forecasting the propagation of thunderstorm anvil clouds...

NASA - USAF - NOAA Applied Meteorology Unit

Slide 1

FORECASTING THE PROPAGATION OF THUNDERSTORM ANVIL CLOUDS OVER FLORIDA

USING NCEP MODEL DATA

Mark M. WheelerDavid A. Short

ENSCO, Inc.Applied Meteorology Unit

NASA/KSC/CCAFS

NWA Annual Meeting22 October 2003

Jacksonville, Florida


Slide 2

OUTLINE

MotivationNatural & Triggered Lightning:

Threat to Space Launch & Landing

Empirical Study Florida Anvil Clouds

Lifetime & Propagation Characteristics

Nowcast Tool Used During Countdown

Wind Speed/Direction (300 to 150 mb)

Forecast Tool24 to 48 Hour Scrub Forecast

Eta-Model Forecast Winds


Slide 3

Anvil Cloud Rule

Rule 3a1

DON’T launch if the flight path will carry the vehicle throughnontransparent parts of attached anvil clouds

OK

Attached Anvil


Slide 4

STS-105 Post-Mission Summary Spaceflight Meteorology Group

Johnson Space Center (JSC/SMG)

Aug. 9, 2001 SCRUB Aug. 10, 2001 LAUNCH

“… Although no rain wasreported at KSC, thunderstormswere close enough to the Return-To-Launch-Site (RTLS)emergency landing approachesto halt the launch countdown.In addition, the anvil cloud fromthe thunderstorms had movedoverhead of both the SLF andthe launch pad violating boththe Flight Rules for emergencylandings and the Launch CommitCriteria.”


Slide 5

ANVIL FORECASTING CHALLENGEThe 45th Weather Squadron and the Spaceflight Meteorology Group identify anvil forecasting as one of their most challenging tasks when predicting natural and triggered lightning threats

IMPLEMENTATIONCombine lifetime and propagation statistics of thunderstorm anvil clouds over Florida withan operational, graphical forecast tool to assist forecasters in assessing the potential for lightning threats to

space launch and landing operations from thunderstorm anvil clouds


Slide 6

Anvil Layer:(Warm Season)

150 mb (46 000’)

300 mb (31 000’)

Anvil Transport by Upper-Level Winds

Anvil Transport Distance

ParentThunderstorm

Complex

Greatest Extent ofNon-Transparent Edge


Slide 7

AMU AnvilsDaily Averages

y = 1.9x + 21R2 = 0.73

0

25

50

75

100

125

150

0 25 50 75

Wind Speed (300-150 mb, kts)

Dist

ance

(nm

)

a

AMU Anvils - OffsetEffective Lifetimes

0

25

50

75

100

125

150

0 25 50 75


Dist

ance

- 21

(nm

)

1-hour

2-hours

3-hoursb

Analysis of 50 case days in May – July 2001(167 anvils)


Slide 8

http://www.auf.asn.au/meteorology/section3.html

Australian Anvil: Diameter ~ 20 n mi


Slide 9

Daily Anvil Orientation

0

60

120

180

240

300

360

0 60 120 180 240 300 360

Wind Direction (300-150 mb)

Anvi

l Orie

ntat

ion

Direction DifferenceAnvil - Wind

-90

-60

-30

0

30

60

90

0 20 40 60


Anvi

l Orie

n. -

Win

d Di

r.

Anvil Orientation and Wind Direction(300 to 150 mb Layer)


Slide 10

Parameters for an

Anvil Threat Sector:

20 n mi Stand-off Circle

30° Threat Sector Width

Orientation given by 300 to 150 mb Wind Direction

1-, 2- and 3-hour Arcs in Upwind Direction

Distances given by 300 to 150 mb Wind Speed


Slide 11

EXAMPLETSTM GUIDANCE:

ETA-MOS 12-HR PROBABILITY OF THUNDERSTORMS (LTNG): The probability that a thunderstorm will occur in a 40 km grid box during the 12 hour period ending at the specified time. A thunderstorm is defined as 1 or more cloud-to-ground lightning strikes.

Anvil Threat Sectors Observed

36-hr Forecast

McIDAS-type Display: Anvil Tool written in McBASI


Slide 12

SUMMARY:

Thunderstorm Anvil Threat Sector:Delineates potential area of concern

Nowcast Threat Sector: Based on observed 300 to 150 mb winds

Forecast Threat Sector:Based on Eta or MRF point data (winds)

[Other guidance needed for thunderstorm probability]

AMU Quarterly Reports:http://science.ksc.nasa.gov/amu/home.html


Slide 13

Blank


Slide 14

Ocean Anvil case from 45 WS Pilot Study


Slide 15

GOES-8; May 13, 2001

Prototype Threat Sector Tool (McBASI)

forecasting the propagation of thunderstorm anvil clouds...

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