RARE HURRICANE FORCE WINDS, HAIL AT PHOENIX, ARIZONA, DURING OBAMA'S SPEECH, AUG 28 2008



http://www.wrh.noaa.gov/psr/pns/2008/August/28thStorms.php


Major Severe Weather Event Across Phoenix
Updated: 12:00 PM 29 August 2008


Weather balloon data from the evening of the 28th. Note the large amount of instability with the weak cap. Also note the deep northeasterly flow in the mid levels.
During the day of the 28th, the sky was mostly clear across central Arizona. Early indications were that strong to severe thunderstorms were possible that evening, though by mid-afternoon little thunderstorm activity had developed. The weather balloon sounding data from Phoenix Thursday evening indicated that the atmosphere remained very unstable though a cap remained - analogous to a lid on a pot of boiling water (see graphic to right). In addition winds in the mid levels of the atmosphere were over 45 mph from the northeast, strongly unusual and indicative that thunderstorms that develop northeast of Phoenix will quickly move into the lower deserts and be capable of producing damaging winds.



Infrared satellite imagery. Click on the image for a larger version.

Shortly after 8 PM, thunderstorms began to develop east of Phoenix and moved into the potentially very unstable airmass. The thunderstorms themselves provided enough lift to release the stored energy - they took the lid off the pot. In the ensuing four hours severe thunderstorms spread across much of the south central Arizona, including much of the Phoenix Metropolitan Area. These were not your typical monsoon thunderstorms. NWS meteorologists noted the exceptionally strong structure of the thunderstorms, with the storms themselves extending up to 60,000 feet in the atmosphere. At this height the temperature of the tops of the thunderstorms was below -110 deg F (see graphic to right). For a satellite image loop, click here (0.8 MB).

As the evening unfolded several waves of thunderstorms, about four in total, developed generally east or northeast of Phoenix and moved to the west or southwest at speeds ranging from 20 to 40 mph. These types of thunderstorms are referred to as a line echo wave pattern (LEWP); line for a line of storms, echo for radar echoes, wave for the multiple waves of storms. LEWPs are common across the Mid-West United States, especially during the late evening and overnight hours. LEWPs are rather rare across central Arizona. What was even more rare was that the waves were traveling northeast to southwest; in the Mid-West the waves often travel in a general west to east direction. For a radar loop of the full event click here (large file - 17 MB).



80 to 100 mph winds measured by radar. Click on the image above for a full size version with accompanying text.
Early on it became evident that these thunderstorms would be capable of producing severe and damaging winds. This is what in fact happened as significant bow echoes developed within each wave. The highest measured wind speed reported to the NWS was 85 mph, which occurred near central Phoenix. Phoenix Sky Harbor International Airport reached 75 mph. Even the NWS office in Tempe was hit by the damaging winds. NWS meteorologists estimating winds to be at or above 80 MPH at the NWS office. Winds may have actually been higher than reported by any ground-based weather station as the National Weather Service radar recorded winds in excess of 100 MPH just 1,500 feet above the ground (see to right). For a loop of velocity radar data click here (large file - 14 MB).

The National Weather Service in Phoenix issued twenty Severe Thunderstorm Warnings and received thirty reports of severe weather during the event. The most significant wind measured was a wind gust of 85 MPH 4 miles SSE of downtown Phoenix by a trained weather spotter. The very strong winds resulted in widespread damage, with central Phoenix and north Tempe taking the brunt of the storm. Media coverage indicated that downed trees occurred over a large area with perhaps thousands of trees lost during the storm. Structural damage was also observed. The images below were taken by NWS Employees. Click on each thumbnail for a full version image.

To see rainfall total from across Maricopa County, visit the Flood Control District of Maricopa County. Reports from NWS automated and COOP observers will be available here.



The ASU football practice field was destroyed by the winds. Click for a full size version with accompanying text.



It is likely that thousands of trees like these fell during the storm. Click for a full size version with accompanying text.



It is likely that thousands of trees like these fell during the storm. Click for a full size version with accompanying text.



This covered parking was no match for the strong winds. Click for a full size version with accompanying text.



More structural damage. Click for a full size version with accompanying text.

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE PHOENIX AZ

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

0825 PM TSTM WND GST 2 S CHANDLER 33.27N 111.87W
08/28/2008 M77.00 MPH MARICOPA AZ AWOS

CHANDLER AIRPORT

0830 PM HEAVY RAIN 5 S CHANDLER 33.22N 111.88W
08/28/2008 M0.22 INCH MARICOPA AZ AMATEUR RADIO

0.22 INCH IN 5 MINS

0830 PM HEAVY RAIN 3 ENE CHANDLER 33.31N 111.82W
08/28/2008 M0.50 INCH MARICOPA AZ TRAINED SPOTTER

0.5 INCH RAIN IN 10 MINS

0840 PM HEAVY RAIN 5 W CHANDLER 33.29N 111.95W
08/28/2008 E0.50 INCH MARICOPA AZ TRAINED SPOTTER

0.5 INCH IN 30 MINS.

0850 PM HAIL 7 SW GUADALUPE 33.30N 112.06W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

3/4 INCH HAIL REPT LIBERTY LN AND DESERT FOOTHILLS PKWY

0850 PM HAIL 4 SW GUADALUPE 33.32N 112.00W
08/28/2008 E0.75 INCH MARICOPA AZ NWS EMPLOYEE

0906 PM HAIL NW MARICOPA 33.06N 112.05W
08/28/2008 E0.25 INCH PINAL AZ TRAINED SPOTTER

1/4 INCH HAIL COMPLETELY COVERING GROUND

0910 PM HEAVY RAIN 1 SW KINGS RANCH 33.37N 111.45W
08/28/2008 M0.50 INCH PINAL AZ TRAINED SPOTTER

HALF INCH RAIN IN 9 MINUTES

0912 PM HEAVY RAIN 4 E APACHE JUNCTION 33.40N 111.48W
08/28/2008 M0.00 INCH PINAL AZ TRAINED SPOTTER

0.27 INCH RAIN IN 7 MINUTES

0919 PM HEAVY RAIN 2 NW APACHE JUNCTION 33.42N 111.57W
08/28/2008 E0.00 INCH PINAL AZ TRAINED SPOTTER

1.2 INCH IN 25 MINS

0920 PM TSTM WND GST 3 NE MESA 33.45N 111.70W
08/28/2008 E75.00 MPH MARICOPA AZ TRAINED SPOTTER

RECKER AND BROWN

0920 PM HAIL 3 NE MESA 33.45N 111.70W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

BROWN AND RECKER IN EAST MESA

0921 PM HEAVY RAIN 5 WSW APACHE JUNCTION 33.39N 111.63W
08/28/2008 M0.00 INCH MARICOPA AZ TRAINED SPOTTER

0.5 INCH IN 15 MINS AT ELLSWORTH AND SOUTHERN

0930 PM TSTM WND DMG 5 SSW PARADISE VALLEY 33.47N 111.98W
08/28/2008 MARICOPA AZ TRAINED SPOTTER

TREES DOWN 48TH ST AND MCDOWELL WITH 40 MPH WINDS

0938 PM TSTM WND GST 6 NW TEMPE 33.44N 112.01W
08/28/2008 M75.00 MPH MARICOPA AZ ASOS

MEASURED ASOS AT PHX AIRPORT

0940 PM HAIL 4 SW GUADALUPE 33.32N 112.01W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

32ND AND RAY

0940 PM HAIL 4 SW GUADALUPE 33.32N 112.01W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

0940 PM HAIL 4 SW GUADALUPE 33.32N 112.01W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

32ND AND RAY IN AHWATUKEE

1000 PM HAIL 4 SW GUADALUPE 33.32N 112.01W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

1010 PM TSTM WND GST 4 SSE PHOENIX 33.48N 112.05W
08/28/2008 M85.00 MPH MARICOPA AZ AMATEUR RADIO

MEASURED WIND GUST 16TH ST AND THOMAS

1015 PM TSTM WND GST WSW ESTRELLA 33.00N 112.42W
08/28/2008 M69.00 MPH MARICOPA AZ TRAINED SPOTTER

ESTRELLA PKWY AND ELLIOT

1015 PM DUST STORM 4 SW WADDELL 33.54N 112.41W
08/28/2008 MARICOPA AZ TRAINED SPOTTER

1/4 MI VIS IN DUST STORM 4 MI WEST OF LUKE AFB

1043 PM TSTM WND DMG 5 N AVONDALE 33.49N 112.36W
08/28/2008 MARICOPA AZ TRAINED SPOTTER

2 FOOT DIAM TREE DOWN

1101 PM HAIL 6 WSW FOUNTAIN HILLS 33.58N 111.84W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

FRANK LLOYD WRIGHT AND SHEA

1105 PM HAIL 5 NNE PARADISE VALLEY 33.61N 111.93W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

SCOTTSDALE AND THUNDERBIRD

1105 PM HAIL 3 S SCOTTSDALE 33.64N 111.86W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

104ST AND BELL

1130 PM HAIL 5 NNE PARADISE VALLEY 33.61N 111.93W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

SCOTTSDALE AND THUNDERBIRD

1130 PM HAIL 2 W PHOENIX 33.54N 112.10W
08/28/2008 E0.75 INCH MARICOPA AZ TRAINED SPOTTER

18TH AND GLENDALE

1130 PM TSTM WND DMG 2 W PHOENIX 33.54N 112.10W
08/28/2008 MARICOPA AZ TRAINED SPOTTER

18 INCH DIAM TREE DOWN

1140 PM HAIL 2 WSW PARADISE VALLEY 33.53N 111.98W
08/28/2008 E1.00 INCH MARICOPA AZ TRAINED SPOTTER

TATUM AND LINCOLN




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