An Examination of a Dry-Season Severe Weather Event in the Borderland

Severe Thunderstorms of 3 April 2004: An Examination of a Dry-Season Severe Weather Event in the Borderland Michael P. Hardiman Joseph A. Rogash National Weather Service El Paso, Texas / Santa Teresa, New Mexico Overview On 3 April 2004 a rare Severe Thunderstorm event occurred in South-Central New Mexico and far West Texas… Pea to Golf ball-sized hail accumulated to a depth of 3-4 inches on US Highway 62/180 west of Cornudas, TX with reports of tennis ball-sized hail damaging vehicles in the area… 0.75 inch hail accumulated on roadways in the Silver City, NM area causing minor traffic accidents. Other accidents occurred on US 62/180 in Hudspeth County, TX… Overview On 3 April 2004 a rare Severe Thunderstorm event occurred in South-Central New Mexico and far West Texas… Golf ball-sized hail accumulated over 12 inches in depth in Chaparral, NM … damaging roofs, windows, and siding on homes on the north side of town… Photo by Greg Lundeen Overview On 3 April 2004 a rare Severe Thunderstorm event occurred in South-Central New Mexico and far West Texas… Key meteorological players included a mid/uppertropospheric closed low, mid-level cold pool, and associated moist southerly flow aloft… a process called “The Baja Tap.” Southeasterly low-level winds ahead of an approaching „backdoor‟ cold front resulted in deep low-level moisture. Resulting instability and shear profile sufficient for supercell thunderstorms… What’s in Store? • Overview of the EPZ CWA… “Where in the World is Cornudas, Texas?” • A Bit of Climatology… “Sure, it‟s El Paso, but still… why is this such a big deal?” • Synoptic Pattern… “Setting up for an (Omega) Block!” • Synoptic Analysis… “The ancient art of hand-analyzed charts…” • Mesoscale Analysis… Details, details, details… • Storm Evolution… Radar Imagery… • Conclusions... Followed by your Standing Ovation! (and questions too) EPZ CWA Overview Gila Wilderness Tularosa Basin Sacramento Mountains San Andres Mtns Organ Mtns Otero Mesa Guadalupe Mtns Franklin Mtns Hueco Mtns Delaware Mtns Sierra Blanca and Quitman Mtns Sierra Diablo Mtns Davis Mtns EPZ CWA Overview I-25 . I-10 Las Cruces . WSMR HQ Santa Teresa . . Chaparral . El Paso Cornudas . . Dell City US 62/180 I-10 Climatological Background Defining El Paso‟s Hydrologic Seasons… Percent of Annual Rainfall Pseudo-Monsoon: 51% Transition Months: 16% Dry Season: 33% (over 7 months) April: 3% (Driest Month on average) Climatological Background Defying El Paso‟s Hydrologic Seasons… Percent of Annual Rainfall Pseudo-Monsoon: 51% Transition Months: 16% Dry Season: 33% (over 7 months) April: 3% (Driest Month on average) April 2004: 1.06 in. (408% of Normal) 0.53 in. from 2-5th April Climatological Background Hail Climatology… Total Number of Severe Hail Reports Severe Criteria Hail: ≥ 0.75 inch diameter (From Reynolds 1999) Only 6 Reports of April Severe-Criteria Hail in EPZ County Warning Area since 1955!!! Climatological Background “Typical” active April Pattern: • Strong, Dry Southwesterly flow aloft… • Clear skies, lots of mixing, strong surface gradient from lee side low… • Perfect recipe for strong winds, blowing dust. Climatological Background “Typical” active April Pattern: • Strong, Dry Southwesterly flow aloft… • Clear skies, lots of mixing, strong surface gradient from lee side low… • Perfect recipe for strong winds, blowing dust. Synoptic Pattern Setting up for a Block… 23 March 2004 Daily Average 500 mb Geopotential Heights • Blocking high over Atlantic causes eastern U.S. trough to lift poleward… •Pattern over CONUS starts becoming zonal… Synoptic Pattern Setting up for a Block… 24 March 2004 Daily Average 500 mb Geopotential Heights • Blocking high over Atlantic causes eastern U.S. trough to lift poleward… •Pattern over CONUS starts becoming zonal… Synoptic Pattern Setting up for a Block… 25 March 2004 Daily Average 500 mb Geopotential Heights • Zonal flow (high index pattern) is achieved… • Shortwave over Newfoundland encounters persistent Atlantic blocking high… Synoptic Pattern Setting up for a Block… 26 March 2004 Daily Average 500 mb Geopotential Heights • Zonal flow (high index pattern) begins to break down with Pacific Northwest trough… • Newfoundland shortwave begins to dig southward… Synoptic Pattern Setting up for a Block… 27 March 2004 Daily Average 500 mb Geopotential Heights • Pattern starts becoming more “wavelike” in nature… • Newfoundland shortwave digs further, begins to break down Atlantic blocking high… Synoptic Pattern Setting up for a Block… 28 March 2004 Daily Average 500 mb Geopotential Heights • Wavy (“Low Index”) pattern is achieved… Synoptic Pattern Setting up for a Block… 29 March 2004 Daily Average 500 mb Geopotential Heights • Wavy (“Low Index”) pattern continues… • Atlantic blocking high reduced to a weak ridge… • Old Newfoundland trough has dug down to the Bahamas, begins to get cut off… Synoptic Pattern Setting up for a Block… 30 March 2004 Daily Average 500 mb Geopotential Heights • Wavy (“Low Index”) pattern continues… • “High over Low” block forms off the East Coast as old Newfie trough cuts off… • Active, “wavy” pattern gets backed-up, eastern US ridge is forced over the new cut-off low… Synoptic Pattern Setting up for a Block… 31 March 2004 Daily Average 500 mb Geopotential Heights • Omega Block starts taking shape… • East coast ridge shears off, pattern remains blocked up. • Central US high is forced northward, starts cutting-off Midwest trough… • West coast trough digs south due to backed up pattern… Synoptic Pattern Setting up for a Block… 01 April 2004 Daily Average 500 mb Geopotential Heights • Omega Block starts to take shape… • Midwest trough cuts off… • Central US ridge strengthens… • West coast trough cuts off… • (Let the fun begin!) Synoptic Pattern Setting up for a Block… 02 April 2004 Daily Average 500 mb Geopotential Heights • Omega Block in place! • Cut-off sitting over the MidAtlantic states… • Ridge over the Plains… • Cut-off low sets up shop over Southern California… Synoptic Pattern Setting up for a Block… 03 April 2004 Daily Average 500 mb Geopotential Heights • Omega Block in place! • Cut-off still sitting over the Mid-Atlantic states… • Ridge over the Plains… • Cut-off low crawls into Arizona. • The stage is set… Synoptic Analysis 250mb Analysis 0000 UTC 04 April 2004 •Polar jet stream in a split flow •Subtropical Jet far south •Diffluence axis between southern branch of Polar Jet and 50+ knot jet maxima induced by cut-off low Synoptic Analysis 250mb Analysis • Polar jet stream in a split flow • Subtropical Jet far south • Diffluence axis between southern branch of Polar Jet and 50+ knot jet maxima Induced by cut-off low • Jet streak also evident from cirrus shield on lee-side of mountain peaks in Mexico • 18z GFS Analysis indicates 80 knot jet streak • (RUC, ETA also in general agreement…) Synoptic Analysis 500mb Analysis 0000 UTC 04 April 2004 • Strong “anomalous” cut-off low over Arizona… (How anomalous was it ???) Synoptic Analysis 500mb Analysis •500 mb Geopotential Height anomaly of -160 meters •500 mb Temperature anomaly of -7° Celsius Source: NCEP Operational Dataset (1980-2004) from the CDC website. Synoptic Analysis 500mb Analysis 0000 UTC 04 April 2004 • Strong “anomalous” cut-off low over Arizona… • Mid-level jet maxima of 50-60 knots over New Mexico… Synoptic Analysis 500mb Analysis • Strong “anomalous” cut-off low over Arizona… • Mid-level jet maxima of 50-60 knots over New Mexico… • Confirmed on WSMR profiler Synoptic Analysis 500mb Analysis 0000 UTC 04 April 2004 • Strong “anomalous” cut-off low over Arizona… • Mid-level jet maxima of 50-60 knots over New Mexico… • Confirmed on WSMR profiler • Mid-level Moisture advection (low dew point depressions) “The Baja Tap!” • Cold Pool aloft (-23° Celsius at Tucson…) Synoptic Analysis Water Vapor Imagery Regional Scale Synoptic Analysis 700mb Analysis 0000 UTC 04 April 2004 • Low-level moisture advection over the Southwestern USA. • SE winds at EPZ (deep-layer directional shear) Synoptic Analysis Surface Analysis 1800 UTC 03 April 2004 • No strong surface reflection of mid/upper-level cut-off… • Weak low analyzed over western Arizona • Weak troughing over southwest NM and Chihuahua. • Main feature: Back-door cold front slowly sliding southwest, getting caught up against the higher terrain… • Southeasterly flow ahead of front beginning to leach into far west Texas and S/C NM. • Low-level moisture also is encountering higher terrain. Synoptic / Mesoscale Visible Satellite Mesoscale Analysis Surface Analysis 1800 UTC 03 April 2004 • Cold Front banked up against Mountains. • 1007 mb low over NE Durango, Mexico. • Trough extending North through Southwest New Mexico. • Apparent Wind Shift line / Dewpoint boundary in vicinity of Cu Line. • Cu line appears to be west of higher terrain Mesoscale Analysis Note thin line Mesoscale Analysis Eta Cross-Sections 12z 04/03/2004 run +00hr Valid 12z 04/03/2004 • Model cross sections useful to back up our reasoning… •Show X-section line on a nice topo/relief map • From ArcView or Fermi maps • Also helpful due to lack of surface obs east of ELP Mesoscale Analysis Eta Cross-Sections 12z 04/03/2004 run +00hr Valid 12z 04/03/2004 • Deeper low-level moisture evident east of the higher terrain (Delaware Mtns) • Deep moisture also seems to be making it over the Delaware Mtns Lordsburg ELP Hueco Mtns Delaware Mtns (S of GDP) Big Burro Mtns Florida Mtns Potrillo Mtns Franklin Mtns Mesoscale Analysis Eta Cross-Sections 12z 04/03/2004 run +06hr Valid 18z 04/03/2004 • Deeper low-level moisture evident east of the higher terrain (Delaware Mtns) • Deep moisture also seems to be making it over the Delaware Mtns Lordsburg ELP Hueco Mtns Delaware Mtns (S of GDP) Big Burro Mtns Florida Mtns Potrillo Mtns Franklin Mtns Mesoscale Analysis Eta Cross-Sections 12z 04/03/2004 run +12hr Valid 00z 04/04/2004 • ~1 hour after Cornudas storm • Note dewpoint gradient and low-level convergence East of Hueco Mountains… • Dewpoints drop off sharply to the West (near ELP) Lordsburg ELP Hueco Mtns Delaware Mtns (S of GDP) Big Burro Mtns Florida Mtns Potrillo Mtns Franklin Mtns Mesoscale Analysis RUC Surface Analyses 1800 UTC 04/03/2004 Mesoscale Analysis RUC Surface Analyses 1900 UTC 04/03/2004 Mesoscale Analysis RUC Surface Analyses 2000 UTC 04/03/2004 Mesoscale Analysis RUC Surface Analyses 2100 UTC 04/03/2004 Mesoscale Analysis RUC Surface Analyses 2200 UTC 04/03/2004 Analyses clearly indicate our dewpoint/wind shift boundary and also show sfc dewpoints ~50° F in eastern El Paso County… Sounding Analysis 0000 UTC 04 April 2004 ~UNMODIFIED~ Notice the Surface Dewpoint at EPZ is only 2°C (36°F) … Not representative of conditions further East! Similarly, Surface Temperature is also rather low at 21°C (70°F) Sounding Analysis Regional Surface Observations Temperature/Dewpoint (°F) Time (UTC) 1800 1900 2000 2100 2200 2300 0000 0100 EPZ/5T6 Santa Teresa, NM NWS WFO 16 NW ELP Sounding Modification Reasoning Surface Dewpoints around El Paso dropped into the mid 30s throughout the afternoon leading up to the RAOB release at 0000 UTC. ELP El Paso International Airport 11 NE ELP (DAPM Bruce Bradley‟s Home) 63/46 64/46 68/37 70/36 MM/MM 72/30 70/36 70/30 63/46 68/39 70/37 70/37 72/39 72/41 72/39 64/46* 72/48 74/44 75/42 75/42 76/43 76/44 72/46 63/46* RUC 2hr Forecast valid at 2300 UTC (time of RAOB release) indicates dewpoints in low 50s in eastern El Paso County, east of the boundary. Note the temperature of 76°F on the East Side of El Paso at 2300 UTC Dell City COOP Observer recorded a high temperature of 80°F for the date, likely set around 2300 UTC. Sounding Analysis Regional Surface Observations Temperature/Dewpoint (°F) Time (UTC) 1800 1900 2000 2100 2200 2300 0000 0100 EPZ/5T6 Santa Teresa, NM NWS WFO 16 NW ELP Sounding Modification Reasoning Surface Dewpoints around El Paso dropped into the mid 30s throughout the afternoon leading up to the RAOB release at 0000 UTC. ELP El Paso International Airport 11 NE ELP (DAPM Bruce Bradley‟s Home) 63/46 64/46 68/37 70/36 MM/MM 72/30 70/36 70/30 63/46 68/39 70/37 70/37 72/39 72/41 72/39 64/46* 72/48 74/44 75/42 75/42 76/43 76/44 72/46 63/46* RUC 2hr Forecast valid at 2300 UTC (time of RAOB release) indicates dewpoints in low 50s in eastern El Paso County, east of the boundary. Note the temperature of 76°F on the East Side of El Paso at 2300 UTC Dell City COOP Observer recorded a high temperature of 80°F for the date, likely set around 2300 UTC. Modified Sounding Surface Conditions: T = 79° F Td = 51° F Sounding Analysis 0000 UTC 04 April 2004 ~MODIFIED~ Sounding Analysis 0000 UTC 04 April 2004 ~UNMODIFIED~ The Cornudas Storm The Chaparral Storm Photo by Greg Lundeen 0007 UTC 04/04/2004 0013 UTC 04/04/2004 0018 UTC 04/04/2004 0024 UTC 04/04/2004 0030 UTC 04/04/2004 Az= 51º Region of heaviest hail and damage… Max 72 dBz Chaparral Damage Photos John Fausett and Bill Alexander Last Slide Any Questions???