source: NWS

source: NWS

source: NWS

source: NWS

 RAINFALL STORM TOTAL SUMMARY...PRELIMINARY
 NATIONAL WEATHER SERVICE SAN DIEGO CA
 530 AM PDT THU JUN 4 2009

 BEGINNING:  1200 AM PDT WED JUN 3 2009
    ENDING:  1100 PM PDT WED JUN 3 2009

 ...RARE EARLY JUNE THUNDERSTORMS...

 UNSTABLE AIR ASSOCIATED WITH AN UPPER LEVEL LOW OFF THE COAST CAUSED
 ISOLATED THUNDERSTORMS AND BRIEF SHOWERS OVER THE AREA ON WEDNESDAY.
 THE CELLS WERE VERY HIGH BASED AND MOVED VERY QUICKLY FROM SOUTHWEST
 TO NORTHEAST AT ABOUT 40 MPH. PRECIPITATION WAS ISOLATED AND MOSTLY
 LESS THAN ONE TENTH OF AN INCH...BUT A COUPLE OF PLACES GOT OVER ONE
 QUARTER OF AN INCH. HUNDREDS OF LIGHTNING STRIKES...SMALL HAIL...AND
 GUSTY WINDS WITH THE MOUNTAIN AND DESERT THUNDERSTORMS HAD THE
 GREATER IMPACT. A DOWNBURST NEAR LUCERNE VALLEY WAS MEASURED AT 52
 MPH. DOZENS OF FIRES WERE SET...ESPECIALLY IN SAN BERNARDINO
 COUNTY...AND A LEAST ONE FATALITY DUE TO LIGHTNING WAS REPORTED IN
 SAN BERNARDINO COUNTY.

Lightning Strikes 6/3/09

Click image for full size Source: National Weather Service (San Diego)

Of the 31 days in May...

27 days were above average for the high
only 4 days were at or below the average high

Take the entire month and the average high was 5.6 degrees above average

For the morning lows…
only 3 nights were at or below the average low

Take the entire month and the average low was 6.5 degrees above average

data is from the NWS for Palm Springs

New Hail Criteria

The National Weather Service (NWS) Central Region has conducted a demonstration in the state of Kansas and adjoining County Warning Areas over the past four years, utilizing a hail size criterion for issuance of Severe Thunderstorm Warnings of 1” in diameter, rather than the historical 3/4” threshold. This experiment was based on feedback from local partners (emergency managers, media, public, etc.), as well as scientific research conducted by Texas Tech University which demonstrated that significant property damage does not occur until hailstone sizes reach 1” in diameter.

Customer responses have indicated high satisfaction with adoption of the 1″ hail criterion. Our media partners said warnings are more meaningful because the public knows there is a genuine risk of damage when a Severe Thunderstorm Warning is issued and fewer complaints are fielded from viewers/listeners of excessive interruptions into programming. Emergency managers agree that warnings carry more weight and credibility.

Click here to see a video explaining this change.

Based on the favorable response from partners and customers, the NWS Western Region (WR) will implement a similar demo for all 8 NWS WR states, on June 1 to catch the main severe weather season for both the northern tier of NWS WR and the southwest monsoon season. This implementation will also eliminate potential CWA/state border issues between CR and WR offices. Information for organized strong, but less than severe, thunderstorms will be provided via a Significant Weather Advisory. For pulse-type storms of moderate strength that are not expected to last long, NWS offices may issue a Short Term Forecast or a “Significant Weather Advisory”.

The wind criteria for issuing a Severe Thunderstorm Warning will remain 58 mph (50 knots).

In CR, previous participating NWS weather forecast offices included Dodge City, Goodland, Topeka and Wichita, Kansas; Hastings, Nebraska; Kansas City and Springfield, Missouri. Participation in the region-wide project will include 38 offices in Colorado, Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Wisconsin and Wyoming. For Western Region, this will include offices in Arizona, California, Idaho, Montana, Nevada, Oregon, Utah, and Washington.

If feedback in this large area over the next year remains positive, it is expected that the change to one inch hail criterion for severe thunderstorm warnings will be expanded nationwide.