Particularly dangerous situation

From Wikipedia, the free encyclopedia

In weather forecasting in the United States, "particularly dangerous situation" (PDS) is enhanced wording used by the National Weather Service to convey special urgency in some watch or warning messages when there is a significant risk of extreme weather, most commonly from types of weather events that are usually less severe by comparison, such as a severe thunderstorm outbreak or flash flooding. It is used in the format "This is a particularly dangerous situation..." at the discretion of the issuing forecaster. A watch or warning bearing the phrase is referred to as a PDS watch or PDS warning as shorthand jargon.

It was first used by the Storm Prediction Center (SPC), a national guidance center of the National Weather Service, for tornado watches and eventually expanded to use for other severe weather watches and warnings by the agency's regional forecast offices. It is most commonly used for major tornado outbreaks or long-lived, extreme derecho events, and has been used for non-convective weather hazards such as exceptional flash flooding, or a wildfire.[1][2]

PDS watches and warnings alike 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.[3] 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 short history of the origin of the option of issuing a tornado watch with the enhanced PDS wording occurred during the winter of 1981–82 when the Severe Local Storms (SELS) unit transitioned to a more flexible method of issuing weather products. Ed Ferguson, Deputy Director of the National Severe Storms Forecast Center (NSSFC), suggested to Lead Forecaster Jack Hales that the guidance center could provide an opportunity to give more resolution to the tornado watch product. Hales suggested the PDS option to identify areas where, a few times each year, conditions are most likely to aid in the development of large and intense tornadoes. 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.[4]

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.

On December 19, 2017, and August 3, 2018, the National Weather Service Weather Forecast Office in Reno, Nevada, issued PDS red flag warnings to highlight the threat for potentially life-threatening fire danger due to strong gusty winds and low humidity.

Issuance[edit]

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.

Below is the first PDS flash flood watch, which was issued by the National Weather Service Forecast Office in Memphis, Tennessee, on April 24, 2011, as mentioned above.[5]

PDS flash 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
 
 * 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

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 and Corpus Christi, Texas.

This warning was issued in the morning of May 30, 2018, by the National Weather Service Forecast Office in GreenvilleSpartanburg, South Carolina, while Subtropical Storm Alberto was affecting the area. It was also issued on September 1, 2021, by the National Weather Service Forecast Office in New York, New York while the remnants of Hurricane Ida affected the region. It also contains the flash flood emergency phrase, which further underscores the risk of life-threatening flash flooding.[6][7]

PDS flash flood warning
 NCC111-301630-
 /O.EXT.KGSP.FF.W.0034.000000T0000Z-180530T1630Z/
 00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO
 
 BULLETIN - EAS ACTIVATION REQUESTED
 Flash Flood Warning
 National Weather Service Greenville-Spartanburg SC
 626 AM EDT WED MAY 30 2018
 
 ...FLASH FLOOD EMERGENCY CONTINUES FOR AREAS DOWNSTREAM OF LAKE TAHOMA
 DUE TO POTENTIAL IMMINENT FAILURE OF TAHOMA DAM...MANDATORY
 EVACUATIONS UNDERWAY...
 
 The National Weather Service in Greenville-Spartanburg has extended
 the 
 
 * Flash Flood Warning for...
 Central McDowell County in western North Carolina...
 
 * Until 1230 PM EDT Wednesday.
 * At 611 AM EDT, Emergency Management is reporting that the risk of
 imminent failure remains at Lake Tahoma Dam and mandatory
 evacuations remain in effect.  This emergency evacuation was
 issued at the recommendation of dam engineers who remain on scene
 to monitor the dam.  Lake Tahoma Dam is currently in a Level 1 or
 Imminent Failure Condition.  This condition will continue until
 the engineers have the opportunity to thoroughly inspect the dam
 during daylight hours.  THIS IS AN EXTREMELY DANGEROUS
 SITUATION! MANDATORY EVACUATIONS are underway for ALL residents
 and businesses downstream of Lake Tahoma along Buck Creek and
 along the Catawba River from Buck Creek and Lake Tahoma Rd (NC 80)
 to the mouth of Lake James.  To save your life, please heed all
 county evacuation notices and take action to leave the vicinity
 immediately!
 
 Repeating, this is a FLASH FLOOD EMERGENCY for McDowell County for
 areas downstream of Lake Tahoma and Lake Tahoma Dam to the mouth
 of Lake James along the Catawba River. This is a PARTICULARLY
  DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!
 
 * Repeating, mandatory evacuations remain underway from Lake Tahoma
 Dam at Lake Shore Dr down Lake Tahoma Rd (NC 80) to the confluence
 of the Catawba River near US 70, Resistoflex Rd, and Riverside
 Park. Residences and businesses along US 70 from Lake Tahoma Rd to
 US 221 Business near Garden Creek, as well as areas along Hankins
 Rd. to the mouth of Lake James are included in the mandatory
 evacuation.  LEAVE NOW!
 
 * Evacuees are being asked to seek shelter at the Glenwood Baptist
 Church, the Old Fort Baptist Church, or the YMCA in Marion near
 McDowell Hospital.
 
 * Some locations that are experiencing flooding include...
 Pleasant Gardens, northwest Marion, and Lake James.
 
 * The excessive rainfall over the warned area has caused numerous
 mud slides and additional mud slides are possible near steep
 terrain. The mud slide can consist of rock, mud, vegetation and
 other loose materials and are very powerful.
 
 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.
 
 Most flood deaths occur in vehicles. Do not attempt to cross
 water-covered roadways, bridges, or low-level crossings. Only a few
 inches of rapidly flowing water can carry away your vehicle. It is
 not worth the risk. Please TURN AROUND, DON`T DROWN.
 
 The floodwave along Buck Creek above and below Lake Tahoma will
 increase the risk of landslides, especially in areas where slides
 have occurred in the past. Be especially alert if you are near a
 stream, especially at the base of a mountain or in a cove. Watch
 for loose-moving soil and rocks or a sudden increase in streamflow.
 Leave the area quickly if this is observed. When driving along
 roads where the terrain is steep or rocky, watch and listen for
 falling rocks, mud, trees and other debris.
 
 &&
 
 LAT...LON 3574 8207 3572 8205 3574 8202 3574 8198
 3570 8196 3570 8200 3567 8206 3573 8211
 
 $$
 
 JMP

PDS high wind warning[edit]

PDS high wind warnings are issued by the National Weather Service when non-convective winds are expected to be especially damaging or dangerous to people and property, beyond what would be expected of a typical high wind warning.

The warning below was issued by the National Weather Service in Salt Lake City, Utah, on September 8, 2020, for an extreme downslope wind event in Salt Lake City and the northern Wasatch Front.[8]

PDS high wind warning
URGENT - WEATHER MESSAGE
National Weather Service Salt Lake City UT
911 AM MDT Tue Sep 8 2020

UTZ002-003-082315-
/O.CON.KSLC.HW.W.0006.000000T0000Z-200909T1500Z/
Northern Wasatch Front-Salt Lake and Tooele Valleys-
Including the cities of Ogden, Bountiful, and Salt Lake City
911 AM MDT Tue Sep 8 2020

...HIGH WIND WARNING REMAINS IN EFFECT UNTIL 9 AM MDT WEDNESDAY...

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

* WHAT...East winds 30 to 45 mph with gusts in excess of 70 mph
  are expected. Wind gusts as high as 98 mph near Farmington,
  Centerville and the mouth of Weber Canyon have been reported
  this morning. This is a particularly dangerous situation.

* WHERE...Salt Lake and Tooele Valleys and Northern Wasatch
  Front.

* WHEN...Until 9 AM MDT Wednesday.

* IMPACTS...High winds may move loose debris, damage property
  and cause power outages. Travel will be difficult especially
  for high profile vehicles. The most impacted travel routes are
  expected to be along the I-15 corridor between Salt Lake City
  and Layton, the Legacy Parkway, the US 89 corridor in Davis
  and Weber Counties, and Foothill Drive.

* ADDITIONAL DETAILS...Stay inside! Flying debris and numerous
  falling trees may be deadly.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

People are urged to secure loose objects that could be blown
around or damaged by the wind.

&&

$$

PDS red flag warning[edit]

PDS red flag warnings are issued by the National Weather Service to inform the public that there is an unusually high threat of wildland fire combustion, and rapid spread of wildfires, due to very dry fuels, very low humidity levels, and strong winds.

The PDS red flag warning below was issued by the National Weather Service in Reno, Nevada, on December 19, 2017.[9]

On August 3, 2018, the National Weather Service in Reno, Nevada, issued another PDS red flag warning to communicate the threat of life-threatening fire danger due to strong gusty winds and low humidity.

On April 12, 2022, the National Weather Service in Norman, Oklahoma, issued a PDS red flag warning because of an extreme fire weather behavior (overlap of extremely dry fuels, humidity as low as 8 percent and wind gusting to 60 mph).[10]

PDS red flag warning
 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.
 

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).[3]

This PDS severe thunderstorm watch shown below was issued by the Storm Prediction Center in Norman, Oklahoma, on May 12, 2022, for a derecho in portions of Iowa, Minnesota, Nebraska, and South Dakota.[11]

PDS severe thunderstorm watch
  SEL8
  URGENT - IMMEDIATE BROADCAST REQUESTED
  Severe Thunderstorm Watch Number 208
  NWS Storm Prediction Center Norman OK
  325 PM CDT Thu May 12, 2022
  The NWS Storm Prediction Center has issued a
  * Severe Thunderstorm Watch for portions of 
    Northwest Iowa
    Southwest Minnesota
    Northeast Nebraska
    Southeast South Dakota
  * Effective this Thursday afternoon and evening from 325 PM until
    1000 PM CDT.
  ...THIS IS A PARTICULARLY DANGEROUS SITUATION...
  * Primary threats include...
    Widespread damaging winds and scattered significant gusts to 105
      mph expected
    Scattered large hail likely with isolated very large hail events
      to 2 inches in diameter possible
    A couple tornadoes possible
  SUMMARY...A prolific wind-damage event is expected unfold from
  northeast Nebraska into southeast South Dakota and northwest
  Iowa/southwest Minnesota. Pockets of significant wind damage are
  highly likely, along with the potential for large hail and possible
  a line-embedded tornado or two.
  The severe thunderstorm watch area is approximately along and 60
  statute miles north and south of a line from 60 miles west of
  Mitchell SD to 5 miles east northeast of Spencer IA. For a complete
  depiction of the watch see the associated watch outline update
  (WOUS64 KWNS WOU8).
  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 205...WW 206...WW 207...
  AVIATION...A few severe thunderstorms with hail surface and aloft to
  2 inches. Extreme turbulence and surface wind gusts to 90 knots. A
  few cumulonimbi with maximum tops to 550. Mean storm motion vector
  22045.
  ...Guyer

PDS special marine warning[edit]

PDS Special marine warnings are issued by the National Weather Service to inform mariners of weather conditions that present a considerable threat to life and property.

On April 19, 2018, the Baltimore/Washington, D.C. forecast office upgraded a special marine warning to PDS status as a gust front approached Chesapeake Bay.[12]

PDS special marine warning
National Weather Service Baltimore MD/Washington DC
 1138 AM EDT THU APR 19 2018
 
 ANZ537-191700- 
 /O.CON.KLWX.MA.W.0020.000000T0000Z-180419T1700Z/
 1138 AM EDT THU APR 19 2018
 
 ...A SPECIAL MARINE WARNING REMAINS IN EFFECT UNTIL 100 PM EDT...
 
 For the following areas...
 Tidal Potomac from Cobb Island MD to Smith Point VA...
 
 At 1137 AM EDT, a gust front was located near Quantico Marine Base,
 moving southeast at 25 knots. Numerous wind gusts of 35 to 45 knots
 have been observed with this line.
 
 HAZARD...Wind gusts 34 knots or greater.
 
 SOURCE...Radar indicated.
 
 IMPACT...Boaters in small craft could be thrown overboard by
 suddenly higher winds and waves capsizing their vessel.
 
 Locations impacted include...
 Yeocomico River...
 Breton Bay...
 Point Lookout...
 Coltons Point...
 Saint Clements Bay...
 Coles Point...
 Mouth Of The Potomac River...
 Saint George Island...
 White Point Beach...
 Tall Timbers...
 and Piney Point.
 
 PRECAUTIONARY/PREPAREDNESS ACTIONS...
 
 This is a particularly dangerous situation. Sudden onset of gale
 force winds can cause even experienced mariners to capsize.
 Capsizing in cold water is especially dangerous and can quickly
 result in hypothermia. If you haven't already done so, move to safe
 harbor now!
 
 &&
 
 LAT...LON 3797 7641 3801 7647 3802 7651 3807 7654
 3811 7660 3815 7661 3817 7676 3817 7685
 3826 7686 3825 7684 3823 7660 3821 7657
 3814 7652 3806 7633 3801 7629 3791 7627
 TIME...MOT...LOC 1537Z 310DEG 27KT 3871 7777 3813 7848
 
 
 HAIL...0.00in
 WIND...>34kts
 
 $$
 
 DHOF

PDS special weather statement[edit]

PDS special weather statements are usually issued by the NWS for hazards that do not have a specific code of their own, and pose an exceptionally high risk of damage and loss of life.

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.[citation needed] The same office issued multiple PDS Special Weather Statements for hurricane-force winds forecast to hit the Buffalo area on February 24, 2019.[13][14][15]

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 tornado watch[edit]

PDS tornado watches are issued when there is a significantly higher than normal risk of multiple EF2 or stronger 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. Under current criteria, such would be issued when the probability for significant tornadoes is 80% or greater. PDS Tornado Watches are often issued on high risk days for severe weather, though have been issued on high-end moderate risk days.

The PDS tornado watch shown below was issued on March 31, 2023.[16]

PDS tornado watch

SEL7

  URGENT - IMMEDIATE BROADCAST REQUESTED
  Tornado Watch Number 97
  NWS Storm Prediction Center Norman OK
  555 PM CDT Fri Mar 31 2023
  The NWS Storm Prediction Center has issued a
  * Tornado Watch for portions of 
    Northwestern Alabama
    Northern Mississippi
    Western and Middle Tennessee
  * Effective this Friday afternoon and Saturday morning from 555
    PM until 100 AM CDT.
  ...THIS IS A PARTICULARLY DANGEROUS SITUATION...
  * Primary threats include...
    Several tornadoes and a few intense tornadoes likely
    Scattered damaging winds and isolated significant gusts to 80
      mph likely
    Scattered large hail and isolated very large hail events to 2.5
      inches in diameter possible
  SUMMARY...The threat for both discrete, tornadic supercells and an
  eventual severe squall line will spread across the watch area
  through the evening.  A favorably unstable, strong-shear environment
  will support the threat for significant (EF2+) tornadoes.  Severe
  thunderstorm gusts and large, locally damaging hail also are
  expected.
  The tornado watch area is approximately along and 85 statute miles
  east and west of a line from 40 miles south of Oxford MS to 25 miles
  east northeast of Clarksville TN. For a complete depiction of the
  watch see the associated watch outline update (WOUS64 KWNS WOU7).
  PRECAUTIONARY/PREPAREDNESS ACTIONS...
  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 93...WW 94...WW 95...WW
  96...
  AVIATION...Tornadoes and a few severe thunderstorms with hail
  surface and aloft to 2.5 inches. Extreme turbulence and surface wind
  gusts to 70 knots. A few cumulonimbi with maximum tops to 550. Mean
  storm motion vector 25045.
...Edwards

[17]

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.[18] The criteria for a PDS warning are when a tornado on the ground has been spotted or confirmed, or a significant tornado is expected based on 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[19]); 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.[20][21]

Below is an example of a PDS Tornado Warning from the Darien EF3 tornado on June 20 2021.

PDS tornado warning

865
WWUS54 KJAN 200016
SVSJAN

Severe Weather Statement
National Weather Service Chicago/Romeoville 
1115pm 

MSC073-091-200100-
/O.CON.KJAN.TO.W.0043.000000T0000Z-200420T0100Z/
Dupage County
716 PM CDT Sun Apr 19 2020

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 800 PM CDT FOR MARION
AND LAMAR COUNTIES...

At 1112 PM CDT, a confirmed large and extremely dangerous tornado was
located over Darien, or over Far East Woodridge, moving east at 45 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...
  
  Burr ridge, Western Springs, and Indian Head Park around 1120 PM CDT.
  Palos Hills, Justice, Summit, Bridgeview, Hickory Hills, Contryside, Willow Springs, and Hodgkins around 1125 PM

Oak Lawn, Midway Airport, Burbank, Alsip, Chicago Ridge, Palos Heights, Crestwood and Worth around 1130 PM CDT.
Other locations in the path of this tornadic thunderstorm include Chicago Lawn, And Oak Forest.

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.

&&

OEMC zones… 8 & 10

LAT...LON 3101 8950 3101 8955 3100 8955 3100 8983
      3107 8984 3108 8992 3113 8994 3113 9001
      3117 9001 3118 9003 3128 9004 3134 8935
      3101 8935 3101 8942 3098 8943 3098 8947
TIME...MOT...LOC 0015Z 266DEG 37KT 3110 8988

TORNADO...OBSERVED
TORNADO DAMAGE THREAT...Considerable 
HAIL...0.75

$$

DC 
[22]

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.[23]

PDS wind chill warning
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

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, or extreme heat. 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!"[24] 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..."[25] 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."[26]

References[edit]

  1. ^ NOAA (2004-04-18). "Storm Prediction Center Frequently Asked Questions (FAQ)". Retrieved 2008-05-23.
  2. ^ "National Weather Service Issues Area Red Flag Warning". Retrieved 2018-08-04.
  3. ^ a b 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.
  4. ^ Lewis, John (2007-11-03). "A Forecaster's Story: Robert H. Johns". Electronic Journal of Severe Storms Meteorology. 2 (7). doi:10.55599/ejssm.v2i7.12.
  5. ^ "IEM Valid Time Extent Code (VTEC) App". Mesonet.agron.iastate.edu. Retrieved 2014-01-22.
  6. ^ "Flash Flood Warning". National Weather Service. 2018-05-30. Retrieved 2018-05-30.
  7. ^ "Flash Flood Warning". National Weather Service. 2021-09-01. Retrieved 2021-09-01.
  8. ^ National Weather Service (2020-09-08). "Iowa Environmental Mesonet NWS Product Archive". Retrieved 2020-09-08.
  9. ^ National Weather Service (2017-12-19). "Iowa Environmental Mesonet NWS Product Archive". Retrieved 2018-04-18.
  10. ^ "IEM :: Valid Time Event Code (VTEC) App".
  11. ^ NOAA (2022-05-12). "Storm Prediction Center: Particularly Dangerous Situation (PDS) Severe Thunderstorm Watch 208".
  12. ^ Herzmann, Daryl. "IEM :: Valid Time Event Code (VTEC) App". mesonet.agron.iastate.edu. Retrieved 2018-04-19.
  13. ^ herzmann, daryl. "IEM :: SPS from NWS BUF". mesonet.agron.iastate.edu. Retrieved 2023-01-18.
  14. ^ herzmann, daryl. "IEM :: SPS from NWS BUF". mesonet.agron.iastate.edu. Retrieved 2023-01-18.
  15. ^ herzmann, daryl. "IEM :: SPS from NWS BUF". mesonet.agron.iastate.edu. Retrieved 2023-01-18.
  16. ^ "Storm Prediction Center PDS Tornado Watch 97". Storm Prediction Center. Storm Prediction Center. Retrieved 31 March 2023.
  17. ^ Brugge, R. (December 1994). "The Alabama tornado outbreak of 27 March 1994 - an example of tornado formation". Weather. 49 (12): 407–411. Bibcode:1994Wthr...49..407B. doi:10.1002/j.1477-8696.1994.tb05961.x. ISSN 0043-1656.
  18. ^ "Impact Based Warning Experimental Product". Crh.noaa.gov. Retrieved 2014-01-22.
  19. ^ National Weather Service (2014). "Impact Based Warnings". National Oceanic and Atmospheric Administration. Retrieved March 12, 2014.
  20. ^ "NWS Expirements" (PDF). NWS. Archived from the original (PDF) on 13 April 2012. Retrieved 15 April 2012.
  21. ^ "'CATASTROPHIC': Experimental Tornado Warnings to be Explicit". AccuWeather. 2012-04-05. Archived from the original on 2014-03-13. Retrieved 2014-03-12.
  22. ^ "Tornado Warning". Iowa State University Iowa Environmental Mesonet. National Weather Service Forecast Office in Jackson, Mississippi. Retrieved 30 September 2020.
  23. ^ National Weather Service (2014-01-05). "Iowa Environmental Mesonet NWS Product Archive". Retrieved 2014-01-06.
  24. ^ "High Wind Warning – Hurricane Sandy". National Weather Service – Philadelphia/Mount Holly. Retrieved 29 October 2017.
  25. ^ Payne, Ed; Shoichet, Catherine (26 May 2015). "Running updates: Storms slam Houston, kill 31 in Texas, Oklahoma, Mexico". CNN. Retrieved 30 October 2017.
  26. ^ "Tampa Bay/Ruskin – Severe Thunderstorm Warning". National Weather Service. Retrieved 30 October 2017.

Public Domain This article incorporates public domain material from websites or documents of the National Oceanic and Atmospheric Administration.

External links[edit]