Particularly Dangerous Situation

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A Particularly Dangerous Situation (PDS) is a type of enhanced wording first used by the Storm Prediction Center (SPC), a national guidance center of the United States National Weather Service, for tornado watches and eventually expanded to use for other severe weather watches and warnings. It is issued at the discretion of the forecaster composing the watch or warning 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, but possibly another weather hazard such as an exceptional flash flood.[1]

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.[2] When a PDS watch is issued, there are often more PDS watches issued for the same weather system, even on the same day during major outbreaks, so the number of days per year that a PDS watch is issued is significantly lower.

Background[edit]

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.[3] While historically applied only to severe thunderstorm, tornado and flash flood watches (i.e., Severe Local Storm "polygonal" events), PDS wording could theoretically be applied to other types of weather watches (such as winter storm, high wind, hurricane, or fire weather watches) when an enhanced threat for such conditions exists. These watches have generally (but not always) been issued during a high risk or an upper-end moderate risk either of severe storms from the SPC's convective outlooks or of flash flooding from the Weather Prediction Center (WPC)'s Excessive Rainfall Outlooks.

On April 24, 2011, the National Weather Service Weather Forecast Office in Memphis, Tennessee 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.

Issuance[edit]

PDS Tornado Watch[edit]

PDS tornado watches are issued when there is a higher than normal risk of multiple strong to violent tornadoes – especially those that are predicted to be long-track in nature, with path lengths of more than 20 miles – in the watch area (usually amounting to damage consistent with EF4 or EF5 tornadoes at maximum), in addition to including significant wind and hail damage. This enhanced wording in a Tornado Watch is meant to alert the public of the potential for very life-threatening severe weather. While there are no set criteria for a PDS watch to be issued, they are usually issued when the potential exists for a major tornado outbreak. These types of tornado watches represent about 90% of PDS watches issued by the Storm Prediction Center. PDS Tornado Watches are often issued on high risk days for severe weather.[2]

The PDS Tornado Watch shown below was issued covering Alabama during the early stages of the 2011 Super Outbreak that killed over 300 people (which clearly verified) as explained above.

NOTE: The color of all text in the original alert issued was black, except for the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was rendered in red (not bolded) in the actual alert.[4]

Particularly Dangerous Situation (PDS) Tornado Watch 235
SEL5

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

The most recent PDS Tornado Watch was issued on June 12, 2017 (Tornado Watch 317).

PDS Severe Thunderstorm Watch[edit]

PDS severe thunderstorm watches are issued when there is a higher than normal risk of severe thunderstorm winds capable of major structural damage (in addition to large hail and perhaps a few isolated tornadoes), usually due to a strong and persistent derecho. These watches are very rare (accounting an average of only two each year), as the risk for tornadoes must remain low enough to not warrant a tornado watch (a normal tornado watch would be issued if the tornado risk is significant alongside the extreme wind threat).[2]

This PDS Severe Thunderstorm Watch shown below was the most recent from May 27, 2017:

NOTE: 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 (not bolded) in the actual alert.[5]

Particularly Dangerous Situation (PDS) Severe Thunderstorm Watch 280

SEL5

SEL0

  URGENT - IMMEDIATE BROADCAST REQUESTED
  Severe Thunderstorm Watch Number 280
  NWS Storm Prediction Center Norman OK
  515 PM CDT Sat May 27 2017
  The NWS Storm Prediction Center has issued a
  * Severe Thunderstorm Watch for portions of 
    Southern Illinois
    Southwest Indiana
    Western and south-central Kentucky
    Far southeast Missouri
    Western and middle Tennessee
  * Effective this Saturday afternoon from 515 PM until Midnight
    CDT.
  ...THIS IS A PARTICULARLY DANGEROUS SITUATION...
  * Primary threats include...
    Widespread damaging winds expected with scattered significant
      gusts to 80 mph likely
    Scattered large hail and isolated very large hail events to 2
      inches in diameter possible
    A few tornadoes possible
  SUMMARY...A very fast-moving line of convection will continue to
  pose a risk for widespread wind damage as it races
  east-southeastward through the evening hours. A few tornadoes and
  hail will also be possible with the fast-moving squall line and/or
  other line-preceding storms.
  The severe thunderstorm watch area is approximately along and 70
  statute miles north and south of a line from 30 miles west northwest
  of Cape Girardeau MO to 55 miles east southeast of Bowling Green KY.
  For a complete depiction of the watch see the associated watch
  outline update (WOUS64 KWNS WOU0).
  PRECAUTIONARY/PREPAREDNESS ACTIONS...
  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 275...WW 276...WW
  277...WW 278...WW 279...
  AVIATION...A few severe thunderstorms with hail surface and aloft to
  2 inches. Extreme turbulence and surface wind gusts to 70 knots. A
  few cumulonimbi with maximum tops to 600. Mean storm motion vector
  29045.
  ...Guyer

PDS Flash Flood Watch[edit]

PDS Flash Flood Watches are issued when there is a higher than normal risk of widespread, life-threatening flash flooding. These watches are issued by local NWS Weather Forecast Offices, not the Storm Prediction Center.

This watch shown here, was the first PDS Flash Flood Watch and was issued by the National Weather Service Forecast Office in Memphis, Tennessee on April 24, 2011, as mentioned above.[6]

NOTE: The color of all text in the original alert issued was black, including the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was neither rendered in red nor bolded in the actual alert.

Particularly Dangerous Situation (PDS) Flood Watch

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

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

PDS Flash Flood Warning[edit]

PDS Flash Flood Warnings are issued when there is a higher than normal risk of widespread, life-threatening flash flooding. Like PDS Flash Flood Watches, they are issued by the local NWS Weather Forecast Offices, rather than the Storm Prediction Center. Recently, they have been issued as PDS Flash Flood Emergencies, most notably by the National Weather Service offices in Houston, TX and Corpus Christi, TX.

This warning was issued in the early afternoon hours of August 27, 2017 by the National Weather Service Forecast Office in Houston/Galveston, Texas while Tropical Storm Harvey was affecting the area. It also contains the Flash Flood Emergency phrase, which further underscores the risk of life-threatening flash flooding.[7]

NOTE: The color of all text in the original alert issued was black, including the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was neither rendered in red nor bolded in the actual alert.

Particularly Dangerous Situation (PDS) Flash Flood Warning

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Houston/Galveston TX
126 PM CDT SUN AUG 27 2017

...FLASH FLOOD EMERGENCY FOR LIFE-THREATENING CATASTROPHIC FLOODING...

The National Weather Service in League City has issued a

  • Flash Flood Warning for...

Northeastern Austin County in southeastern Texas...
Southeastern Grimes County in southeastern Texas...
Southeastern Washington County in southeastern Texas...
Galveston County in southeastern Texas...
Southern Montgomery County in southeastern Texas...
Central Fort Bend County in southeastern Texas...
Northeastern Brazoria County in southeastern Texas...
Western Chambers County in southeastern Texas...
Waller County in southeastern Texas...
West central Liberty County in southeastern Texas...
Harris County in southeastern Texas...

  • Until 715 PM CDT.


  • At 119 PM CDT, Doppler radar indicated continued bands on rain and

thunderstorms across the area. Water rescues are ongoing and
widespread flooding will continue, and perhaps worsen at some
locations. Historic flooding is expected to continue in the
Houston metropolitan area through the foreseeable future.

This is a FLASH FLOOD EMERGENCY FOR LIFE-THREATENING CATASTROPHIC
FLOODING. This is a PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER
GROUND NOW!

  • Some locations that will experience flooding include...

Pasadena, Pearland, League City, Sugar Land, Baytown, Missouri
City, Galveston Island West End, Galveston Causeway, Texas City,
Friendswood, La Porte, Deer Park, Rosenberg, Alvin, northwestern
Angleton, Dickinson, Stafford, South Houston, Bellaire and Humble.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to higher ground now. This is an extremely dangerous and
life-threatening situation. Do not attempt to travel unless you are
fleeing an area subject to flooding or under an evacuation order.

PDS Tornado Warning[edit]

PDS tornado warnings are currently issued on an experimental basis by the 38 National Weather Service Weather Forecast Offices within the Central Region.[8] The criteria for a PDS warning is when a tornado on the ground has been spotted or confirmed, or a significant tornado is expected (due to radar signatures). While the intention of this experimental warning may be to replace the loosely defined tornado emergency, PDS tornado warnings are structured as the second highest level of tornado warning within the Impact Based Warning system (an experiment – which also includes tags within warning products illustrating radar indications or physical observations of tornadoes, and damage potential – participated by the 33 Weather Forecast Offices within the Central Region, as well as eight additional offices within the Western, Eastern and Southern regions that began utilizing the system in the spring of 2014[9]); a tornado emergency, the highest warning level, is used within the United States for destructive tornadoes approaching more densely populated areas. These are the first warnings issued with PDS wording, and like PDS flash flood watches, are issued by local forecast offices.[10][11] The tornado warning below was issued for northwestern Greenville and Pickens counties in South Carolina in early October 2017, when the remnants of Hurricane Nate impacting the Southeast produced multiple tornadic storm cells. The warning was upgraded to a PDS tornado warning via a Severe Weather Statement bulletin. PDS tornado warnings are relatively uncommon in the immediate area given the mountainous terrain along the northwest border of South Carolina.

NOTE: The color of all text in the original alert issued was black, including the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was neither rendered in red nor bolded in the actual alert.[12]

Particularly Dangerous Situation (PDS) Tornado Warning

717 WWUS52 KGSP 082041
SVSGSP

Severe Weather Statement
National Weather Service Greenville-Spartanburg SC
441 PM EDT SUN OCT 8 2017

SCC045-077-082115-
/O.CON.KGSP.TO.W.0022.000000T0000Z-171008T2115Z/
Greenville SC-Pickens SC-
441 PM EDT SUN OCT 8 2017

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 515 PM EDT FOR
NORTHWESTERN GREENVILLE AND PICKENS COUNTIES...

At 440 PM EDT, a confirmed large and extremely dangerous tornado was
located 5 miles southwest of Pickens, or near Norris, moving north at
35 mph.

This is a PARTICULARLY DANGEROUS SITUATION. TAKE COVER NOW!

HAZARD...Damaging tornado.

SOURCE...Radar confirmed tornado.

IMPACT...You are in a life-threatening situation. Flying debris may
be deadly to those caught without shelter. Mobile homes
will be destroyed. Considerable damage to homes,
businesses, and vehicles is likely and complete destruction
is possible.

The tornado will be near...
Table Rock State Park and Caesars Head State Park around 510 PM
EDT.

Other locations impacted by this dangerous storm include Sunset,
Pumpkintown, Sassafras Mountain, Nine Times and Cleveland.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To repeat, a large, extremely dangerous and potentially deadly
tornado is on the ground. To protect your life, TAKE COVER NOW! Move
to a basement or an interior room on the lowest floor of a sturdy
building. Avoid windows. If you are outdoors, in a mobile home, or in
a vehicle, move to the closest substantial shelter and protect
yourself from flying debris.

Heavy rainfall may hide this tornado. Do not wait to see or hear the
tornado. TAKE COVER NOW!

Please report damaging winds, hail, or flooding to the National
Weather Service Greenville-Spartanburg by calling toll free, 1, 800,
2 6 7, 8 1 0 1, or by posting on our Facebook page, or Tweet it using
hashtag nwsgsp. Your message should describe the event and the
specific location where it occurred.

&&

LAT...LON 3468 8285 3470 8285 3470 8286 3473 8285
3474 8288 3508 8282 3509 8279 3507 8278
3507 8275 3508 8275 3510 8269 3513 8268
3512 8266 3513 8264 3513 8263 3515 8257
3516 8255 3516 8248 3475 8263 3467 8279
TIME...MOT...LOC 2040Z 192DEG 32KT 3481 8276

TORNADO...OBSERVED
TORNADO DAMAGE THREAT...CONSIDERABLE
HAIL...<.75IN

$$

08

PDS Wind Chill Warning[edit]

PDS wind chill warnings are issued when there is an enhanced risk of frost bite, hypothermia, and eventually death due to extremely low wind chills. These warnings are issued by the National Weather Service Weather Forecast Offices rather than the Storm Prediction Center.

The PDS Wind Chill Warning shown below was issued by the National Weather Service in the Twin Cities on January 5, 2014.

NOTE: The color of all text in the original alert issued was black, except for the text "THIS IS A PARTICULARLY DANGEROUS SITUATION", which was neither rendered in red nor bolded in the actual alert.[13]

Particularly Dangerous Situation (PDS) Winter Weather Message

629
WWUS43 KMPX 050957
WSWMPX

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
357 AM CST SUN JAN 5 2014

...HISTORIC AND LIFE-THREATENING COLD AIR HAS ARRIVED...
...THIS IS A PARTICULARLY DANGEROUS SITUATION...

.THE COLDEST AIRMASS SINCE 1996 CONTINUES TO MOVE SOUTHEAST OUT
OF CANADA AND INTO MINNESOTA AND WISCONSIN. WIND CHILL VALUES WILL
RANGE BETWEEN 30 AND 45 BELOW TODAY AND CONTINUE TO FALL THROUGH
MONDAY MORNING. AIR TEMPERATURES TONIGHT WILL DROP INTO THE 20S
AND 30S BELOW ZERO. GUSTY WEST OR NORTHWEST WINDS COMBINED WITH
THESE EXTREMELY COLD TEMPERATURES WILL PRODUCE WIND CHILLS OF 50
TO 65 BELOW ZERO LATE TONIGHT AND EARLY MONDAY.

WIND CHILLS COLDER THAN 50 BELOW CAN CAUSE EXPOSED FLESH TO
FREEZE IN ONLY 5 MINUTES. A WIND CHILL WARNING IS IN EFFECT FOR
CENTRAL AND SOUTHERN MINNESOTA AND WEST CENTRAL WISCONSIN THROUGH
NOON TUESDAY.

THE GUSTY WINDS WILL ALSO BRING AREAS OF BLOWING SNOW TO MUCH OF
THE AREA TODAY AND TONIGHT. WHERE GUSTS REACH 35 TO 45 MPH OVER
WESTERN AND SOUTHERN MINNESOTA...VISIBILITIES MAY OCCASIONALLY BE
REDUCED TO LESS THAN A HALF MILE IN NEAR BLIZZARD CONDITIONS. THIS
WILL BRING AN ADDITIONAL LEVEL OF DANGER TO ANYONE STRANDED.

MNZ041-047-048-054>057-064-065-067-073>075-082>085-091>093-052115-
/O.CON.KMPX.WC.W.0001.000000T0000Z-140107T1800Z/
DOUGLAS-STEVENS-POPE-LAC QUI PARLE-SWIFT-CHIPPEWA-KANDIYOHI-
YELLOW MEDICINE-RENVILLE-SIBLEY-REDWOOD-BROWN-NICOLLET-WATONWAN-
BLUE EARTH-WASECA-STEELE-MARTIN-FARIBAULT-FREEBORN-
INCLUDING THE CITIES OF...ALEXANDRIA...MORRIS...GLENWOOD...
MADISON...BENSON...MONTEVIDEO...WILLMAR...GRANITE FALLS...
OLIVIA...GAYLORD...REDWOOD FALLS...NEW ULM...ST. PETER...
ST. JAMES...MANKATO...WASECA...OWATONNA...FAIRMONT...BLUE EARTH...
ALBERT LEA
357 AM CST SUN JAN 5 2014

...WIND CHILL WARNING REMAINS IN EFFECT UNTIL NOON CST TUESDAY...

A WIND CHILL WARNING REMAINS IN EFFECT UNTIL NOON CST TUESDAY.

  • THIS IS A PARTICULARLY DANGEROUS SITUATION!
  • WIND CHILL VALUES: 35 TO 65 BELOW...WITH THE COLDEST READINGS

TONIGHT AND MONDAY MORNING.

  • IMPACTS: EXPOSED FLESH WILL FREEZE IN 10 MINUTES WITH WIND

CHILLS OF 35 BELOW...AND IN 5 MINUTES WITH WIND CHILLS OF 50 BELOW OR COLDER.

  • OTHER IMPACTS...WINDS GUSTING BETWEEN 35 AND 45 MPH THIS

AFTERNOON AND TONIGHT WILL LEAD TO BLOWING SNOW WITH
VISIBILITIES OCCASIONALLY DROPPING TO 1/2 MILE OR LESS IN NEAR
BLIZZARD CONDITIONS. SHOULD YOUR VEHICLE BECOME STRANDED...YOUR
LIFE WILL BE AT RISK. CONSIDER POSTPONING ALL TRAVEL.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL WARNING MEANS THE COMBINATION OF VERY COLD AIR AND
STRONG WINDS WILL CREATE DANGEROUSLY LOW WIND CHILL VALUES. THIS
WILL RESULT IN FROST BITE AND LEAD TO HYPOTHERMIA OR DEATH IF
PRECAUTIONS ARE NOT TAKEN.

&&

$$

MNZ042>045-049>053-058>063-066-068>070-076>078-WIZ014>016-023>028-
052115-
/O.CON.KMPX.WC.W.0001.000000T0000Z-140107T1800Z/
TODD-MORRISON-MILLE LACS-KANABEC-STEARNS-BENTON-SHERBURNE-ISANTI-
CHISAGO-MEEKER-WRIGHT-HENNEPIN-ANOKA-RAMSEY-WASHINGTON-MCLEOD-
CARVER-SCOTT-DAKOTA-LE SUEUR-RICE-GOODHUE-POLK-BARRON-RUSK-
ST. CROIX-PIERCE-DUNN-PEPIN-CHIPPEWA-EAU CLAIRE-
INCLUDING THE CITIES OF...LONG PRAIRIE...LITTLE FALLS...
PRINCETON...MORA...ST. CLOUD...FOLEY...ELK RIVER...CAMBRIDGE...
CENTER CITY...LITCHFIELD...MONTICELLO...MINNEAPOLIS...BLAINE...
ST. PAUL...STILLWATER...HUTCHINSON...CHASKA...SHAKOPEE...
BURNSVILLE...LE SUEUR...FARIBAULT...RED WING...AMERY...
BALSAM LAKE...RICE LAKE...BARRON...LADYSMITH...HUDSON...
NEW RICHMOND...RIVER FALLS...PRESCOTT...MENOMONIE...BOYCEVILLE...
DURAND...PEPIN...CHIPPEWA FALLS...BLOOMER...EAU CLAIRE...ALTOONA
357 AM CST SUN JAN 5 2014

...WIND CHILL WARNING REMAINS IN EFFECT UNTIL NOON CST TUESDAY...

A WIND CHILL WARNING REMAINS IN EFFECT UNTIL NOON CST TUESDAY.

  • THIS IS A PARTICULARLY DANGEROUS SITUATION!
  • WIND CHILL VALUES: 35 TO 65 BELOW...WITH THE COLDEST READINGS

TONIGHT AND MONDAY MORNING.

  • IMPACTS: EXPOSED FLESH WILL FREEZE IN 10 MINUTES WITH WIND

CHILLS OF 35 BELOW...AND IN 5 MINUTES WITH WIND CHILLS OF 50
BELOW OR COLDER.

  • OTHER IMPACTS...AREAS OF BLOWING SNOW ARE POSSIBLE AS WINDS GUST

AS HIGH AS 35 MPH THIS AFTERNOON AND TONIGHT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL WARNING MEANS THE COMBINATION OF VERY COLD AIR AND
STRONG WINDS WILL CREATE DANGEROUSLY LOW WIND CHILL VALUES. THIS
WILL RESULT IN FROST BITE AND LEAD TO HYPOTHERMIA OR DEATH IF
PRECAUTIONS ARE NOT TAKEN.

&&

$$

BORGHOFF


PDS Special Weather Statement[edit]

A special weather statement (SWS) is usually issued by the NWS for hazards that have not yet reached warning or advisory status or that do not have a specific code of their own.

The PDS Special Weather Statement below was issued by the National Weather Service in Buffalo, New York on December 11, 2013, regarding extreme amounts of lake effect snow to impact the defined area.

Particularly Dangerous Situation (PDS) Special Weather Statement
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BUFFALO NY
255 PM EST WED DEC 11 2013

NYZ006>008-112200-
OSWEGO-JEFFERSON-LEWIS-
INCLUDING THE CITIES OF...OSWEGO...WATERTOWN...LOWVILLE
255 PM EST WED DEC 11 2013

...EXTREMELY HEAVY LAKE EFFECT SNOW TO CONTINUE THROUGH THE
EVENING COMMUTE...

A BAND OF VERY INTENSE LAKE EFFECT SNOW EXTENDING FROM BETWEEN
SANDY CREEK AND ADAMS ALONG I-81...EASTWARD TO LOWVILLE AND
CROGHAN WILL CONTINUE THROUGH THE AFTERNOON. OTHER AREAS IMPACTED
BY THIS SNOW BAND INCLUDE BUT ARE NOT LIMITED TO
MONTAGUE...MARTINSBURG...HIGHMARKET...TURIN...SANDY
CREEK...LACONA...PULASKI...LOWVILLE AND LYONS FALLS. THIS BAND
WILL DRIFT SLIGHTLY NORTH OVER THE NEXT COUPLE OF HOURS. SNOWFALL
RATES OF 3 TO 5 INCHES PER HOUR CAN BE EXPECTED WITHIN THE MOST
INTENSE LAKE BANDS. IN ADDITION...WEST WINDS BETWEEN 15 TO 30 MPH
WILL RESULT IN CONSIDERABLE BLOWING AND DRIFTING SNOW...REDUCING
VISIBILITIES TO NEAR ZERO AT TIMES MAKING FOR WHITE OUT
CONDITIONS.

...THIS IS A PARTICULARLY DANGEROUS SITUATION...

THIS WILL PRODUCE TREACHEROUS TRAVEL CONDITIONS ACROSS THE TUG
HILL...INTERSTATE 81 FROM PULASKI TO ADAMS...AND ALONG STATE
ROUTE 12 FROM TURIN TO LOWVILLE. TRAVEL ACROSS THESE AREAS WILL
BE NEARLY IMPOSSIBLE THIS AFTERNOON...AND IS HIGHLY DISCOURAGED.

$$

JAM

PDS Red Flag Warning[edit]

PDS Red Flag Warning (Reno, NV) - December 19th, 2017
URGENT - FIRE WEATHER MESSAGE
National Weather Service Reno NV
140 PM PST Tue Dec 19 2017

CAZ273-201500-
/O.CON.KREV.FW.W.0017.171220T0300Z-171221T0300Z/
Mono and Eastern Alpine Counties-
140 PM PST Tue Dec 19 2017

...RED FLAG WARNING REMAINS IN EFFECT FROM 7 PM THIS EVENING TO
7 PM PST WEDNESDAY FOR GUSTY WINDS AND LOW HUMIDITY FOR MONO
COUNTY SOUTH OF MONO LAKE...

'''This is a Particularly Dangerous Situation.'''

AFFECTED AREA...Fire Zone 273 Mono and Eastern Alpine Counties.

Winds...Southwest 25 to 40 mph with gusts up to 70 mph late
tonight into Wednesday morning. The winds will shift to the
north by early Wednesday afternoon with speeds of 20 to 30 mph
and gusts to 55 mph.

Location and timing of strongest wind gusts...The strongest
wind gusts will be along the 395 corridor tonight into
Wednesday morning. Wednesday afternoon the strongest gusts
will be in the Owens and Chalfant Valleys.

Humidity...As low as 10 to 20% tonight and again late
Wednesday afternoon. Brief recovery near or above 50% is
possible late Wednesday morning.

Duration...10 to 15 hours, locally up to 20 hours.

Impacts...The combination of gusty winds and low humidity can
cause fire to rapidly grow in size and intensity.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This is a particularly dangerous situation with low humidity and
very high winds. New fires will grow rapidly out of control, in
some cases people may not be able to evacuate safely in time
should a fire approach. Avoid outdoor activities that can cause a
spark near dry vegetation, such as yard work, target shooting, or
campfires. Follow local fire restrictions. Check weather.gov/reno
for updates and livingwithfire.info for preparedness tips.

Other watches and warnings[edit]

While the use of PDS wording for other types of watches and warnings has not been used, PDS wording could theoretically be applied to any kind of watch or warning to alert the public to weather events where there exists an increased risk of loss of life or widespread damage to property. Such situations could include PDS watches or warnings for blizzards, ice storms, high winds, extreme heat, or fire danger. For example, on October 29, 2012 in advance of Hurricane Sandy, which was expected to become post-tropical prior to making landfall, a high wind warning was issued for New Jersey stating "THIS IS AN EXTREMELY DANGEROUS SITUATION!".[14] Similarly, on May 26, 2015 during the flood disaster in Texas, Oklahoma, Arkansas, and Louisiana, a flood warning was issued similar to a PDS flood warning stating "...THIS IS A DANGEROUS AND LIFE-THREATENING SITUATION...".[15] A severe thunderstorm warning bulletin issued by the National Weather Service at Tampa Bay/Ruskin regarding a strong, tornadic storm system moving through the area contained the following: "THIS STORM MAY CAUSE SERIOUS INJURY AND SIGNIFICANT PROPERTY DAMAGE.".[16]

References[edit]

  1. ^ NOAA (2004-04-18). "Storm Prediction Center Frequently Asked Questions (FAQ)". Retrieved 2008-05-23. 
  2. ^ a b c Dean, Andrew R. (2006-11-07). "PDS watches: how dangerous are these "particularly dangerous situations?" (2006 - 23SLS_23sls)". American Meteorological Society. Retrieved 2008-05-23. 
  3. ^ Lewis, John (2007-11-03). "A Forecaster's Story: Robert H. Johns". Electronic Journal of Severe Storms Meteorology. 2 (7). 
  4. ^ NOAA (2011-04-27). "Storm Prediction Center: Particularly Dangerous Situation (PDS) Tornado Watch 235". Retrieved 2011-04-27. 
  5. ^ NOAA (2017-05-27). "Storm Prediction Center: Particularly Dangerous Situation (PDS) Severe Thunderstorm Watch 280". 
  6. ^ "IEM Valid Time Extent Code (VTEC) App". Mesonet.agron.iastate.edu. Retrieved 2014-01-22. 
  7. ^ "IEM Valid Time Extent Code (VTEC) App". Mesonet.agron.iastate.edu. Retrieved 2017-08-27. 
  8. ^ "Impact Based Warning Experimental Product". Crh.noaa.gov. Retrieved 2014-01-22. 
  9. ^ National Weather Service (2014). "Impact Based Warnings". National Oceanic and Atmospheric Administration. Retrieved March 12, 2014. 
  10. ^ "NWS Expirements" (PDF). NWS. Retrieved 15 April 2012. 
  11. ^ "'CATASTROPHIC': Experimental Tornado Warnings to be Explicit". AccuWeather. 2012-04-05. Retrieved 2014-03-12. 
  12. ^ http://forecast.weather.gov/product.php?site=NWS&issuedby=GSP&product=SVS&format=txt&version=1&glossary=0
  13. ^ National Weather Service (2014-01-05). "Iowa Environmental Mesonet NWS Product Archive". Retrieved 2014-01-06. 
  14. ^ "High Wind Warning - Hurricane Sandy". National Weather Service - Philadelphia/Mount Holly. Retrieved 29 October 2017. 
  15. ^ Payne, Ed; Shoichet, Catherine. "Running updates: Storms slam Houston, kill 31 in Texas, Oklahoma, Mexico". CNN. Retrieved 30 October 2017. 
  16. ^ "Tampa Bay/Ruskin - Severe Thunderstorm Warning". National Weather Service. Retrieved 30 October 2017. 

External links[edit]