Heavy Rainfall Threatening The Mid-Atlantic Region! (credit: Meteorologist Sheldon Kusselson)9/27/2016  DISCUSSION: If you live in the Mid-Atlantic portion of the United States (centered on the Washington DC area), be prepared for a heavy rain (and possible flooding) event, even though it has been dry for the past month. Moisture coming from all over the place at different levels of the atmosphere and you can take note with this moisture analysis from different polar and geostationary satellites.
To learn more about other high-impact weather events from across North America, be sure to click here! ~Meteorologist Sheldon Kusselson
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 DISCUSSION: On September 18, 2016, the National Weather Service (NWS) Louisville, Kentucky forecast office released an Area Forecast Discussion at 3:18 p.m. EDT, which forecasted a potential isolated shower/sprinkle for far eastern parts of the state. Now, you often hear weather forecasters use the term “isolated showers”. But, what exactly does the NWS consider “isolated”?
A shower or thunderstorm that is “isolated” refers to rainfall/thunderstorms that will potentially cover approximately 10%-20% of a county viewing area or region. More specifically, very few locations will possibly receive rainfall while majority of the viewing area might remain mostly dry of precipitation. If a forecast anticipates isolated showers/thunderstorms, then a meteorologist will often highlight more specific locations (i.e. small cities, neighborhoods, small towns) that may receive rain or thunderstorms. The NWS Louisville forecasters illustrated the perfect definition of “isolated” showers by exhibiting radar-estimated rainfall amounts for two separate isolated shower systems (radar-estimated rainfall amounts can vary from actual ground rainfall estimates). The blue-green coloring on the radar imagery (above) displays the sparse regions that received rainfall at 8:37 p.m. EDT on September 18, 2016. In the left-most image, the neighboring areas located east of Green Grove received a maximum radar-estimated rainfall amount of 1.3 inches. The right-most radar imagery specifies a radar-estimated amount of 0.8 inches in a secluded location just north of Nonesuch, Kentucky. Therefore, only these two areas received “isolated” showers since the precipitation coverage occurred in a small vicinity of the state. To learn more about other high-impact weather events from across North America, be sure to click here! ~Weather Forecaster Aisha Murphy DISCUSSION: On September 1, 2016, WCNC (Charlotte, NC) Chief Meteorologist Brad Panovich acknowledged a peculiar feature inside of Hurricane Hermine while using the ZDR Dual-Polarization Differential Reflectivity Doppler Radar. Meteorologists operate Doppler Radar (RAdio Detection And Ranging) to detect precipitation, thunderstorms and other weather characteristics. It helps forecasters to predict tornadoes and pinpoint the exact location of precipitation. Dual-polarization radar exhibits unique abilities that allow it to distinguish precipitation from non-meteorological objects such as insects, birds, ground clutter and debris. The radar transmits pulses that are oriented in the vertical and horizontal directions. Once the pulses hit an object, it returns two-dimensional information back to the radar. Differential reflectivity (ZDR) is utilized to identify the shape and size of an object. It can detect airborne tornado debris, hail, storm updrafts and rotation. Thunderstorms accompanied with deep rotating updrafts are often a good indication of storm-producing tornadoes. The Dual-Polarization radar image (below) detected a cluster of objects that was situated in the core of the northeastern part of the hurricane’s eye (i.e. the center of the tropical cyclone). The eye is the region of calm winds (less than or equal to 15 mph), which dynamically organizes beneath a vacuum of sinking air that is characterized by pleasant weather conditions. Also, the eye is encircled by an eye-wall, which is composed of strong-to-severe thunderstorms whose impacts often consist of heavy rainfall and excessively strong winds. Simultaneously, Hurricane Hermine was drifting north-northeast at approximately 14 mph while maintaining maximum sustained wind speeds of up to 80 mph. Birds often travel inside of hurricane eyes to avoid the devastating winds which are situated within and beyond the eye-wall. Inside the eye of Hermine, a bird flock attempted to seek refuge in the core of this storm. More interestingly, the flock migrated in the same direction as the hurricane was moving just to survive throughout the duration of the storm. Nonetheless, this isn’t the first time a Dual-Polarization radar detected birds inside of a hurricane. In July 2014, the University of Alabama Huntsville Severe Weather Institute Radar and Lightning Laboratories used ZDR and Dual-Polarization reflectivity to distinguish birds versus hurricane precipitation within Hurricane Arthur. In the eye of Arthur, scientists concluded that a pink cluster of non-meteorological objects on the radar was a flock of birds seeking refuge. Similarly, as Chief Meteorologist Brad Panovich reminisced on the Hurricane Arthur case, he used radar reflectivity and ZDR to comparatively identify that a flock of birds were present on the radar within Hurricane Hermine. To learn more about other high-impact weather from across North America, be sure to click here! @Meteorologist Aisha Murphy  
DISCUSSION: As what still remains to be Post-Tropical Storm Hermine continues to slowly travel northward just offshore from the Mid-Atlantic coastline, many questions have surfaced amongst people in the respective states which have been, are, or still still remain at least partially in this storm's path. The leading questions concerns the future track of this storm based on many meteorologists explaining the high-degree of variability which currently still exists amongst the various possible trajectories this post-tropical (and possibly soon to once again be tropical) system may take in the not-too-distant future (i.e., over the next 48 to 72 hours). Barring this high degree of uncertainty tied to the forecast at this time, there still remains a to be a legitimate reason for this uncertainty (as illustrated by the animated graphic below). More specifically, this animated graphical rendering of the current larger-scale synoptic flow regime in place across the Eastern United States, the western Atlantic Ocean, and parts of Atlantic Canada reflect the sheer complexity of the current weather pattern which will directly govern the future track of this system.
To be more precise, here is a quote from the original post written by Meteorologist Jeff Berardelli which provides a perfect explanation for the future of this storm. "Hermine is going to merge with another weather system which will re-energize and stall Hermine. The weather system it will merge with can be looked at as a weak front at the surface, an upper level low aloft and essentially a piece of the jet stream. Once Hermine merges and then emerges off the Virginia coast it will move over the very warm Gulf Stream waters. High pressure will build southward into New England and trap Hermine. So what you have is a storm of hurricane strength sitting just offshore of New Jersey/ Del Marva Sunday, Monday, Tuesday and perhaps longer. The coast will likely see winds gusts near hurricane force Sunday late-Monday (depending on how close the storm meanders), offshore waves of 25-35 feet and the worst impact of all will be significant, and potentially record coastal flooding from Southern NJ south to Virginia. Why potentially record setting? Well when you have a storm of hurricane force barely moving for 3 days you continually pile up the water against the coast, back bays, nooks and crannies. Will the coastal flooding be equivalent to Sandy? No, not quite. But might it be the worst coastal flooding residents from South Jersey to Virginia have ever seen. Remember Sandy's worst coastal flooding was mainly from Atlantic City northward. Although we can't pinpoint the exact location of the impacts yet it does look like the coastal flooding will extend much further south." Collectively, it reflects one of the more complicated forecast evolutions which a meteorologist anywhere will ever contend with and will eventually make for another avenue of excellent research work and future study. To learn more about other high-impact weather educational topics within meteorology, be sure to click here! @Meteorologist Jordan Rabinowitz |
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