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2011 - Mid-Atlantic Severe Storm Thread


Kmlwx

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I notice that DOX and AKQ radar's have the notation "THE [stationID] RADAR HAS BEEN PUT INTO CONVECTIVE ZR RELATIONSHIP."

Can someone explain what this means? I assume it's to help measure more accurately the estimated rainfall, but I'd love to know how.

Thanks!

Z-R Relationship a mathematical equation that converts radar-measured reflectivity to an estimated rainfall rate. The reflectivity factor (Z) is related to both the drop-size distribution and the 6th power of the drop diameters. However, the radar only measures reflectivity, not the drop-size distribution. Hence, the drop-size distribution must be assumed and can be wrong. Unfortunately, different drop-size distributions can produce the same reflectivity factor but have markedly different rainfall rates. For example, many small drops can produce the same reflectivity as one large drop; however, the rainfall rate from the small drops is very different from the one large drop.

The equation is Z = aR^b where a and b are constants. The constants are not always the same for every situation, though. Tropical rainfall has different a and b coefficients than drier midlatitude storms, based on the drop-size distributions. If you google "Z-R relationship" you'll get a lot of good stuff.

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Maybe a nice view from the Bay... the cell that OEM mentioned in the General Disc. thread:

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE MOUNT HOLLY NJ

239 PM EDT WED MAY 18 2011

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* TORNADO WARNING FOR...

WESTERN TALBOT COUNTY IN EASTERN MARYLAND...

SOUTHWESTERN QUEEN ANNE'S COUNTY IN NORTHEAST MARYLAND...

* UNTIL 330 PM EDT

* AT 235 PM EDT...LOCAL FIRE DEPARTMENT PERSONNEL REPORTED A

TORNADO NEAR OXFORD...OR 8 MILES SOUTHWEST OF EASTON...MOVING

NORTH AT 25 MPH.

THERE WAS A TORNADO TOUCH DOWN OBSERVED EARLIER NEAR ISLAND CREEK.

* THE TORNADO WILL BE NEAR...

9 MILES EAST OF TILGHMAN ISLAND BY 250 PM EDT...

ST. MICHAELS BY 255 PM EDT...

COPPERVILLE AND TALBOT BY 300 PM EDT...

GRASONVILLE BY 320 PM EDT...

CHESTER BY 325 PM EDT...

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Under a tornado warning for second time today...

TORNADO WARNING

MDC005-025-182045-

/O.NEW.KLWX.TO.W.0065.110518T2010Z-110518T2045Z/

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC

410 PM EDT WED MAY 18 2011

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A

* TORNADO WARNING FOR...

BALTIMORE COUNTY IN NORTHERN MARYLAND...

HARFORD COUNTY IN NORTHERN MARYLAND...

* UNTIL 445 PM EDT

* AT 410 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A

SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR MIDDLE

RIVER...MOVING NORTHWEST AT 25 MPH.

* LOCATIONS IMPACTED INCLUDE...

WHITE MARSH...

PERRY HALL...

CARNEY...

KINGSVILLE...

PLEASANT HILLS...

FALLSTON...

JARRETTSVILLE...

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