Particularly dangerous situation
Encyclopedia
A particularly dangerous situation (PDS) is a type of enhanced wording first used by the National Weather Service
's Storm Prediction Center
in Norman, Oklahoma
on certain severe weather watches. It is issued at the discretion of the forecaster composing the watch and implies that there is an enhanced risk of very severe and life-threatening weather, usually a major tornado outbreak
or (much less often) a long-lived, extreme derecho
event. On April 24, 2011, the National Weather Service
office in Memphis issued the first PDS Flash Flood Watch to highlight the threat for widespread, significant, and potentially life-threatening flash flooding due to repeated rounds of severe thunderstorms.
PDS watches are quite uncommon; less than 3% of watches issued by the SPC from 1996 to 2005 were PDS watches, or an average of 24 each year. There often are multiple PDS watches issued for the same weather system and on the same day during major outbreaks, so the number of days per year that a PDS watch is issued is significantly lower. The first PDS tornado watch was issued by Robert H. Johns
for the April 2, 1982 tornado outbreak across the southern and central Great Plains
.
PDS flash flood watch
es are issued when there is a greater risk of widespread, potentially life-threatening flash flooding. These watches are issued by the local forecast offices, not the Storm Prediction Center.
PDS severe thunderstorm watch
es are issued when there is a greater risk of severe wind damage capable of major structural damage (in addition to large hail and perhaps a few isolated tornadoes), usually due to a strong and persistent derecho. They are very rare (an average of only two each year) as the tornado risk has to remain low enough to only warrant a severe thunderstorm watch (a tornado watch - generally not PDS - would be issued if the tornado risk is significant alongside the extreme wind threat).
PDS tornado watch
es are issued when there is a greater risk of multiple strong, violent or extremely violent tornado
es in the watch area (damage consisting of EF4 or EF5), in addition to significant wind
and hail
damage. While there are no hard criteria for a PDS watch to be issued, they are usually issued when the potential exists for a major tornado outbreak. They represent about 90% of PDS watches issued.
These watches are generally (but not always) issued after a high risk or an upper-end moderate risk of severe storms is issued by the SPC in the convective outlooks.
While historically applied only to Severe Thunderstorm, Tornado, and Flash Flood watches, PDS wording could theoretically be applied to other types of weather watches (i.e., Winter Storm, High Wind, or Fire Weather watches) when an enhanced threat for such conditions exists.
forecast office in Memphis, Tennessee
on April 24, 2011, as mentioned above.
URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
NATIONAL WEATHER SERVICE
MEMPHIS TN
239 PM CDT SUN APR 24 2011
...VERY HEAVY RAINFALL THROUGH THE MIDDLE OF THIS WEEK WILL LIKELY
LEAD TO SIGNIFICANT...WIDESPREAD FLASH FLOODING
...
...THIS IS A PARTICULARLY DANGEROUS SITUATION...
.A BOUNDARY WILL CONTINUE TO REMAIN STATIONARY ACROSS SOUTHERN
MISSOURI
INTO KENTUCKY
THROUGH MONDAY. REPEATED ROUNDS OF
THUNDERSTORMS WILL TRACK ALONG THE FRONT BRINGING HEAVY RAINFALL.
THEN A LOW PRESSURE SYSTEM WILL TRACK ALONG IT INTO MISSOURI AND
PUSH THE FRONT FURTHER SOUTH TO ALONG THE I-40
CORRIDOR MONDAY
NIGHT THROUGH TUESDAY NIGHT. THIS WILL SHIFT THE HEAVY RAIN AXIS
FURTHER SOUTH TO ALONG AND JUST NORTH OF THE I-40 CORRIDOR.
A SECOND LOW PRESSURE SYSTEM WILL TRACK ALONG THE NEWLY STALLED
BOUNDARY AND SET OFF ADDITIONAL TRAINING THUNDERSTORMS LATE
TUESDAY NIGHT AND WEDNESDAY. THE FINAL COLD FRONT WILL PASS
THROUGH LATE WEDNESDAY AFTERNOON...ENDING THE PERSISTENT HEAVY
RAINFALL.
ARZ026>028-035-036-048-049-058-MSZ001>014-TNZ003-004-019>021-
048>055-088>092-250400-
/O.NEW.KMEG.FF.A.0007.110426T0000Z-110428T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CRAIGHEAD-POINSETT-MISSISSIPPI-CROSS-CRITTENDEN-ST. FRANCIS-
LEE AR-PHILLIPS-DESOTO-MARSHALL-BENTON MS-TIPPAH-ALCORN-
TISHOMINGO-TUNICA-TATE-PRENTISS-COAHOMA-QUITMAN-PANOLA-LAFAYETTE-
UNION-WEAKLEY-HENRY-DYER-GIBSON-CARROLL-LAUDERDALE-TIPTON-HAYWOOD-
CROCKETT-MADISON-CHESTER-HENDERSON-DECATUR-SHELBY-FAYETTE-
HARDEMAN-MCNAIRY-HARDIN-
INCLUDING THE CITIES OF...JONESBORO...HARRISBURG...BLYTHEVILLE...
WYNNE...WEST MEMPHIS...FORREST CITY...HELENA...SOUTHAVEN...
OLIVE BRANCH...CORINTH...IUKA...TUNICA...BOONEVILLE...
CLARKSDALE...BATESVILLE...OXFORD...NEW ALBANY...MARTIN...
DRESDEN...PARIS...DYERSBURG...HUMBOLDT...MILAN...HUNTINGDON...
COVINGTON...JACKSON...LEXINGTON...BARTLETT...GERMANTOWN...
COLLIERVILLE...MEMPHIS...MILLINGTON...SOMERVILLE...BOLIVAR...
SAVANNAH
239 PM CDT SUN APR 24 2011
...FLASH FLOOD WATCH IN EFFECT FROM MONDAY EVENING THROUGH
WEDNESDAY EVENING...
THE NATIONAL WEATHER SERVICE IN MEMPHIS
HAS ISSUED A
* FLASH FLOOD WATCH FOR PORTIONS OF EAST ARKANSAS
...NORTH MISSISSIPPI
AND WEST TENNESSEE
...INCLUDING THE FOLLOWING AREAS...IN EAST
ARKANSAS...CRAIGHEAD...CRITTENDEN...CROSS...
LEE...MISSISSIPPI...PHILLIPS...POINSETT AND ST. FRANCIS. IN
NORTH MISSISSIPPI...ALCORN...BENTON...COAHOMA...DESOTO...
LAFAYETTE...MARSHALL...PANOLA...PRENTISS...QUITMAN...TATE...
TIPPAH...TISHOMINGO...TUNICA AND UNION. IN WEST TENNESSEE...
CARROLL...CHESTER...CROCKETT...DECATUR...DYER...FAYETTE...
GIBSON...HARDEMAN...HARDIN...HAYWOOD...HENDERSON...HENRY...
LAUDERDALE...MADISON...MCNAIRY...SHELBY...TIPTON AND WEAKLEY.
* FROM MONDAY EVENING THROUGH WEDNESDAY EVENING.
* THIS IS A PARTICULARLY DANGEROUS SITUATION.
* TOTAL RAINFALL AMOUNTS OF 5 TO 8 INCHES ARE EXPECTED ALONG AND
NORTH OF I-40 WITH 2 TO 5 INCHES EXPECTED SOUTH OF I-40. LOCALLY
HIGHER AMOUNTS ARE LIKELY.
* RAINFALL AMOUNTS SUCH AS THESE MAY LEAD TO WIDESPREAD...
SIGNIFICANT...AND LIFE THREATENING FLASH FLOODING. THIS EVENT
MAY BE AS SEVERE AS THE MAY 1-2 2010 FLOODING
IN PLACES. FLASH
FLOODING OF CITIES...RURAL AREAS...RIVERS...AND SMALL STREAMS
ARE POSSIBLE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.
YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.
&&
$$
ARZ008-009-017-018-MOZ113-115-TNZ001-002-250400-
/O.EXT.KMEG.FF.A.0006.000000T0000Z-110428T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
RANDOLPH-CLAY-LAWRENCE-GREENE-DUNKLIN-PEMISCOT-LAKE-OBION-
INCLUDING THE CITIES OF...WALNUT RIDGE...PARAGOULD...KENNETT...
CARUTHERSVILLE...UNION CITY
239 PM CDT SUN APR 24 2011
...FLASH FLOOD WATCH NOW IN EFFECT THROUGH WEDNESDAY EVENING...
THE FLASH FLOOD WATCH IS NOW IN EFFECT FOR
* PORTIONS OF EAST ARKANSAS...SOUTHEAST MISSOURI AND WEST
TENNESSEE...INCLUDING THE FOLLOWING AREAS...IN EAST ARKANSAS...
CLAY...GREENE...LAWRENCE AND RANDOLPH. IN SOUTHEAST MISSOURI...
DUNKLIN AND PEMISCOT. IN WEST TENNESSEE...LAKE AND OBION.
* THROUGH WEDNESDAY EVENING.
* THIS IS A PARTICULARLY DANGEROUS SITUATION.
* ADDITIONAL RAINFALL AMOUNTS OF 6 TO 9 INCHES ARE EXPECTED.
LOCALLY HIGHER AMOUNTS ARE LIKELY. THIS...IN COMBINATION OF
THE 2 TO 4 INCHES THAT HAVE ALREADY FALLEN MAY LEAD TO TOTAL
RAINFALL AMOUNTS IN EXCESS OF 12 INCHES IN MANY LOCATIONS.
* RAINFALL AMOUNTS SUCH AS THESE WILL LIKELY LEAD TO WIDESPREAD...
SIGNIFICANT...AND LIFE THREATENING FLASH FLOODING. THIS EVENT
MAY BE AS SEVERE AS THE MAY 1-2 2010 FLOODING IN MANY PLACES.
FLASH FLOODING OF CITIES...RURAL AREAS...RIVERS...AND SMALL
STREAMS ARE POSSIBLE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.
YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.
&&
$$
BORGHOFF
NOTE: Blue text indicates links, and the color of all text in the original alert issued was black, except for the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was red in the actual alert.
URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 405
NWS STORM PREDICTION CENTER NORMAN OK
840 PM CDT MON MAY 30 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
PARTS OF NORTHWEST IOWA
PARTS OF CENTRAL KANSAS
MUCH OF EASTERN NEBRASKA
SMALL PART OF SOUTHEASTERN SOUTH DAKOTA
EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 840 PM UNTIL
200 AM CDT.
...THIS IS A PARTICULARLY DANGEROUS SITUATION...
WIDESPREAD DAMAGING WINDS
WIND GUSTS TO 90 MPH LIKELY
SCATTERED LARGE HAIL
ISOLATED HAIL TO 1.5 INCHES IN DIAMETER POSSIBLE
ISOLATED TORNADOES
THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75
STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTHWEST OF
SIOUX CITY IOWA TO 50 MILES SOUTH SOUTHEAST OF RUSSELL KANSAS.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU5).
REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.
OTHER WATCH INFORMATION...CONTINUE...WW 402...WW 403...
DISCUSSION...INTENSE SQUALL LINE HAS DEVELOPED N/S ACROSS CENTRAL
NEB AND CONTINUES TO DEVELOP SWD AS IT MOVES EWD. VERY STRONG PRES
RISE/FALL COUPLET IS DRIVING THE LINE EWD WITH THE FORCING FROM
LARGE SCALE TROUGH ROTATING ACROSS THE NRN/CENTRAL PLAINS PROVIDING
BOTH SHEAR AND UPWARD MOTION TO RESULT IN POTENTIAL FOR VERY
DAMAGING WINDS. IN ADDITION BRIEF TORNADOES ARE STILL POSSIBLE BUT
DAMAGING WINDS NOW ARE THE DOMINANT THREAT.
AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 80
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 23040.
...HALES
in the heart of the extreme tornado outbreak
that killed over 300 people (which clearly verified) as explained above.
NOTE: The blue text in the alert below indicates links; the color of all text in the original alert issued was black, except for the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was red in the actual alert.
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH
NUMBER 235
NWS
STORM PREDICTION CENTER
NORMAN OK
145 PM CDT
WED APR 27 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
MUCH OF ALABAMA
NORTHWEST GEORGIA
SOUTHEAST MISSISSIPPI
SOUTHERN MIDDLE TENNESSEE
EFFECTIVE THIS WEDNESDAY AFTERNOON
AND EVENING
FROM 145 PM UNTIL
1000 PM CDT.
...THIS IS A PARTICULARLY DANGEROUS SITUATION...
DESTRUCTIVE TORNADOES
...LARGE HAIL
TO 4 INCHES IN DIAMETER...
THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING
ARE
POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE
MILES EAST AND WEST OF A LINE FROM 45 MILES NORTHEAST OF
HUNTSVILLE ALABAMA
TO 60 MILES WEST SOUTHWEST OF EVERGREEN
ALABAMA
. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS
.
OTHER WATCH INFORMATION...CONTINUE...WW 230...WW 231...WW
232...WW 233...WW 234...
DISCUSSION...A CLASSIC TORNADO OUTBREAK
SITUATION IS DEVELOPING
ACROSS MUCH OF AL AS DISCRETE TORNADIC SUPERCELLS
FORM OVER MS AND
TRACK ACROSS THE WATCH AREA. STRONG LOW LEVEL AND DEEP LAYER
VERTICAL SHEAR...COMBINED WITH A MOIST AND MODERATELY UNSTABLE AIR
MASS...WILL POSE A DANGEROUS RISK OF STRONG/VIOLENT AND POTENTIALLY
LONG-TRACK TORNADOES.
AVIATION
...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE
AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI
WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 25040.
...HART
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
's Storm Prediction Center
Storm Prediction Center
The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
in Norman, Oklahoma
Norman, Oklahoma
Norman is a city in Cleveland County, Oklahoma, United States, and is located south of downtown Oklahoma City. It is part of the Oklahoma City metropolitan area. As of the 2010 census, Norman was to have 110,925 full-time residents, making it the third-largest city in Oklahoma and the...
on certain severe weather watches. It is issued at the discretion of the forecaster composing the watch and implies that there is an enhanced risk of very severe and life-threatening weather, usually a major tornado outbreak
Tornado outbreak
While there is no single agreed upon definition, generally at least 6-10 tornadoes produced by the same synoptic scale weather system is considered a tornado outbreak. The tornadoes usually occur within the same day, or continue into the early morning hours of the succeeding day, and within the...
or (much less often) a long-lived, extreme derecho
Derecho
A derecho is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms in the form of a squall line usually taking the form of a bow echo...
event. On April 24, 2011, the National Weather Service
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
office in Memphis issued the first PDS Flash Flood Watch to highlight the threat for widespread, significant, and potentially life-threatening flash flooding due to repeated rounds of severe thunderstorms.
PDS watches are quite uncommon; less than 3% of watches issued by the SPC from 1996 to 2005 were PDS watches, or an average of 24 each year. There often are multiple PDS watches issued for the same weather system and on the same day during major outbreaks, so the number of days per year that a PDS watch is issued is significantly lower. The first PDS tornado watch was issued by Robert H. Johns
Robert H. Johns
Bob Johns is an American meteorologist specializing in severe convective storms and tornadoes. Johns spent his career in forecasting and forecaster training. Now retired, he is working on a project reanalyzing the Tri-State Tornado...
for the April 2, 1982 tornado outbreak across the southern and central Great Plains
Great Plains
The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...
.
PDS flash flood watch
Flash flood watch
A Flash flood watch is issued by the National Weather Service when conditions are favorable for flash flooding in flood-prone areas where grounds are already saturated from recent rains....
es are issued when there is a greater risk of widespread, potentially life-threatening flash flooding. These watches are issued by the local forecast offices, not the Storm Prediction Center.
PDS severe thunderstorm watch
Severe thunderstorm watch
[File:Annual_severe_thunderstorm_watch_frequency_in_the_United_States.svg|thumb|right|300px|Map of average annual severe thunderstorm watches in the United States between 1999 and 2008.Legend:...
es are issued when there is a greater risk of severe wind damage capable of major structural damage (in addition to large hail and perhaps a few isolated tornadoes), usually due to a strong and persistent derecho. They are very rare (an average of only two each year) as the tornado risk has to remain low enough to only warrant a severe thunderstorm watch (a tornado watch - generally not PDS - would be issued if the tornado risk is significant alongside the extreme wind threat).
PDS tornado watch
Tornado watch
A tornado watch is issued when conditions are right for a tornado to form. Since any thunderstorm capable of producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch...
es are issued when there is a greater risk of multiple strong, violent or extremely violent tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
es in the watch area (damage consisting of EF4 or EF5), in addition to significant wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
and hail
Hail
Hail is a form of solid precipitation. It consists of balls or irregular lumps of ice, each of which is referred to as a hail stone. Hail stones on Earth consist mostly of water ice and measure between and in diameter, with the larger stones coming from severe thunderstorms...
damage. While there are no hard criteria for a PDS watch to be issued, they are usually issued when the potential exists for a major tornado outbreak. They represent about 90% of PDS watches issued.
These watches are generally (but not always) issued after a high risk or an upper-end moderate risk of severe storms is issued by the SPC in the convective outlooks.
While historically applied only to Severe Thunderstorm, Tornado, and Flash Flood watches, PDS wording could theoretically be applied to other types of weather watches (i.e., Winter Storm, High Wind, or Fire Weather watches) when an enhanced threat for such conditions exists.
Sample PDS Flash Flood Watch
This watch was the first PDS Flash Flood Watch and was issued by the National Weather ServiceNational Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
forecast office in Memphis, Tennessee
Memphis, Tennessee
Memphis is a city in the southwestern corner of the U.S. state of Tennessee, and the county seat of Shelby County. The city is located on the 4th Chickasaw Bluff, south of the confluence of the Wolf and Mississippi rivers....
on April 24, 2011, as mentioned above.
URGENT - IMMEDIATE BROADCAST REQUESTED
FLOOD WATCH
Flood watch
Flood alerts are issued by weather agencies to alert residents that flood conditions are a possibility for their area.-Types of flood alerts:...
NATIONAL WEATHER SERVICE
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
MEMPHIS TN
Memphis, Tennessee
Memphis is a city in the southwestern corner of the U.S. state of Tennessee, and the county seat of Shelby County. The city is located on the 4th Chickasaw Bluff, south of the confluence of the Wolf and Mississippi rivers....
239 PM CDT SUN APR 24 2011
...VERY HEAVY RAINFALL THROUGH THE MIDDLE OF THIS WEEK WILL LIKELY
LEAD TO SIGNIFICANT...WIDESPREAD FLASH FLOODING
Flash flood
A flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields...
...
...THIS IS A PARTICULARLY DANGEROUS SITUATION...
.A BOUNDARY WILL CONTINUE TO REMAIN STATIONARY ACROSS SOUTHERN
MISSOURI
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
INTO KENTUCKY
Kentucky
The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...
THROUGH MONDAY. REPEATED ROUNDS OF
THUNDERSTORMS WILL TRACK ALONG THE FRONT BRINGING HEAVY RAINFALL.
THEN A LOW PRESSURE SYSTEM WILL TRACK ALONG IT INTO MISSOURI AND
PUSH THE FRONT FURTHER SOUTH TO ALONG THE I-40
Interstate 40
Interstate 40 is the third-longest major east–west Interstate Highway in the United States, after I-90 and I-80. Its western end is at Interstate 15 in Barstow, California; its eastern end is at a concurrency of U.S. Route 117 and North Carolina Highway 132 in Wilmington, North Carolina...
CORRIDOR MONDAY
NIGHT THROUGH TUESDAY NIGHT. THIS WILL SHIFT THE HEAVY RAIN AXIS
FURTHER SOUTH TO ALONG AND JUST NORTH OF THE I-40 CORRIDOR.
A SECOND LOW PRESSURE SYSTEM WILL TRACK ALONG THE NEWLY STALLED
BOUNDARY AND SET OFF ADDITIONAL TRAINING THUNDERSTORMS LATE
TUESDAY NIGHT AND WEDNESDAY. THE FINAL COLD FRONT WILL PASS
THROUGH LATE WEDNESDAY AFTERNOON...ENDING THE PERSISTENT HEAVY
RAINFALL.
ARZ026>028-035-036-048-049-058-MSZ001>014-TNZ003-004-019>021-
048>055-088>092-250400-
/O.NEW.KMEG.FF.A.0007.110426T0000Z-110428T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
CRAIGHEAD-POINSETT-MISSISSIPPI-CROSS-CRITTENDEN-ST. FRANCIS-
LEE AR-PHILLIPS-DESOTO-MARSHALL-BENTON MS-TIPPAH-ALCORN-
TISHOMINGO-TUNICA-TATE-PRENTISS-COAHOMA-QUITMAN-PANOLA-LAFAYETTE-
UNION-WEAKLEY-HENRY-DYER-GIBSON-CARROLL-LAUDERDALE-TIPTON-HAYWOOD-
CROCKETT-MADISON-CHESTER-HENDERSON-DECATUR-SHELBY-FAYETTE-
HARDEMAN-MCNAIRY-HARDIN-
INCLUDING THE CITIES OF...JONESBORO...HARRISBURG...BLYTHEVILLE...
WYNNE...WEST MEMPHIS...FORREST CITY...HELENA...SOUTHAVEN...
OLIVE BRANCH...CORINTH...IUKA...TUNICA...BOONEVILLE...
CLARKSDALE...BATESVILLE...OXFORD...NEW ALBANY...MARTIN...
DRESDEN...PARIS...DYERSBURG...HUMBOLDT...MILAN...HUNTINGDON...
COVINGTON...JACKSON...LEXINGTON...BARTLETT...GERMANTOWN...
COLLIERVILLE...MEMPHIS...MILLINGTON...SOMERVILLE...BOLIVAR...
SAVANNAH
239 PM CDT SUN APR 24 2011
...FLASH FLOOD WATCH IN EFFECT FROM MONDAY EVENING THROUGH
WEDNESDAY EVENING...
THE NATIONAL WEATHER SERVICE IN MEMPHIS
Memphis, Tennessee
Memphis is a city in the southwestern corner of the U.S. state of Tennessee, and the county seat of Shelby County. The city is located on the 4th Chickasaw Bluff, south of the confluence of the Wolf and Mississippi rivers....
HAS ISSUED A
* FLASH FLOOD WATCH FOR PORTIONS OF EAST ARKANSAS
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
...NORTH MISSISSIPPI
Mississippi
Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...
AND WEST TENNESSEE
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
...INCLUDING THE FOLLOWING AREAS...IN EAST
ARKANSAS...CRAIGHEAD...CRITTENDEN...CROSS...
LEE...MISSISSIPPI...PHILLIPS...POINSETT AND ST. FRANCIS. IN
NORTH MISSISSIPPI...ALCORN...BENTON...COAHOMA...DESOTO...
LAFAYETTE...MARSHALL...PANOLA...PRENTISS...QUITMAN...TATE...
TIPPAH...TISHOMINGO...TUNICA AND UNION. IN WEST TENNESSEE...
CARROLL...CHESTER...CROCKETT...DECATUR...DYER...FAYETTE...
GIBSON...HARDEMAN...HARDIN...HAYWOOD...HENDERSON...HENRY...
LAUDERDALE...MADISON...MCNAIRY...SHELBY...TIPTON AND WEAKLEY.
* FROM MONDAY EVENING THROUGH WEDNESDAY EVENING.
* THIS IS A PARTICULARLY DANGEROUS SITUATION.
* TOTAL RAINFALL AMOUNTS OF 5 TO 8 INCHES ARE EXPECTED ALONG AND
NORTH OF I-40 WITH 2 TO 5 INCHES EXPECTED SOUTH OF I-40. LOCALLY
HIGHER AMOUNTS ARE LIKELY.
* RAINFALL AMOUNTS SUCH AS THESE MAY LEAD TO WIDESPREAD...
SIGNIFICANT...AND LIFE THREATENING FLASH FLOODING. THIS EVENT
MAY BE AS SEVERE AS THE MAY 1-2 2010 FLOODING
2010 Tennessee floods
The May 2010 Tennessee floods were 1000-year floods in Middle Tennessee, West Tennessee, south-central and western Kentucky and northern Mississippi as the result of torrential rains on May 1 and 2, 2010...
IN PLACES. FLASH
FLOODING OF CITIES...RURAL AREAS...RIVERS...AND SMALL STREAMS
ARE POSSIBLE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.
YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.
&&
$$
ARZ008-009-017-018-MOZ113-115-TNZ001-002-250400-
/O.EXT.KMEG.FF.A.0006.000000T0000Z-110428T0000Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
RANDOLPH-CLAY-LAWRENCE-GREENE-DUNKLIN-PEMISCOT-LAKE-OBION-
INCLUDING THE CITIES OF...WALNUT RIDGE...PARAGOULD...KENNETT...
CARUTHERSVILLE...UNION CITY
239 PM CDT SUN APR 24 2011
...FLASH FLOOD WATCH NOW IN EFFECT THROUGH WEDNESDAY EVENING...
THE FLASH FLOOD WATCH IS NOW IN EFFECT FOR
* PORTIONS OF EAST ARKANSAS...SOUTHEAST MISSOURI AND WEST
TENNESSEE...INCLUDING THE FOLLOWING AREAS...IN EAST ARKANSAS...
CLAY...GREENE...LAWRENCE AND RANDOLPH. IN SOUTHEAST MISSOURI...
DUNKLIN AND PEMISCOT. IN WEST TENNESSEE...LAKE AND OBION.
* THROUGH WEDNESDAY EVENING.
* THIS IS A PARTICULARLY DANGEROUS SITUATION.
* ADDITIONAL RAINFALL AMOUNTS OF 6 TO 9 INCHES ARE EXPECTED.
LOCALLY HIGHER AMOUNTS ARE LIKELY. THIS...IN COMBINATION OF
THE 2 TO 4 INCHES THAT HAVE ALREADY FALLEN MAY LEAD TO TOTAL
RAINFALL AMOUNTS IN EXCESS OF 12 INCHES IN MANY LOCATIONS.
* RAINFALL AMOUNTS SUCH AS THESE WILL LIKELY LEAD TO WIDESPREAD...
SIGNIFICANT...AND LIFE THREATENING FLASH FLOODING. THIS EVENT
MAY BE AS SEVERE AS THE MAY 1-2 2010 FLOODING IN MANY PLACES.
FLASH FLOODING OF CITIES...RURAL AREAS...RIVERS...AND SMALL
STREAMS ARE POSSIBLE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD
TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.
YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION
SHOULD FLASH FLOOD WARNINGS BE ISSUED.
&&
$$
BORGHOFF
Sample PDS Severe Thunderstorm Watch
Although, as mentioned, PDS Severe Thunderstorm Watches are very rare, they are issued when the tornado threat is low and when the forecast wind gusts and hail sizes are very high. This PDS Severe Thunderstorm Watch was from May 30th, 2011:NOTE: Blue text indicates links, and the color of all text in the original alert issued was black, except for the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was red in the actual alert.
URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 405
NWS STORM PREDICTION CENTER NORMAN OK
840 PM CDT MON MAY 30 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
PARTS OF NORTHWEST IOWA
PARTS OF CENTRAL KANSAS
MUCH OF EASTERN NEBRASKA
SMALL PART OF SOUTHEASTERN SOUTH DAKOTA
EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 840 PM UNTIL
200 AM CDT.
...THIS IS A PARTICULARLY DANGEROUS SITUATION...
WIDESPREAD DAMAGING WINDS
WIND GUSTS TO 90 MPH LIKELY
SCATTERED LARGE HAIL
ISOLATED HAIL TO 1.5 INCHES IN DIAMETER POSSIBLE
ISOLATED TORNADOES
THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75
STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTHWEST OF
SIOUX CITY IOWA TO 50 MILES SOUTH SOUTHEAST OF RUSSELL KANSAS.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU5).
REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.
OTHER WATCH INFORMATION...CONTINUE...WW 402...WW 403...
DISCUSSION...INTENSE SQUALL LINE HAS DEVELOPED N/S ACROSS CENTRAL
NEB AND CONTINUES TO DEVELOP SWD AS IT MOVES EWD. VERY STRONG PRES
RISE/FALL COUPLET IS DRIVING THE LINE EWD WITH THE FORCING FROM
LARGE SCALE TROUGH ROTATING ACROSS THE NRN/CENTRAL PLAINS PROVIDING
BOTH SHEAR AND UPWARD MOTION TO RESULT IN POTENTIAL FOR VERY
DAMAGING WINDS. IN ADDITION BRIEF TORNADOES ARE STILL POSSIBLE BUT
DAMAGING WINDS NOW ARE THE DOMINANT THREAT.
AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 80
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
MOTION VECTOR 23040.
...HALES
Sample PDS Tornado Watch
This watch was issued covering AlabamaAlabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
in the heart of the extreme tornado outbreak
April 25–28, 2011 tornado outbreak
An extremely large and violent tornado outbreak, the largest tornado outbreak ever recorded, and popularly known as the 2011 Super Outbreak, occurred from April 25 to 28, 2011. The outbreak affected the Southern, Midwestern, and Northeastern United States, leaving catastrophic destruction in...
that killed over 300 people (which clearly verified) as explained above.
NOTE: The blue text in the alert below indicates links; the color of all text in the original alert issued was black, except for the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was red in the actual alert.
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH
Tornado watch
A tornado watch is issued when conditions are right for a tornado to form. Since any thunderstorm capable of producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch...
NUMBER 235
NWS
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
STORM PREDICTION CENTER
Storm Prediction Center
The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
NORMAN OK
Norman, Oklahoma
Norman is a city in Cleveland County, Oklahoma, United States, and is located south of downtown Oklahoma City. It is part of the Oklahoma City metropolitan area. As of the 2010 census, Norman was to have 110,925 full-time residents, making it the third-largest city in Oklahoma and the...
145 PM CDT
Central Time zone
In North America, the Central Time Zone refers to national time zones which observe standard time by subtracting six hours from UTC , and daylight saving, or summer time by subtracting five hours...
WED APR 27 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
MUCH OF ALABAMA
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
NORTHWEST GEORGIA
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
SOUTHEAST MISSISSIPPI
Mississippi
Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...
SOUTHERN MIDDLE TENNESSEE
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
EFFECTIVE THIS WEDNESDAY AFTERNOON
Afternoon
Afternoon is the time of day from noon to about 18:00.The term should not be confused with "after noon" , which is a translation of the Latin "post meridiem" as used in the 12-hour clock, meaning a time of day from noon to midnight.In Australia and New Zealand, the word "arvo" is a slang term for...
AND EVENING
Evening
Evening is the period between the late afternoon and night when daylight is decreasing, around dinner time at 6pm. Though the term is subjective, evening is typically understood to begin before sunset, during the close of the standard business day and extend until nightfall, the beginning of night...
FROM 145 PM UNTIL
1000 PM CDT.
...THIS IS A PARTICULARLY DANGEROUS SITUATION...
DESTRUCTIVE TORNADOES
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
...LARGE HAIL
Hail
Hail is a form of solid precipitation. It consists of balls or irregular lumps of ice, each of which is referred to as a hail stone. Hail stones on Earth consist mostly of water ice and measure between and in diameter, with the larger stones coming from severe thunderstorms...
TO 4 INCHES IN DIAMETER...
THUNDERSTORM WIND GUSTS
Downburst
A downburst is created by an area of significantly rain-cooled air that, after reaching ground level, spreads out in all directions producing strong winds. Unlike winds in a tornado, winds in a downburst are directed outwards from the point where it hits land or water...
TO 80 MPH...AND DANGEROUS LIGHTNING
Lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
ARE
POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE
MILES EAST AND WEST OF A LINE FROM 45 MILES NORTHEAST OF
HUNTSVILLE ALABAMA
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....
TO 60 MILES WEST SOUTHWEST OF EVERGREEN
ALABAMA
Evergreen, Alabama
Evergreen is a city in Conecuh County, Alabama, United States. As of the 2010 census the population was 3,944. The city is the county seat of Conecuh County.-History:Early settlers to the area came from Georgia and South Carolina beginning in 1818...
. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS
Tornado warning
A tornado warning is an alert issued by government weather services to warn that severe thunderstorms with tornadoes may be imminent. It can be issued after a tornado or funnel cloud has been spotted by eye, or more commonly if there are radar indications of tornado formation...
.
OTHER WATCH INFORMATION...CONTINUE...WW 230...WW 231...WW
232...WW 233...WW 234...
DISCUSSION...A CLASSIC TORNADO OUTBREAK
Tornado outbreak
While there is no single agreed upon definition, generally at least 6-10 tornadoes produced by the same synoptic scale weather system is considered a tornado outbreak. The tornadoes usually occur within the same day, or continue into the early morning hours of the succeeding day, and within the...
SITUATION IS DEVELOPING
ACROSS MUCH OF AL AS DISCRETE TORNADIC SUPERCELLS
Supercell
A supercell is a thunderstorm that is characterized by the presence of a mesocyclone: a deep, continuously-rotating updraft. For this reason, these storms are sometimes referred to as rotating thunderstorms...
FORM OVER MS AND
TRACK ACROSS THE WATCH AREA. STRONG LOW LEVEL AND DEEP LAYER
VERTICAL SHEAR...COMBINED WITH A MOIST AND MODERATELY UNSTABLE AIR
MASS...WILL POSE A DANGEROUS RISK OF STRONG/VIOLENT AND POTENTIALLY
LONG-TRACK TORNADOES.
AVIATION
Aviation
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...
...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI
Cumulonimbus cloud
Cumulonimbus is a towering vertical cloud that is very tall, dense, and involved in thunderstorms and other inclement weather. Cumulonimbus originates from Latin: Cumulus "Heap" and nimbus "rain". It is a result of atmospheric instability. These clouds can form alone, in clusters, or along a cold...
WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 25040.
...HART