2015 Atlantic Hurricane Season Birdseye Discussion #28

By: NCHurricane2009 , 11:49 PM GMT on June 20, 2015

...SATURDAY JUNE 20 2015 7:49 PM EDT...
The remnant surface low of former Tropical Storm Bill is moving eastward across the Ohio Valley...mid-Atlantic...and southern New England regions of the United States while embedded in the westerlies on the north side of the Atlantic surface subtropical ridge (marked by red-zig-zag line in the atmospheric features chart below). The remnant low is maintaining strength due to supportive upper divergence on the east side of a shortwave upper trough (marked by blue-dashed line just west of Bill). The ground over the Ohio Valley region has recently become soaked from frequent rains along the stalled frontal boundary presently over this region...and Bill has recently merged with this front. Therefore main threat from Bill's remnants over the next couple of days will be flash flooding potential across West Virginia...northern Virginia...southeastern Pennsylvania...Maryland...Delaware...and New Jersey where flash flood watches are currently in effect from the National Weather Service.

It is quiet elsewhere across the Atlantic tropics...

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1932Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperature isotherms at http://www.nhc.noaa.gov/satellite.php...the site from which the above thermo chart is generated from...are currently outdated. Therfore I have approximated the 26 deg C isotherm in the above chart using the sea-surface temperature maps available at www.wunderground.com/hurricane. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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1:25 AM GMT on June 22, 2015
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