008

…RED FLAG WARNING REMAINS IN EFFECT FROM 9 AM THIS MORNING TO 9 PM EST THIS EVENING…

WEST WINDS OF 25 MPH…WITH GUSTS UP TO 40 MPH…ARE EXPECTED BY LATE MORNING AND WILL PERSIST THROUGH THE AFTERNOON…THEN SLOWLY DIMINISH THIS EVENING. RELATIVE HUMIDITY VALUES ARE EXPECTED TO DIMINISH TO 15 PERCENT OR LESS THIS AFTERNOON. THESE PARAMETERS ALONG WITH EXTREMELY DRY DEAD TREE AND LEAF LITTER WILL CREATE DANGEROUS WILDFIRE CONDITIONS.

PEOPLE ACROSS CENTRAL NORTH CAROLINA ARE ADVISED NOT TO CONDUCT ANY OUTDOOR BURNING TODAY. IF YOU SPOT A GRASS OR BRUSH FIRE IN YOUR AREA…CALL THE FIRE DEPARTMENT IMMEDIATELY AS CONDITIONS TODAY WILL CAUSE ANY FIRES THAT GET STARTED TO BURN OUT OF CONTROL QUICKLY.

A RED FLAG WARNING MEANS THAT CRITICAL FIRE WEATHER CONDITIONS ARE EITHER OCCURRING NOW…OR WILL SHORTLY. A COMBINATION OF STRONG WINDS…LOW RELATIVE HUMIDITY…AND WARM TEMPERATURES WILL CREATE EXPLOSIVE FIRE GROWTH POTENTIAL.

But there are also other interesting things to look at today, some of which are mentioned in this afternoon’s 12:30PM Area Forecast Discussion from Raleigh: http://www.crh.noaa.gov/product.php?site=NWS&issuedby=RAH&product=AFD&format=CI&version=1&glossary=1&highlight=off

One item is the smoke plume from fires (imagine that!) being visible on the radar. Here’s the Raleigh WSR-88D link:  http://radar.weather.gov/radar.php?rid=rax&product=N0R&overlay=11101111&loop=no

Here’s the 18Z radar image from another radar imagery provider (subscription: www.weathertap.com) that clearly shows the plume. Remember that the radar “sees” targets within its beam that could be precipitation (obviously not today), insects, birds, aircraft or anomalous returns, e.g., the ground under super-refraction scenarios. Some of software in the WSR-88D removes obvious non-weather returns (aircraft). [Click on the graphic below for a nice animatin - you may need to refresh to get it going.]

And now that the Aqua imagery from NASA has been posted (a great near real-time tool:  http://rapidfire.sci.gsfc.nasa.gov/realtime), you’ll have to look hard to find any smoke from these fires in this image, but if your NC geography is pretty good, you’ll be able to spot the airfield at Cherry Point (KNKT) (south of the Neuse River near New Bern) as well as the drop zones on Ft Bragg. And the geologists among us will find the Carolina Bay lakes and other Carolina Bays throughout southeastern NC.  This is a 250-m resolution image. The red squares show satellite identified hot spots (fires), so you can see the fires’ source even if the smoke is too dispersed to see. However, look over toward the coast and find the fire, which I think is from the East Lake dump. This is a big file:  http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?2008041/crefl2_143.A2008041183501-2008041184000.250m.jpg

Recall from the NWS forecast discussion that there’s a cold front — the leading edge of a colder air mass – crossing NC this afternoon and evening.

Consequently, we’ll see the temperatures drop, and a good view of this is shown in the forecasted soundings. Compare the sounding from 12Z this morning (10 Feb)

to the forecasted sounding for tomorrow morning (11 Feb) at the same time.

 It’s easy to see the cooler air over us.

But how it occurs is also interesting as you can see from this sequence of forecasts. Note the infiltration of the cold air over the 24-hour period. 

If you’re adept at thinking in 4-D (3-D plus time), you’ll be able to visualize this frontal passage.

Another way to view this is with a time-height chart showing a cross section of the (forecasted) atmosphere such as this one for Raleigh-Durham (RDU).

A good analyst can “see” (or as Dr. Saucier admonishes…”Visualize!”) the atmosphere in its vertical as well as the horizontal dimension, and these tools help do that.

This Storm Prediction Center mesoscale discussion explains the thinking about the tornadic potential over middle Tennessee. Below the discussion is a copy of the HPX (Fort Campbell WSR-88D) VAD (velocity-azimuth display) winds. As you can see, strong winds aloft with southerly winds in the lowest range gate and SW winds at 10,000 ft will yield a significant storm relative helicity (think “helix,” and refer to the SPC’s acronym list linked in the previous post).
http://www.spc.noaa.gov/products/md/md0168.html
Mesoscale Discussion 168

MESOSCALE DISCUSSION 0168
NWS STORM PREDICTION CENTER NORMAN OK
0659 PM CST TUE FEB 05 2008
AREAS AFFECTED…MIDDLE TN
CONCERNING…SEVERE POTENTIAL…TORNADO WATCH LIKELY 37…
VALID 060059Z - 060230Z
A NEW TORNADO WATCH WILL LIKELY BE NEEDED FOR PORTIONS OF MIDDLE TN.
TORNADIC SUPERCELLS WITH A HISTORY OF DAMAGE PERSIST OVER WRN TN AND NRN MS. THESE CELLS ARE MOVING QUICKLY TO THE NE AT OVER 50 MPH AND WILL MOVE INTO MIDDLE TN.
SOMEWHAT LESS UNSTABLE AIR CURRENTLY RESIDES OVER MIDDLE TN AND POINTS E…WHERE DEWPOINTS WERE IN THE LOWER 60S TO UPPER 50S OVER ERN TN/NRN GA. HOWEVER…A VERY STRONG SWLY LOW LEVEL JET WILL CONTINUE TO TRANSPORT MOISTURE NEWD OUT OF THE LOWER MS VALLEY. 00Z BNA SOUNDING SHOWS A SMALL CAPPING INVERSION NEAR 644 MB BUT WHEN MODIFIED FOR SURFACE OBS UPSTREAM THE PARCELS ARE UNCAPPED.

FURTHER…WIND SHEAR IS EXTREME…WITH HPX VAD WIND PROFILES INDICATING 0-1 SRH OVER 600 M2/S2. GIVEN THESE LEVELS OF SHEAR…INSTABILITY SHOULD BE ENOUGH TO ALLOW STORMS MOVING INTO MIDDLE TN TO REMAIN SEVERE…WITH TORNADO AND HAIL THREAT.

..JEWELL.. 02/06/2008

To keep an eye on the latest thinking for the central North Carolina forecast as this frontal weather approaches us, read the discussions from the Raleigh NWS Forecast Office: http://www.crh.noaa.gov/product.php?site=NWS&issuedby=RAH&product=AFD&format=CI&version=1&glossary=1&highlight=off
Remember, you can monitor the latest severe weather reports via the SPC web site:  http://www.spc.noaa.gov/climo/reports/last3hours.html If you’re using GIS tools in your classroom, the listing of severe reports includes the lat/long, time, and type event, a data set that lends itself to a GIS plotting exercise.

Weather on Tuesday will be a bit rough over much of the lower Mississippi Valley. Here’s the Storm Prediction Center’s “Convective Outlook” for day two (in this case, that’s for Tuesday) and the accompanying discussion from early Monday afternoon with explanatory footnotes added. The most current SPC forecast is here: http://www.spc.noaa.gov/ (If you lived in Tupelo, would your weather radio be ready?)

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1105 AM CST MON FEB 04 2008

VALID 051200Z - 061200Z

…THERE IS A MDT RISK OF SVR TSTMS OVER MUCH OF AR…SERN MO…SRN IL…SRN IN…CENTRAL AND WRN KY…MIDDLE AND WRN TN…PARTS OF NRN AND WRN AL…MUCH OF CENTRAL AND NRN MS…PARTS OF NRN LA……

…THERE IS A SLGT RISK OF SVR TSTMS FROM ERN PORTIONS OF SRN PLAINS INTO THE LOWER AND MID MS AND TN/OH VALLEYS……

…SEVERE THUNDERSTORM OUTBREAK LIKELY OVER LARGE PORTION OF SOUTH CENTRAL U.S. TUESDAY…

THE LARGE TROUGH CURRENTLY WRN U.S. WILL AGGRESSIVELY MOVE FROM SRN/CENTRAL PLAINS TO MID MS VALLEY TUE AS VIGOROUS UPSTREAM SYSTEM ENTERS PAC NW.

AN UNSEASONABLY LARGE WARM SECTOR WILL BE IN PLACE BY EARLY TUESDAY AHEAD OF THE SURFACE LOW DEVELOPING NRN TX AND TO THE S OF FRONTAL ZONE THAT EXTENDS NEWD ACROSS MID MS TO LOWER OH VALLEYS.

WITH 60F DEWPOINTS IN PLACE NWD TO FRONTAL ZONE AS FAR E AS SRN IN/OH AND MID/UPPER 60 DEWPOINTS GULF STATES FROM ERN TX TO AL…THE THERMODYNAMICS WILL SUPPORT SEVERE THUNDERSTORMS OVER A LARGE PORTION OF SOUTH CENTRAL U.S. THRU TUESDAY NIGHT.

MID/UPPER LEVEL JET MAX IN EXCESS OF 100KT ¹ WILL TRACK FROM SRN PLAINS TO LOWER OH/WRN TN VALLEYS BY TUE NIGHT. COUPLED WITH THE LOW LEVEL JET BACKING² AND INCREASING DURING THE AFTERNOON TO 50-60KT LOWER MS/LOWER OH VALLEYS AHEAD OF THE DEVELOPING SURFACE LOW…VERY STRONG/VEERING SHEAR PROFILES DEVELOP…SUPPORTIVE OF SUPERCELLS MUCH OF THE SOUTH CENTRAL U.S.

SEVERE THUNDERSTORMS WILL LIKELY BE ONGOING TUE AM AHEAD OF THE SURFACE LOW ERN OK/NRN TX INTO WRN AR. SEVERE THREAT WILL SPREAD NEWD ACROSS MID MS INTO LOWER OH VALLEY BY AFTERNOON. ADDITIONALLY BY EARLY/MID AFTERNOON SURFACED BASED STORMS³ ARE LIKELY IN THE WARM SECTOR⁴ SPREADING EWD ACROSS LOWER MS/WRN TN VALLEYS.

WITH MLCAPES⁵ AOA 1000 J/KG OVER A LARGE PORTION OF THE WARM SECTOR AND SUCH STRONG SHEAR PROFILES…TORNADIC SUPERCELLS ARE LIKELY BOTH WITH THE SEVERE STORMS AHEAD OF SURFACE LOW/NEAR FRONTAL ZONE AND WITH ANY WARM SECTOR DEVELOPMENT. LONG LIVED SUPERCELLS WILL HAVE POTENTIAL FOR STRONG TORNADOES OVER MUCH OF THE MDT RISK AREA THRU THE EVENING HOURS. SEVERE THUNDERSTORMS WILL CONTINUE THRU TUE NIGHT AND EVOLVE MORE INTO A SQUALL LINE WITH ENHANCED WIND DAMAGE POTENTIAL. HOWEVER TORNADOES WILL BE POSSIBLE WELL AFTER DARK PARTICULARLY IN AREA WHERE HIGHER CAPES ARE AVAILABLE FROM TN SWD.

..HALES.. 02/04/2008

⁵ CAPE is an acronym for Convective Available Potential Energy, a measure of the thermodynamic energy in the atmosphere. The higher the value, the greater the potential of the storm. CAPEs are seasonal: a 1000 J/kg (Joules/kilogram) value this time of year represents a high CAPE; in the summer, with stronger surface heating, a CAPE value of 1000J/kg is not so impressive. For a complete list of acronyms, see http://www.spc.noaa.gov/misc/acronyms.html