impact of ocean observations on hurricane irene intensity forecasts
TRANSCRIPT
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IMPACT OF OCEAN OBSERVATIONS ON HURRICANE IRENE INTENSITY FORECASTS
S. Glenn, O. Schofield, J. Kohut, H. Roarty, J. Kerfoot, M. Oliver, H. Seim, G. Seroka,
L. Palamara, L. Bowers, R. Dunk, M. Crowley,
W. Boicourt, W. Brown, L. Atkinson
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Total inches of rainfall
0 32
Aug 20-29
• First tropical storm to threaten New York City since Hurricane Gloria in 1985
• Flooding records broken in 26 rivers • Caused at least 56 deaths • Damage nearly $8 billion
Hurricane Irene
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Hurricane Irene in the News: • Track accurately forecast days in advance. • Intensity was over-predicted.
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U..
Cape Cod
Cape Ha)eras
NJ
MA CT
VA
DE
NY
NC
RI
MD
PA 10 States
MIDDLE ATLANTIC REGIONAL ASSOCIATION COASTAL OCEAN OBSERVING SYSTEM
1000 km Cape to Cape
Gliders Forecasts L-‐Band X-‐Band CODAR
Regional Association – 2004
Regional Coastal Ocean Observing System – 2007
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39.5N 73W Surface Current Time Series Total Current Near-Inertial Current
Wave & Wind Direction Time Series
Hurricane Irene
Eye Passes over NJ mid-day on Aug 28
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39.5N 73W Surface Current Time Series Total Current Near-Inertial Current
Wave & Wind Direction Time Series
Hurricane Irene
Eye Passes over NJ mid-day on Aug 28
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Hurricane Irene Surface Current Wavelet Analysis
Direct Wind Forcing Inertial Response
Aug 27 Aug 28 Aug 29 Aug 30 Aug 31 Sep 01 Frontside Eye Backside Inertial Inertial Inertial
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Operational Global SST Products
Real-Time Global (RTG) Smooth Data in Space
Short Term Prediction Research & Transition Center (SPoRT) Smooth Data in Time
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MARACOOS SST Product for Offshore Wind
MARACOOSRegional SST = Coldest Dark Pixel Composite of Local AVHRR + SPoRT + RTG
Real Time Global SST Regional
Coldest Pixel SST
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SST Difference
Global SST
Regional SST
Post-Hurricane Irene Sea Surface Temperatures
But when did the 6C - 8C Cooling occur?
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Two Gliders Deployed by MARACOOS
in Hurricane Irene
RU16 • Deployed for EPA. • Map bottom dissolved oxygen. • Provided data on mixing during storm.
RU23 • Deployed for MARACOOS. • Map subsurface T/S structure for fisheries. • Damaged early - drifter • Recovered by fisherman • Provided data on inertial currents during storm.
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14 33
29
105
60
salinity
% oxygen
temperature 55
55
0
0
55
dept
h de
pth
dept
h
8/12 9/07 date
26 0 Hurricane Irene Hurricane Irene
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Temp. Vert. Vel. Temp. Vert. Vel. Temp. Vert. Vel.
RU16 Temp. Section
Upcast Downcast
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For Each 2-hour Segment: 1) Calculate the Average Temperature Profile 2) Calculate the Vertical Velocity Standard Deviation Profile and Smooth Vertically.
Pre-Irene During Irene Post-Irene
Temp S.D. w’
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Time History of Mixing During Irene: Profiles of the Standard Deviation Vertical Velocity Profile
Time Progresses from Red to Blue
Eddy viscosity
Linear
Linear * Exponential Decay
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Hurricane Irene Currents: Glider Depth Average, CODAR Surface Layer and Calculated Bottom Layer
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Glider RU16
Thermocline Depth
Surface Temp
Max S.D. w’
Max S.D. w’ Depth
Glider, CODAR & Calculated Bottom Currents
NDBC Waves Bottom Orbital Velocity
NDBC Winds
MARACOOS Network Observations: Hurricane Irene
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35
45
55
65
75
85 W
ind
Spee
d (k
ts)
Date
Maximum Sustained Wind Speed (10m)
NHC Best Track
NHC Forecast
RU-WRF Atmospheric Forecast Model
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NHC Best Track
Even coupled models (e.g. HWRF) overpredicted Irene
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Hurricane Irene SST Sensitivity Hindcast
Maximum Wind Speed Skill Score
Official Forecast
Warm SST Hindcast
Warm SST + OML Model
Hindcast
Cold SST Hindcast
RMS Error (knots) 9.43 7.13 7.09 3.61
Global Warm SST Regional Cold SST
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Wind Speed Error Date/Time (UTC)
NHC Forecast
Warm (RTG only)
Warm (RTG only, OML Model)
Cold “Update” (AVHRR)
27/1200 5 -‐17.22 -‐17.23 -‐6.17 27/1800 10 4.1 4.2 5.88 28/0000 10 1.39 -‐2.14 3.96 28/0600 5 -‐1.2 -‐1.04 -‐1.21 28/1200 15 2.39 4.79 0.5 28/1800 15 4.97 3.51 -‐2.67 29/0000 15 3.62 1.93 -‐0.89 29/0600 10 10.48 9.84 4.52
Sum of Squares 800 457 452 118 RMSE 9.43 7.13 7.09 3.61
Hurricane Irene Conclusions: • U.S. IOOS interactive observatory network closes a gap in storm science.
• Surface layer cooling and deepening occurs rapidly when potential for mixing between surface and bottom boundary layers is greatest.
• Cooler sea surface temperatures reduce hurricane forecast intensities.
• U.S. IOOS is helping (HFIP) produce better hurricane forecasts now.
Hurricane Irene demonstrates the value of U.S. IOOS as designed: • A multi-agency supported NOPP-style partnership activity. • Make Observations > Advance the Science > Improve the Forecasts. • Support societal needs.