Verification of Severe Weather Verification of Severe Weather Avoidance Plan (SWAP) Forecasts Avoidance Plan (SWAP) Forecasts for the New York Air Route Traffic for the New York Air Route Traffic Control Center (ARTCC) Issued by Control Center (ARTCC) Issued by

NWS CWSU Ronkonkoma, NYNWS CWSU Ronkonkoma, NY

Kirt SquiresKirt Squires

Kyle StruckmannKyle Struckmann

CWSU MeteorologistsCWSU Meteorologists

New York ARTCC (ZNY) AirspaceNew York ARTCC (ZNY) Airspace

What is SWAP?What is SWAP?

A program to ensure the safe flow of air A program to ensure the safe flow of air traffic when a significant number of jet traffic when a significant number of jet routes are impacted by weather or other routes are impacted by weather or other phenomena.phenomena.

Usually caused by convection.Usually caused by convection.

Convection does not have to be “severe” by Convection does not have to be “severe” by National Weather Service warning National Weather Service warning standards. standards.

Isolated ConvectionIsolated Convection

Aircraft can deviate around the cell without Aircraft can deviate around the cell without interfering with aircraft on nearby jet routes.interfering with aircraft on nearby jet routes.

Aircraft may be able to fly over low-topped Aircraft may be able to fly over low-topped convection.convection.

Clusters or Lines of ConvectionClusters or Lines of Convection

Often impact more than one jet route Often impact more than one jet route simultaneously.simultaneously.

Jet routes are often closed. Jet routes are often closed. Aircraft must be re-routed to different jet Aircraft must be re-routed to different jet

routes.routes. Arrival/departure delays increase.Arrival/departure delays increase.

Storms Close to NYCStorms Close to NYC

May impact most jet routes and TRACON May impact most jet routes and TRACON Gates.Gates.

Low-topped cells have as much impact as Low-topped cells have as much impact as high-topped cells.high-topped cells.

Very few ways in or out.Very few ways in or out. High impact on arrival/departure delays.High impact on arrival/departure delays. Example courtesy MITRE CAASD/FAA, Example courtesy MITRE CAASD/FAA,

June 16, 2008.June 16, 2008.

The SWAP StatementThe SWAP Statement

Issued daily at 15z (11:00 a.m. EDT) – or earlier if Issued daily at 15z (11:00 a.m. EDT) – or earlier if requested. April 15 – September 30, 2008.requested. April 15 – September 30, 2008.

SWAP is:SWAP is:– ““Not Expected” (0% chance of SWAP)Not Expected” (0% chance of SWAP)– ““Possible” (Greater than 0% but less than 50%)Possible” (Greater than 0% but less than 50%)– ““Probable” (50% or greater but less than 95%)Probable” (50% or greater but less than 95%)– ““Expected” (95% or greater)Expected” (95% or greater)

Followed by discussion SWAP start time, convective Followed by discussion SWAP start time, convective development and jet routes to be impacted.development and jet routes to be impacted.

SWAP Statement UsersSWAP Statement Users

Systems Command Center Systems Command Center

TMU/Area Supervisors TMU/Area Supervisors

Surrounding ATC Centers Surrounding ATC Centers

AirlinesAirlines

SWAP Forecast ProcessSWAP Forecast Process

Examine forecast models (GFS, NAM, RUC, Examine forecast models (GFS, NAM, RUC, etc.).etc.).

Consider dynamics, (instability, moisture Consider dynamics, (instability, moisture advection, topography, etc.).advection, topography, etc.).

Monitor Storm Prediction Center products.Monitor Storm Prediction Center products. Participate in Aviation Weather Center Participate in Aviation Weather Center

convective collaboration online chats.convective collaboration online chats.

SWAP Forecasting Process SWAP Forecasting Process (continued)(continued)

Determine when/where convection will start Determine when/where convection will start and how it will evolve.and how it will evolve.

Forecast location of convection in relation to Forecast location of convection in relation to jet routes.jet routes.

Also watch neighboring regions (i.e. Also watch neighboring regions (i.e. Cleveland ARTCC, Washington ARTCC, Cleveland ARTCC, Washington ARTCC, Boston ARTCC).Boston ARTCC).

Example SWAP Statement Example SWAP Statement (Possible)(Possible)

ZNY SWAP OUTLOOK FOR FRIDAY, JUNE 20TH, 2008ZNY SWAP OUTLOOK FOR FRIDAY, JUNE 20TH, 2008

SWAP IS POSSIBLE ANY TIME AFTER 18Z. SCT TS MAY DEVELOP SWAP IS POSSIBLE ANY TIME AFTER 18Z. SCT TS MAY DEVELOP INITIALLY OVER SE OH AND WV…IMPACTING J80/J6. THESE INITIALLY OVER SE OH AND WV…IMPACTING J80/J6. THESE STORMS WOULD MOVE INTO NRN VA AROUND 23Z AND AFFECT STORMS WOULD MOVE INTO NRN VA AROUND 23Z AND AFFECT J48/J75. TOPS TO FL350. A SECOND AREA OF SCT TS MAY J48/J75. TOPS TO FL350. A SECOND AREA OF SCT TS MAY DEVELOP OVER NRN PA/CENTRAL NY AROUND 19Z WITH TOPS DEVELOP OVER NRN PA/CENTRAL NY AROUND 19Z WITH TOPS TO FL350. THESE STORMS WOULD IMPACT J95/J36. THESE TO FL350. THESE STORMS WOULD IMPACT J95/J36. THESE STORMS MAY MOVE INTO OR REDEVELOP IN ERN ZNY AFTER STORMS MAY MOVE INTO OR REDEVELOP IN ERN ZNY AFTER 21Z…AND POSSIBLY IMPACT ANY/ALL JET ROUTES OUT OF 21Z…AND POSSIBLY IMPACT ANY/ALL JET ROUTES OUT OF NORTH AND WEST GATES.NORTH AND WEST GATES.

Verification: SWAP began at 1815z.Verification: SWAP began at 1815z.

Example SWAP StatementExample SWAP Statement(Probable)(Probable)

ZNY SWAP OUTLOOK FOR SUNDAY, JULY 6th, 2008ZNY SWAP OUTLOOK FOR SUNDAY, JULY 6th, 2008

SWAP IS PROBABLE AFTER 1700Z FOR THE FOLLOWING REASONS:SWAP IS PROBABLE AFTER 1700Z FOR THE FOLLOWING REASONS:

1. SCATTERED TS ARE EXPECTED TO FORM THIS AFTN ACROSS ZNY AND INTO 1. SCATTERED TS ARE EXPECTED TO FORM THIS AFTN ACROSS ZNY AND INTO WRN PA DUE TO A COMBINATION OF A WEAK SURFACE FRONT AND AN WRN PA DUE TO A COMBINATION OF A WEAK SURFACE FRONT AND AN UPPER LEVEL TROF APPROACHING FROM THE SSW. ROUTES FROM J60 – UPPER LEVEL TROF APPROACHING FROM THE SSW. ROUTES FROM J60 – SOUTH ARE MOST LIKELY TO BE IMPACTED.SOUTH ARE MOST LIKELY TO BE IMPACTED.

2. ADDITIONAL TS ARE EXPECTED TO FORM ACROSS WV AND WESTERN VA WITH 2. ADDITIONAL TS ARE EXPECTED TO FORM ACROSS WV AND WESTERN VA WITH IMPACTS LIKELY TO J6 AND J80.IMPACTS LIKELY TO J6 AND J80.

3. SCATTERED TS ARE EXPECTED TO FORM ACROSS MD…ERN VA AND ERN NC 3. SCATTERED TS ARE EXPECTED TO FORM ACROSS MD…ERN VA AND ERN NC WITH IMPACTS POSSIBLE TO ANY SRN ROUTE.WITH IMPACTS POSSIBLE TO ANY SRN ROUTE.

Verification: SWAP began at 1745z.Verification: SWAP began at 1745z.

Example SWAP Statement Example SWAP Statement (Expected)(Expected)

ZNY SWAP OUTLOOK FOR SUNDAY, JULY 27TH, 2008ZNY SWAP OUTLOOK FOR SUNDAY, JULY 27TH, 2008

SWAP IS EXPECTED AFTER 15Z. MAIN AREA OF TS WITH TOPS TO SWAP IS EXPECTED AFTER 15Z. MAIN AREA OF TS WITH TOPS TO FL370 IS EXPECTED TO DEVELOP BY 16Z OVER NEW ENGLAND, FL370 IS EXPECTED TO DEVELOP BY 16Z OVER NEW ENGLAND, ERN PA, NJ, SE NY, AND SWD ALONG THE EAST COAST TO NC. ERN PA, NJ, SE NY, AND SWD ALONG THE EAST COAST TO NC. BEFORE THAT, ISOLATED TS ARE PSBL OVER THE SAME AREA. BEFORE THAT, ISOLATED TS ARE PSBL OVER THE SAME AREA. TS WILL MOVE SLOWLY EWD THRU ZNY AIRSPACE AND NY/PHL TS WILL MOVE SLOWLY EWD THRU ZNY AIRSPACE AND NY/PHL TRACON AREAS THIS AFTERNOON AND EARLY EVENING TRACON AREAS THIS AFTERNOON AND EARLY EVENING BEFORE WEAKENING AROUND 02Z. DEVIATIONS ARE BEFORE WEAKENING AROUND 02Z. DEVIATIONS ARE EXPECTED ON ALL NY TRACON GATES AND ALL JET ROUTES EXPECTED ON ALL NY TRACON GATES AND ALL JET ROUTES J95/J75 AND WHITE/WAVEY DEPARTURES.J95/J75 AND WHITE/WAVEY DEPARTURES.

Verification: SWAP began at 1500z.Verification: SWAP began at 1500z.

ZNY CWSU SWAP Forecast ResultsZNY CWSU SWAP Forecast Results

SWAP is “Not Expected”SWAP is “Not Expected”– 65 Forecasts65 Forecasts– 64 Times SWAP did not occur64 Times SWAP did not occur– Percent of SWAP Implementation (POSI) = Percent of SWAP Implementation (POSI) =

1.5% 1.5%

ZNY CWSU SWAP Forecast ResultsZNY CWSU SWAP Forecast Results

SWAP is “Possible”SWAP is “Possible”– 55 Forecasts55 Forecasts– 19 Times SWAP Occurred19 Times SWAP Occurred– POSI = 34.5% POSI = 34.5% – Well within range of 0% < POSI < 50%Well within range of 0% < POSI < 50%

ZNY CWSU SWAP Forecast ResultsZNY CWSU SWAP Forecast Results

SWAP is “Probable”SWAP is “Probable”– 21 Forecasts21 Forecasts– 18 Times SWAP Occurred18 Times SWAP Occurred– POSI = 85.7%POSI = 85.7%– Also well within range of 50% <= POSI <95%Also well within range of 50% <= POSI <95%

ZNY CWSU SWAP Forecast ResultsZNY CWSU SWAP Forecast Results

SWAP is “Expected”SWAP is “Expected”– 20 Forecasts20 Forecasts– 19 Times SWAP Occurred19 Times SWAP Occurred– POSI = 95%POSI = 95%– Achieves goal of POSI >= 95%Achieves goal of POSI >= 95%

Only time SWAP did not occur was during Only time SWAP did not occur was during Tropical Storm Hanna. Likely due to low air Tropical Storm Hanna. Likely due to low air traffic volume.traffic volume.

Optimal POSI and Deviation From Optimal POSI and Deviation From Optimal POSIOptimal POSI

To produce a realistic verification scalar for the SWAP To produce a realistic verification scalar for the SWAP forecasts, we have chosen deterministic values of optimal forecasts, we have chosen deterministic values of optimal forecast goals for each category, called the Optimal POSI forecast goals for each category, called the Optimal POSI

(O-POSI).(O-POSI). – ““Not Expected”- 0%Not Expected”- 0%– ““Possible”- 25%Possible”- 25%– ““Probable”- 75%Probable”- 75%– ““Expected”- 100%Expected”- 100%

Optimal POSI and Deviation From Optimal POSI and Deviation From Optimal POSIOptimal POSI

Deviation from Optimal POSIDeviation from Optimal POSI (DO-POSI) refers to the (DO-POSI) refers to the difference between the category’s O-POSI and its difference between the category’s O-POSI and its

corresponding POSI.corresponding POSI.

DO-POSI = (O-POSI) – (POSI)DO-POSI = (O-POSI) – (POSI)– Positive(+); Over-forecastedPositive(+); Over-forecasted– Negative(-); Under-forecastedNegative(-); Under-forecasted

DO-POSI RESULTSDO-POSI RESULTS

CategoryCategory POSI(%)POSI(%) O-POSI(%)O-POSI(%) DO-POSIDO-POSI

Not ExpectedNot Expected 1.51.5 00 -1.5-1.5

PossiblePossible 34.534.5 2525 -9.5-9.5

ProbableProbable 85.785.7 7575 -10.7-10.7

ExpectedExpected 9595 100100 55

SummarySummary

New York CWSU SWAP forecasts achieve New York CWSU SWAP forecasts achieve goals for “Possible”, “Probable” and goals for “Possible”, “Probable” and “Expected” events.“Expected” events.

SWAP prediction is close to “optimal”.SWAP prediction is close to “optimal”. SWAP forecasts give air traffic managers, SWAP forecasts give air traffic managers,

airlines and other key customers quality airlines and other key customers quality decision-support information to support air decision-support information to support air travel.travel.