Nowcasting Thunderstorm Intensity from Satellite

1
Nowcasting Thunderstorm Intensity from Satellite

• Robert M Rabin
• NOAA/National Severe Storms Laboratory
• Norman, OK USA
• Cooperative Institute for Meteorological
  Satellite Studies
• University of Wisconsin
• Madison, WI USA

2
Outline

• Purpose
• The first pictures (1960's) TIROS
• - Basic cloud structure, Environmental conditions
  
• GEO arrives (1970's) ATS and GOES
• - Time rate of change, anvil expansion
• - More structure, Enhanced-V
• Multispectral (1990's) AVHRR and GOES
• - Plumes, near storm environment
• Outlook for the future

3
Purpose

• Review past discoveries in relation to radar.
• Explore prospects for operational severe storm
  detection.

4
The First Pictures

• TIROS-I
• 27 May 1960, 1719 LST
• from L. Whitney
• JAM 1963
• Severe Storm Clouds
• as seen from TIROS

5
From L. F. Whitney, 1963, JAM, figure 3
6

• Clouds are conspicuous and distinctive
• Medium size, not linear
• Highly reflective, combined anvils
• Sharp edges, scalloped structure
• Much larger than area of radar echoes and sferics
• Contiguous clear areas, useful in determining
  severity?

7
Relationships between size of cirrus shields and
severity R.J. Boucher 1967, JAM
TIROS IV-VII 17 cases 1962-1964
From Fig. 2
8
From Fig. 3, Boucher 1967, JAM
9

• Diameter of cirrus shield is an index of storm
  severity
• - Rarely severe lt 60 n mi
• - Usually severe gt 150 n mi
• Penetrative convection not always severe weather
• Contiguous clear areas not common
• Results based on a limited sample of cases

10
Satellite imagery and severe weather
warnings James F.W. Purdom, 1971

• Polar orbiting NOAA-1
• Squall lines characteristic appearance,
  narrowing to south
• Locations of jets polar and subtropical
• Shear with height thermal ridge and amount of
  veering

11

• ATS-3 Visible imagery (1971)
• 11-minute updates on demand
• Early detection of squall lines as compared to
  radar
• Isolation of areas under threat for severe
  weather
• - Often southern portion of convective clusters
• Growth of anvil
• - Pause in expansion linked time of tornado
  occurrence
• - McCann(1979) linked collapsing tops to
  downdraft
• and tornado formation

12
Convective Initiation
Some uses of high-resolution GOES imagery in the
mesoscale forecasting of convection and its
behavior James F.W. Purdom, 1976 MWR
13

• Detection of mesoscale processes
• - Important for storm initiation and maintenance
• - Effects of terrain (coast lines, rivers and
  lakes)
• Precise location of convective (outflow)
  boundaries
• Merging and intersecting of boundaries
• Given favorable conditions
• - New convection and intensification

14
Exploration of Infrared imagery
15
Detection of tropopause penetrations byintense
convection with GOES enhanced infrared
imageryPeter Mills, Elford Astling, 1977, 10th
SLS

• First observations of warm spots on anvil
• Near tropopause penetrations
• - confirmed by radar
• Possible causes
• - higher emissivity above updraft
• - stratospheric cirrus
• - rapid sinking

16
Anvil outflow patterns as indicators of tornadic
thunderstorms Charles E. Anderson, 1979

• Observed characteristics of cirrus plumes
• of severe storms (limited cases)
• - Displaced to the right of the ambient wind
• - Anticyclonic rotation
• - Spiral bands
• - Similarity to hurricanes

17
On overshooting-collapsing thunderstorm
topsDonald W. McCann, 1979

• Previously observed by aircraft (Fujita,
  73Umenhofer, 75)
• Collapse does NOT cause tornado
• May be related to acceleration of gust front
• - Occlusion of mesolow
• - Strong surface outflow (i.e. bow echo)

18
Thunderstorm intensity as determined from
satellite data (SMS 2 IR 5-minute)Robert Adler
and Douglas Fenn, JAM 1979
19

• Tornadoes during or after rapid expansion (7 of
  8)
• Statistical relation to severe weather
• - Severe storms colder and more rapid growth
• Potential warning lead time 30 minutes
• Divergence and vertical velocity
• - Twice as large for severe storms
• Limitations
• - Results from a single day
• - Existing anvil may obscure new storm growth
• - Storm top heights underestimated as compared
  to radar

20
Mesoscale convective complexesRobert Maddox,
1980 BAMS
21

• Identified unique class of convective system
• Defined from IR imagery
• - Cold cloud tops (lt -32 C)
• - Size (gt 100,000 km2)
• - Shape circular (eccentricity gt 0.7)
• - Duration gt 6 hours
• Produce wide variety of severe weather
• Difficult to forecast
• - Weak upper-level support
• - Low-level warm advection

22
Observations of damaging hailstorms from
geosynchronous satellite digital data (GOES
30-minute data 9 storms) David W. Reynolds,
1980 MWR
23

• Cloud tops colder than tropopause
• - Infer vigorous updrafts
• Expect better relation for hail
• - Tornadoes depend on boundary layer conditions
• Large hail storms
• - Long lasting (3-5 h)
• - Large, high cloud tops
• Onset of large hail
• - Rapid vertical growth
• - Cloud top becoming colder than tropopause
• Requires proper enhancement

24
The enhanced-V a satellite observable severe
storm signature Donald W. McCann 1983, MWR
25

• Relatively large sample 884
• Interaction of winds and overshooting tops
• - Strong upper level wind (20-60 m/s)
• Many severe storms do not have enhanced-V
• - POD is low ( .25 )
• - Cause of enhanced-V needs more research
• FAR similar to other methods (.31)
• Lead time of 30 minutes
• Requires proper enhancement

26
Detection of severe Midwest thunderstorms using
geosynchronous satellite data SMS-2 and GOES-1
5 minute data Robert Adler, Michael Markus,
Douglas Fenn MWR 1985
27

• Combine parameters into single index
• Index correlated with severe weather and max
  reflectivity
• - Parameters related to updraft intensity
• - Cloud top ascent rates
• - Expansion rates of isotherms
• - Based on 4 dependent, 1 independent case
• V-shape with embedded warm spot
• - Similar to McCann findings
• Limitations
• - Identification of cloud tops during certain
  stages
• - Resolution in IR (cloud tops too warm)
• - Ambiguity in height from cloud top temperature

28
Thunderstorm cloud top dynamics as inferred
from satellite observations and a cloud top
parcel model Robert Adler, Robert Mach, 1986 JAS
29

• Used GOES stereoscopic observations (May 1979)
• Three classes of storms identified and simulated
• - 1. concentric monotonic temperature-height
• Cold-warm couplet with coldest and highest point
• - 2. collocated isothermal
• - 3. offset inversion with mixing
• Close in warm point subsidence undershooting

30
Upper-level structure of Oklahoma tornadic
storms on 2 May 1979, I Radar and satellite
observations Gerald Heymsfield, Roy Blackmer,
Steven Schotz JAS, 1983
31

• Three severe storms investigated (single day)
• V pattern of low cloud top temperature
• - Strong divergence
• Close-in warm area
• - 10-20 km downwind
• - Moves with storm motion
• - Forms at time of tropopause penetration
• - Subsidence mechanism proposed
• Distant warm area (not in all cases)
• - 50-75 km downwind
• - Moves with upper-level winds
• - No visible stratospheric cirrus

32

• Rapid growth stage
• - Cold areas collocated with radar echo
• After rapid growth
• - Cold areas sometimes displaced from echo core
• IR temperature change
• - Not always consistant with stereographic
• height change

33
Satellite-observed characteristicsof Midwest
severe thunderstorm anvilsGerald Heymsfield, Roy
Blackmer, MWR 1988
34

• Statistics from several cases (9)
• Thermal couplets
• - Second distant warm point often observed
• - Width of V spacing of cold and distant warm
• - T-diff (warm-cold) related to amount of
  overshoot
• Ingredients for V
• - Strong shear near troposphere
• - Intense updrafts and overshooting tops

35

• Various hypotheses
• - Internal cloud dynamics
• - Radiative transfer effects
• - Flow over and around storm top waves
• - Combination of above
• Limitations
• - IR pixel resolution
• - Unknown temperature and ice crystal structure
• - Complexity of multistorm structure
• - 3-D models too simplified

36
Aircraft overflight measurements of
Midwestsevere storms Implications on
geosynchronous satellite interpretationsGerald
Heymsfield, Richard Fulton, James Spinhirne, MWR
1991
37

• Dimensions of overshooting tops
• - Size of single GOES pixel
• - 15 degs colder than GOES
• Thermal couplets much more pronounced
• Warm areas not due to variation in optical depth
• Above cloud wind and temperature perturbations
• - Cold dome in temperature field

38
The AVHRR channel 3 cloud topreflectivity of
convective stormsMartin Setvak, Charles
Doswell, 1991 MWR
39

• Areas of enhanced reflectivity at 3.7 microns
• - Convective cell widespread or localized
• - Plume-like less common
• Association with hail (limited sample)
• Not often associated with V
• Possible cause
• - Very small ice crystals
• - Generated from vigorous updrafts

40
Passive microwave structure of severe tornadic
storms on 16 November 1987Gerald Heymsfield,
Richard Fulton, 1994 MWR
41

• Maximum polarization difference at 86 Ghz
• - Correlates with internal warm region
• - Convective core
• Symmetrical or tumbling ice particles
• Small polarization difference
• - Warm region
• Oriented ice crystals
• Large polarization difference
• Microphysical variations
• - Partially explain IR structure

42
Multispectral high-resolution satellite
observations of plumes on top of convective
stormsVincenzo Levizzani, Martin Setvak, 1996
JAS
43

• Enhanced reflectivity
• - Small ice crystals
• - Limited growth time strong updraft (BWER)
• - Vertical lifting/gravitational settling
• Vertical separation between plume and anvil
• Different from Fujita's (1982) stratospheric
  cirrus
• Link between plume source position and warm spot

44
Satellite observations of convective storm tops
in the 1.6, 3.7 and 3.9 spectral bandsMartin
Setvak, Robert Rabin, Charles Doswell, Vincenzo
Levizzani, 2003 Atmos. Res.
45

• Study used GOES and Doppler radar
• Areas of high cloud top reflectivity
• - Time scales minutes to hours
• - Size pixels to entire anvils
• - Linked to mesocyclone formation
• - Move downwind once formed
• - Not always associated with mesocyclones
• Mechanisms remain unknown

46
Moisture plumes above thunderstorm anvils and
their contributions to cross-tropopause transport
of water vapor in midlatitudesPao Wang, 2003, JGR
47

• Storm simulated using 3-D, non-hydrostatic model
• Water vapor source shell of overshooting dome
• Gravity waves
• Waves break when instability becomes large
• Water vapor injected into stratosphere
• Carried downwind in shape of a chimney plume
• Transport of water vapor to stratosphere 3
  tons/sec

48
Nowcasting storm initiation and growthusing
GOES-8 and WSR-88D dataRita Roberts, Steven
Rutledge, 2003 WF
49

• Based on observed cloud growth rates
• - Eastern CO (4 days),
• - Washington DC and New Mexico (2 days)
• Onset of storm development
• - Surface convergence features
• gust fronts, rolls, terrain, intersecting
  features
• - Cloud tops reaching sub-freezing altitudes
• - Rapid cooling of cloud tops

50

• Intensity related to rate of cooling
• Increased lead time
• - 15 minutes prior to 10 dBZ echoes aloft
• - 30 minutes prior to 30 dBZ echoes aloft
• NCAR automated nowcasting system

51
NCAR auto-nowcast systemCindy Mueller et al,
2003, WF
52

• Provides short-term (0-1 hr) nowcasts of storm
  location
• Identify boundary layer convergence lines
• Fuzzy logic to combine predictor fields
• - Radar, satellite, mesonet, profilers, models
• Improves over extrapolation and persistence
• - Tested at 3 locations (3 years)
• - Plans to include in NWS AWIPS

53
Validation and use of GOES sounder
informationTim Schmit, et al., 2002 WF
54

• Thermodynamic stability parameters
• - CAPE, CIN, PW
• - Hourly updates for time trends
• - Horizontal resolution (10 km)
• - Only available in clear areas
• Subjective use in forecast offices
• Limited use in NWP

55
Storm trackerA Web-based tool for monitoring
MCSRobert Rabin, Tom Whittaker 2004
56

• Identify and track MCS
• - Cold cloud tops
• - Radar reflectivity
• - Adjustable thresholds
• Time trends of MCS characteristics
• - Size
• - Cloud top temperature stats
• - Radar reflectivity stats
• - Lightning
• - Storm environment from RUC,...
• Real-time and archived data on-line
• Data access from NOMADS/THREDDS catalog

57
Data Flow
Radar
Tracking Algorithm
Lightning
Web Server
GOES
THREDDS
RUC model analysis
58

• Example session

59
(No Transcript)
60
(No Transcript)
61
(No Transcript)
62
(No Transcript)
63
(No Transcript)
64
(No Transcript)
65
(No Transcript)
66
(No Transcript)
67
Summary

• 40 year history of satellite research
• Hot research topic through 1980's
• Limits to Operational use of early ideas
• - Advent of Doppler radar network
• - Resolution limitations
• - Limited early access
• Greatest impact qualitative use of imagery

68

• The Future?
• MSG (now)
• AWIPS
• GOES-R (2013)
• Space-borne Radars?