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The Evolution of Predecessor Rainfall Events (PRE) with Tropical Cyclones Danny and Bill from the 2009 Season. Michael L. Jurewicz, Sr. WFO Binghamton, NY Northeast Regional Operational Workshop November 5, 2009 . AR TC Tracks and PRE Locations. All AR TC Tracks.
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The Evolution of Predecessor Rainfall Events (PRE) with Tropical Cyclones Danny and Bill from the 2009 Season Michael L. Jurewicz, Sr. WFO Binghamton, NY Northeast Regional Operational Workshop November 5, 2009
AR TC Tracks and PRE Locations All AR TC Tracks All AR PPTC Tracks; with PRE centroids (colored dots)
Conceptual Model: LOT PREs Ahead Of SR Or AR TCs UL Jet LL θe-Ridge Axis PREs See inset Mid-level Streamlines TC Rainfall Revised and updated from Fig. 13 of Bosart and Carr (1978) Representative TC Tracks
Brief History of Bill Himself • Bill was initially a Cape Verde tropical wave, which became a named storm on 15 August • From 19-23 August, Bill attained hurricane status well off the U.S. East Coast (briefly reached Category 3) • From 23-25 August, Bill transitioned to an extra-tropical system, as it recurved into the westerlies southeast of the Canadian maritime provinces
Afternoon Rainfall on 22 August Up to 7” (175 mm) rainfall
200 mb Height/Wind/PV, 22z, 22 August Height Rises / PV Destruction
Surface Analysis, 18z, 22 August Possible PRE
850 mb Moisture Transport Possible PRE
700 mb Heights, 925 mb Winds/Theta-E, at 21z, 22 August Near intersection of Bill’s moisture and pre-existing moist plume
Parcel Trajectories into Central New England Bill’s Track
Bill Summary • Bill fit into the AR track for potential PRE-producing systems • One main heavy rain episode took place on the periphery of Bill’s influence • Southern NH on 22 August • 4-7” (up to 175 mm) of rain fell within just a few hours, causing flash flooding • Transient nature of heavier rain bands precluded excessive rainfall/runoff problems elsewhere
Brief History of Danny Himself • Danny was initially a Cape Verde tropical wave, and took several days to become a named storm • Finally, on 26 August, it attained Tropical Storm status east of the Bahamas • From 26-29 August, Danny remained a Tropical Storm well off the Southeast U.S. coast • From 29-31 August, Danny weakened to a Tropical Depression, and ultimately transitioned to an extra-tropical system, as it recurved off the U.S. East Coast
Late Night/Early Morning Rainfall, 27-28 August 4-8” (100-200 mm) rainfall
700 mb Heights, 925 mb Winds/Theta-E, at 05z, 28 August Separate moist axis Axis of tropical moisture
Late Afternoon/Overnight Rainfall, 28-29 August Widespread 5-10” (up to 250 mm) rainfall
700 mb Heights, 925 mb Winds/Theta-E, at 03z, 29 August Tropical Moisture Axis
SB CAPE Analysis, 00z, 29 August Possible PRE
Surface Analysis, 00z, 29 August Possible PRE
Parcel Trajectories into the Mid-Atlantic Coastal Region Danny’s Track
Danny Summary • Danny fit into the AR track for potential PRE-producing systems • Two distinct heavy rain episodes took place on the periphery of Danny’s influence • Event that most resembled a PRE took place just offshore, 28-29 August • Heavy rain/flash flooding that occurred in the Baltimore area appeared to lack sufficient moisture contributions from Danny or jet interactions • Lack of a direct moisture connection with the TC, as well as a relatively cool stable air mass, seemed to protect much of the Northeastern U.S. from excessive rainfall