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The Operational Impact of QuikSCAT Winds at the NOAA Ocean
Prediction Center Joe Sienkiewicz NOAA Ocean Prediction CenterJoan
Von Ahn STG/NESDIS ORAOutlineOPC overviewImpact Warnings and
FeaturesHurricane Force WindsSST impacts on near surface
windsSummary and Recommendations
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OPC ResponsibilityWind Warning CategoriesGALE 34-47 knotsForce
8/9STORM 48-63 knotsForce 10/11HURRICANE FORCE - 64 knots and
greater Force 12
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Wind speed (knots)
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Warning ImpactPercent Change in Short-Term Warning Decisions by
OPCTimelinesaddedAdditionaltrainingForecaster queryForecaster input
onlyInterpreted forecaster comments
Chart2
3022
75
54
1010
Atlantic
Pacific
Period of Study
Percent Increase
Sheet1
AtlanticPacific
Fall 20023022
Spring 200375
Fall 200354
Winter 20041010
Sheet1
00
00
00
00
Atlantic
Pacific
Period of Study
Percent Increase
Sheet2
Sheet3
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Winter 2004 (Feb 15 to Mar 15)When QuikSCAT was available,
changes were made to:68 % of the events in the Atlantic 50% of the
events in the PacificEvent- Lows, Highs and Wind areas (speed and
aerial extent)Atlantic
Pacific
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Hurricane Force WindsQuikSCAT able to distinguish between STORM
and HURRICANE FORCE winds
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OOCL AmericaM/V Explorer
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OOCL AmericaPacific - Jan 2000350 containers lost overboard 217
crushed or bent out of usable condition.
Vessel lost power for a short periodand took several severe
rolls.
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Hurricane Force CyclonesWhat have we learned?Winter events
October through March (April)Most frequent Atlantic (January);
Pacific (December)Minimum SLP (avg. 965 to 970 hPa) Minimum SLP -
larger range in AtlanticExplosive deepeners Western portion of
basins (most frequent); preferred tracksShort lived (less than 24
hours) (avg. lifecycle 5 days)Shallow warm core seclusionWind max S
to SW of lowMost difficult to forecast at day 4 forecast time over
North PacificLess than 10 % forecast 4 days in advance!! Number of
HF Cyclones observed
Period of
StudyAtlanticPacific2001-200222152002-200323222003-20041522
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Composite of maximum winds (knots)Pacific (11 cyclones) Atlantic
(5 cyclones) Composite of QuikSCAT winds for 11 North Pacific and 5
North Atlantic HF storms. This plot shows the distribution of
maximum winds as observed by QuikSCAT for all cyclones in the
composite. HF winds are Red, Storm -Yellow and Gale Green. HF
FORCESTORMGALE
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SST Impacts on Near Surface Winds
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12.5 km QuikSCAT3-day GOES SST Composite
25 km QuikSCATWind speed difference (GFS 10m-QuikSCAT)
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GFS 10 WInds12.5 km QuikSCAT
Bias corrected 10m Winds Wind speed difference (knots) (GFS
10m-QuikSCAT)
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Eta 10m GFS 10m
GFS 9950 Sigma
30 day avg. diff11/05/04Model Winds - QSCATVery Unstable
PBL975-skin < -4
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30 day avg. diffModel Winds - QSCAT Very Stable PBL 975-skin
> 4Eta 10m GFS 10m
GFS 1st Sigma
Eta 10m GFS 10m
GFS 1st Sigma
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SST impacts on Wind Field
Due to QuikSCAT OPC forecasters are more conscious of underlying
SST on near surface winds
(always knew an impact but forecasters can now see it)
Forecaster toolsmodel soundingsstability indicesmix of 1st sigma
and 10m windswind speed difference fields
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QuikSCAT Rain QuandryJanuary 4, 2005
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12.5 km QuikSCATSSM/I Wind Speeds
25 km QuikSCAT SSM/I Rain Rate
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12.5 km QuikSCATQuikSCAT Ambiguities
25 km QuikSCAT SSM/I Rain RateThere are times when our
forecasters do not know what to believe!
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SummaryImpact - Significant Cultural change to ocean analysis
and forecasting within OPC10 % Wind Warnings determined by
QuikSCATAssessment of features more accurateAbility to assess
initial numerical model conditions
Can differentiate between significant and extreme winds Storm
versus Hurricane Force Significance of PBL stability on near
surface winds
QuikSCAT winds have changed the way we do business
Precip QuandryAt times just do not know impact on wind
retrievals
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Recommendations(for future instruments)
Large swath width Independent rain measurement Ability to
quantify impact of rain Large retrievable wind range (0 to
Hurricane Force) 12.5 km resolution or better Reduced land mask
(less than 30 km) Minimum 4 looks per day per ocean (from
operational platforms) Data access near-real time (1 to 1.5 hour
delivery after acquisitionno more) Available in forecaster
workstations in comprehensive form
These two composites show the maximum observed wind speed for
each 25 km spaced grid point. The south semicircle is clearly the
area preferred to observe HF winds. The cases contributing to these
composites consisted of open ocean examples well away from the
influence of land. There do appear to be some differences between
the composites with a strong hint of a well displaced occluded
frontal structure in the Atlantic composite with a large area
devoid of storm winds. There also is a hint of maybe two different
scales in the Atlantic composite with a minima of winds (sub Gale)
to the west of the center. The Pacific composite suggest a more
compact wind field with storm force fairly close into the center to
the north. We may indeed be seeing the evidence of inherent
differences between the evolution of Pacific vs. Atlantic extreme
storms. The Pacific jet structure seems to favor diffluent jets and
left front quadrant developments. This favors Norwegian type
cyclones that may indeed had a smaller inner core. The Atlantic
cyclone composite wind field is significantly more spread out with
a very clear signal of a Shapiro Keyser frontal structure. The
inner radius of inner winds are displaced about 120 nm to the south
of the center. The pacific inner core are only about 60 nm or less
from the cyclone center. Just food for thoughtmakes you wonder if
scale is working against us and may indeed be the contributing
factor to the difficulty of the models being able to forecast the
Pacific cyclones frequently.