The Use of Ensemble and Anomaly Data during the 13-16 May 2006 New England Record Rain Event Neil A. Stuart Richard Grumm Walter Drag NOAA/NWS Albany, NY NOAA/NWS State College, PA NOAA/NWS Taunton, MA Northeast Regional Operational Workshop VIII Albany, NY 1 November 2006
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The Use of Ensemble and Anomaly Data during the 13-16 May 2006 New England Record Rain Event
The Use of Ensemble and Anomaly Data during the 13-16 May 2006 New England Record Rain Event. Neil A. Stuart Richard Grumm Walter Drag NOAA/NWS Albany, NY NOAA/NWS State College, PA NOAA/NWS Taunton, MA - PowerPoint PPT Presentation
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The Use of Ensemble and Anomaly Data during the 13-16 May 2006 New England Record Rain
Event
Neil A. Stuart Richard Grumm Walter DragNOAA/NWS Albany, NY NOAA/NWS State College, PA NOAA/NWS
Taunton, MA
Northeast Regional Operational Workshop VIIIAlbany, NY
1 November 2006
Overview – Heavy rain events studied
October 1996 > 12” of rain in part
of southern and eastern New England
Major flooding in eastern MA, NH and ME
Overview – Heavy rain events studied
October 2005 Phase I 8-12” of rain interior northeast U.S. and New England Major flooding in eastern NY, and much of western and
central New England
Overview – Heavy rain events studied
October 2005 Phase II 8-12” of rain for large part of New England Major flooding across the New England Region
Overview – Heavy rain events studied
May 2006 > 12” of rain in eastern New England Major flooding in eastern MA, NH and ME
Overview – Heavy rain events studied
June 2006 > 12” of rain in the interior northeast U.S. Major flooding in interior PA, NY
Overview
Compared May 2006 with 3 other cases Two large scale patterns identified that
support flooding warm season rains No cold season cases with snow melt
involved No weakly-forced, localized summer
time convective flood events Focus on widespread synoptic scale
events Newly developed forecast products to
evaluate heavy rain potential
Type A – Atlantic Flow MSLP and PW Anomalies
October 1996 May 2006
Type A – Atlantic Flow Wind Anomalies
October 1996 May 2006
Type B – Gulf/Tropical Origins Wind and PW AnomaliesOctober 2005 June 2006
One more important note about October 2005
Transition from Gulf/Tropical event to Atlantic flow event
Note the PW anomalies and timing of rainfall distributions
Some selected guidance products
Short Range Ensemble Forecast Probability of
2.00” of rain in 36 hours
Short Range Ensemble Forecast Probability of
2.00” of rain in 36 hours
Short Range Ensemble Forecast Probability of
2.00” of rain in 84 hours
Some selected guidance products
12Z 10 May 2006 SREF Plume Diagram
– Precipitation Accumulation for
Boston, MA
12Z 11 May 2006 SREF Plume Diagram
– Precipitation Accumulation for
Boston, MA
12Z 12 May 2006 SREF Plume Diagram –
Precipitation Accumulation for
Boston, MA
Conclusions 2 Types of events
Type A – Atlantic flow Upper system cut off from steering flow = slow
moving system Anomalously strong southeast low-level flow
– Anchored surface high pressure in SE Canada– Strong surface low pressure in Great Lakes or Ohio
Valley in weak steering flow– Extreme 850 hPa U and V wind anomalies (≥ |4SD| for
U, V or both directions) Anomalously high Precipitable Water values (≥
1.5SD) Persistent long-duration combination of extreme
low-level wind anomalies and Precipitable Water
Conclusions (cont.)
Type B – Gulf and Tropical Origins Slowly moving large scale upper trough approaching
from the Midwestern U.S. Smaller short wave(s) of energy track in weak flow on
eastern side of upper trough Extreme S to SW 850 hPa wind anomalies associated
with smaller short wave(s) (≥ 4SD V winds) Extreme Precipitable Water anomalies (≥ 1.5 SD, but
often ≥ 2.0 SD with tropical cyclones or remnants) Often associated with tropical system or its remnants
in the late summer and autumn
Conclusions (cont.)
Clues in Medium Range and Short Range Ensemble Forecast Model Guidance (MREF and SREF) Co-location of anomalously high precipitable water and 850
hPa wind maximum Probability for 2.00” of rain and spread for 36 hours or time
period that spans the entire event Areal extent of 2.00” probability contour less important as the
fact it exists Any probability above 50% lends very strong confidence of 2.00”
or more Can at least double local rainfall amounts depending on expected
intensity, duration and orography Spread shows # of members forecasting ≥ 2.00” – Accounts for
masking of areal extent in probabilities Plume diagrams - time sequence of QPF for each ensemble
member - affects confidence in QPF forecast Be careful to consider the NWP model characteristics – SREF
mainly NAM/WRF and MREF is GFS
Thank You!
Real-time anomalies, plumes and probabilities can be found at: Http://eyewall.met.psu.edu