Stacie HanesNOAA NWS Gray ME Jim HayesNOAA NWS Mount Holly NJ 12 th Northeast Regional Operational Workshop November 35 2010 Outline Overview of the event Review of the structure and evolution of a Norwegian and a ShapiroKeyser cyclone ID: 255211
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Examining the Damaging New England Windstorm of 25-26 February 2010 as a Shapiro-Keyser Cyclone
Stacie Hanes/NOAA NWS Gray ME
Jim Hayes/NOAA NWS Mount Holly NJ
12
th
Northeast Regional Operational Workshop
November 3-5, 2010Slide2
Outline
Overview of the event
Review of the structure and evolution of a Norwegian and a Shapiro-Keyser cycloneOverview of the synoptic setup prior to the damaging windsUse of observational and model data to identify the structure of Shapiro-Keyser cycloneSlide3
Brief overview of the event
East to northeast winds gusted as high as 94 mph during the late evening and overnight of 25-26 Feb 2010
The strongest gusts occurred with the passage of a surface troughSignificant damage occurred across southeast New Hampshire and southwest and central Maine
This wind event caused the second largest number of power outages ever in New HampshireSlide4
Brief overview of the event
Three peak wind gusts of over 90 MPH were recorded during this event
Portland ME (PWM) had its highest wind gust ever recorded. It may have been higher, but the power failed at the ASOSSlide5
The highest wind speeds occurred with surface trough between 1100 PM and 200 AM across southeast New Hampshire and southern Maine.
Destructive winds from the east or northeast are fairly rare in northern New England, especially at night.Slide6
Was this the result of a warm front/occluded frontal passage, or something else?Slide7
Norwegian Cyclone Model
Typically the strong winds occur in the warm sector in this cyclone model or on the back side in the cold air advectionSlide8
Norwegian Cyclone Model
This cyclone model could account for stronger winds reaching the surface in the “warm sector”, but the low levels appear
too stable to allow turbulent mixing in the “cool sector”
This model does not explain the destructive winds on the cold side of the warm/occluded front Slide9
Shapiro-Keyser Model
Open wave
(similar to the Norwegian cyclone model
Frontal fracture
(T bone frontal structure)
Bent-back front
–
strong winds on the cold side of the warm front
Warm seclusion
– evaporative cooling/descent can allow an eye-like feature to develop.Slide10
Shapiro-Keyser model
Typically develops as a marine cyclone
Generally forms in large scale confluence and a high zonal index flowCharacterized by a
strong warm front
, weak cold front and T bone frontal structureSlide11
Models were fairly close concerning the overall sequence of events. The 1200 UTC 25 Feb 2010 NAM model solution is examined.
So now that we have an idea of how the storm should look…what did the models show?Slide12
1200 UTC 25 Feb 2010 NAM - 0600 UTC (left) and 0900 UTC (right)Slide13
1200 UTC 25 Feb 2010 NAM - 0000 UTC (left) and 0300 UTC (right)Slide14
1200 UTC 25 Feb 2010 NAM - 0600 UTC (left) and 0900 UTC (right)Slide15Slide16
Bottom line
The NAM was forecasting a highly anomalous event for northern New England
Many forecast parameters showed departures of 4 to 5 standard deviationsMain time frame was 0300 UTC to 0900 UTC for the forecast areaSlide17
Examining the Shapiro-Keyser cyclone environment using observational toolsSlide18
0015z 26 Feb 2010 IR image – the cyclone is the in bent-back front stage (Stage III)Slide19
0000 UTC 26 Feb 2010 GYX observed sounding
The depth of the mixed later is unusual for an easterly flow at nightSlide20
0255 UTC 26 FEB 2010 AMDAR descent sounding at BOS
60 knot wind at 1210 ft.Slide21Slide22
0415z 26 Feb 2010 IR image – the cyclone is the in warm seclusion stage (Stage IV)Slide23Slide24Slide25Slide26Slide27
Summary
Damaging winds occurred in northern New England during the late evening of 25 February 2010 and the early morning of 26 February 2010
Damage was caused by east to northeast winds during an unusual time
A few locations had maximum wind gusts over 90 MPH
PWM had its high wind gust ever before the ASOS power failed
The damaging winds occurred in the cold air ahead of the warm front, which suggests a Shapiro-Keyser cyclone