methods datasets mark demaria and john a. knaff noaa/nesdis - regional and mesoscale meteorology...
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Methods
Datasets
Mark DeMaria and John A. Knaff NOAA/NESDIS - Regional and Mesoscale Meteorology Branch, Fort Collins, CO
Andrea B. Schumacher CIRA - Colorado State University, Fort Collins, CO
Charles R. Sampson - Naval Research Laboratory, Monterey, California
Edward M. Fukada - Joint Typhoon Warning Center, Pearl Harbor, Hawaii
Chris A. Sisko and David P. Roberts - National Hurricane Center, Miami, Florida
Katherine A. Winters - Patrick AFB, Melbourne, Florida
Harold M. Wilson – Fleet Weather Center, Norfolk, Virginia
Introduction
An Objective Aid for DoD Base Preparations in Advance of Tropical CyclonesAn Objective Aid for DoD Base Preparations in Advance of Tropical Cyclones
Introduction
Table 1. A catalog of TC-CORs system utilized to take action under a defined set of storm parameters including maximum sustained winds and duration.
The Department of Defense uses a Tropical Cyclone Conditions
of Readiness (TC-CORs) system to prepare bases and evacuate
assets and personnel in advance of adverse weather associated
with tropical cyclones (TCs). TC-CORS are recommended by
weather facilities either on base or at central sites and generally
are related to the timing and potential for destructive (50-knot)
sustained winds. Recommendations are then considered by base
or area commanders along with other factors for setting the TC-
CORs. Ideally, the TC-CORs are set sequentially, from TC-COR
IV (destructive winds within 72 hours) through TC-COR III
(destructive winds within 48 hours) and TC-COR II (destructive
winds within 24 hours), and finally to TC-COR I (destructive
winds within 12 hours) if needed. Each TC-COR, once set,
initiates a series of preparations (Table 1). As illustrated,
preparations for TC-COR IV can be as unobtrusive as obtaining
emergency supplies while preparations leading up to TC-COR I
are generally far more costly, intrusive and labor intensive
activities.
Note that east of the Dateline the rules are generally called
Hurricane Conditions of Readiness (HURCONs) while the same
rules are called Tropical Cyclone Conditions of Readiness (TC-
CORs) at bases west of the Dateline.
TC-COR Definition Preparedness Examples
IV 50-kt sustained winds possible within
72 hours
Obtain flashlight with extra batteries,
snacks, first aid supplies, bottled
water
III 50-kt sustained winds possible within
48 hours
Clean up around house, pick up loose
items
II 50-kt sustained winds anticipated
within 24 hours
Secure outdoor property including
picnic table, barbeque grill
I50-kt sustained winds anticipated within 12 hours
Schools close, fill available containers
with water
I-CAUTION34-49 kt occurring and are expected to reach 50 kt within 12 h
All outdoor activities except in
support of urgent military missions
discontinued
I-EMERGENCY 50-kt sustained winds occurring All outside activity prohibited
I-RECOVERY 50-kt sustained winds no longer
occurring
No outdoor activity authorized except
by pre-designated emergency crews
STORM WATCH Still a possibility of danger Normal activity resumes 2 h after
declaration.
ALL CLEAR Local recovery operations complete Be alert to possible damage and
hazardous conditions on roads, etc.
Tropical Cyclone Conditions of Readiness Table
Datasets
Military Base Cases 50-kt sustained wind
events
Andersen Air Force Base 11 2
Yokosuka Naval Base 18 2
Kadena Air Base 19 3
Yokota Air Base14
0
Misawa Naval Base2
0
Atsugi Naval Air Facility 5 0
Sasebo Naval Base 6 0
Iwakuni Marine Corps Air Station 4 0
Patrick Air Force Base 15 3
Norfolk Naval Base 17 2
Stennis Space Center 1 1
Mayport Naval Station 1 0
Table 2. A catalog of TC-CORs system utilized to take action under a defined set of storm parameters including maximum sustained winds and duration.
The forecast and best track data used for this study are taken
from the Automated Tropical Cyclone Forecasting System
(ATCF; Sampson and Schrader 2000) operational archives at
the NHC and JTWC. There are 113 operational TC-COR cases
(where a tropical cyclone approached close enough to a base
to investigate TC-CORs) from tropical cyclone passages in the
TC-COR database, and it includes 79 cases from 8 bases in
the western North Pacific, and 34 cases from four bases along
the Eastern Seaboard and in the Gulf of Mexico (Table 2).
Tropical Cyclone Forecasting Table
MethodsThe same sample of Atlantic tropical cyclones making landfall
along the U.S. mainland from 2004 to 2010 used in
Schumacher et al. (2010) was used here. Following their
methodology, 64-kt wind speed probabilities were computed at
12, 24, 48 and 72 hours prior to the arrival of the 64-kt winds to
correspond to the time criteria for TC-COR settings I, II, III, and
IV, respectively. Wind speed probabilities were generated
using the 2010 developmental version of the Monte Carlo Wind
Speed Probability (MCWSP) product. Locations along the U.S.
mainland coast where near-surface winds met or exceeded 64
knots were determined from tropical cyclone positions and
radius of 64-kt winds (R64) recorded in the ATCF.
Working under the assumptions that 1) missed TC-CORs can
have extreme negative consequences (e.g., loss of life) and
2) false alarms are also costly, a selection scheme for our
first-guess TC-COR probability thresholds was specified so
that 1) POD ≥ 0.99 and 2) FAR is minimized; implying the
cost-to-loss ratio is very small (Wilks 2006; pp 321-324). The
thresholds that we derived are shown below. These
thresholds appear at first glance to be quite low, but they are
defined to minimize the missed cases (POD ≥ 0.99). If it is
acceptable to miss 50-kt wind events (i.e., the cost-to-loss
ratio was close to one), these thresholds could be raised to
minimize the FAR and improve statistical skill scores (e.g.,
Peirce’s Skill Score or Threat Score) discussed in Wilks
(2006), but would increase the possibility of very costly
misses.
Figure 1. The aftermath of typhoon Songda after hitting Okinawa in 2011.
Experimental TC-COR Settings
• Uses cumulative 50-kt wind probabilities
• Thresholds based Atlantic Hurricane Watches/Warnings
• Strategic guidance for onset of 50-kt winds
TC-COR
4
3
2
1
Threshold Probabilities
5%
6%
8%
12%
Forecast Lead
72 H
48 H
24 H
12 H
Results and FindingsResults and Findings
NEED SHORT PARAGRAPH HERE
Figure 2. Objective aid and Operational TC-COR settings for all events with elevated winds. Quartiles shown as thick bars, extremes shown as thin bars. Numbers of cases for COR 1, 2, 3, 4 are 32, 46, 52, 59, respectively. Some of the largest differences are due to base considerations (e.g., keeping a COR 3 up in preparation for the next TC).
TC-COR Aid Timing
The TC-COR aid IV, III, II, and I times. Box indicates 1st and 3rd quartiles,
whiskers indicates entire range of cases. Number of cases is 33, 43, 53, 54 for
IV, III, II and I, respectively, from twelve military bases in Pacific and
Atlantic.
Sensitivity Analysis
Doubling thresholds improves TC-COR III and IV Peirce’s Scores (1=perfect,
0=no skill), but reduces forecast lead times (~7 hours for TC-COR IV) and
misses a few cases. CNMOC DOO suggests adding “Low”, “Medium”, “High”
confidence. Current thresholds are “Low” confidence by design.
Figure 6. (Above) Percentage of lead times reduced (top) and the average number of hours the lead time was delayed for all the cases (bottom) when the wind probability thresholds associated with the TC-CORs were doubled.
ReferencesReferencesDeMaria, M. , J .A. Knaff, R. Knabb, C. Lauer, C. R. Sampson, and R. T. DeMaria, 2009:A new
method for estimating tropical cyclone wind speed probabilities, Wea. Forecasting, 24, 1573-
1591.
Sampson, C. R., and A. J. Schrader, 2000: The Automated Tropical Cyclone Forecasting System
(Version 3.2). Bull. Amer. Meteor. Soc., 81, 1131-1240.
Schumacher, A.B., M. DeMaria, J. A. Knaff, C. R. Sampson and D. Brown, 2010: Objective
Tropical Cyclone Warning Guidance Using Monte Carlo Wind Speed Probabilities, 29th
Conference on Hurricanes and Tropical Meteorology, 10-14 May 2010, Tucson, AZ.
Wilks, D. S., 2006: Statistical Methods in the Atmospheric Sciences. 2nd ed. Academic Press,
467 pp.
Acknowledgements
Poster created by Ms. Laurel Kessler of CIRA