university of wisconsin convective initiation (uwci) developed by justin sieglaff, lee cronce, wayne...

University of Wisconsin Convective Initiation (UWCI)

Developed byJustin Sieglaff, Lee Cronce, Wayne Feltz

CIMSS UW-MADISON, MADISON, WI

Kris BedkaSSAI, HAMPTON VA

Mike Pavolonis and Andy HeidingerNOAA/STAR/ASPT MADISON, WI

What does satellite data add to convective detection?

UWCI Objectives• Provide a CI nowcast signal during day and night• Minimize false alarm at the expense of some

probability of detection• Use alternative method for time trend

computation (non-AMV) to minimize pixelation• Provide coherent radar-like satellite-based CI

signal as direct AWIPS/N-AWIPS satellite convective initiation decision support aid in field

Source of Confusion: More than one CI algorithm exists!

• CI from CIMSS– 24-hour coverage– Uses cloud-typing

algorithm to detect phase changes

– Uses multispectral GOES IR data

– Not computational intensive

– Being extended via object tracking

• CI from UAH (SatCast Ver2)– Daytime Only

(improved)– Uses pixel-based

mesoscale Atmospheric Motion Vectors

– Uses multispectral GOES IR data

– Being extended via object tracking

What is output from UWCI?• Value of 0: No CI nowcast• Value of 1: “Pre-CI Cloud Growth”: growing

liquid water cloud• Value of 2: “CI Likely”: associated with

growing supercooled water or mixed phase cloud

• Value of 3: “CI Occurring”: Associated with a cloud that has recently transitioned to thick ice – that is, it has glaciated





GROWING MEANS THE CLOUD IS COOLING, BECOMING TALLER





GROWING MEANS THE CLOUD IS COOLING, BECOMING TALLER

Once the cloud has glaciated, UWCI not needed

Characteristics of UWCI• Nowcasts cloud development in regions not

dominated by cirrus• Uses only IR channels from GOES satellite• Results available ~2 minutes after satellite scan

(distribution to AWIPS takes an additional 5-10 minutes)

• Operates in regular and RSO mode• Large spatial coverage: CONUS/Hawaii/Pacific• Up to 30-45 minutes of lead time before

significant radar echoes/lightning strikes• Low FAR, good POD, error sources understood

When should you use UWCI with caution?

• Algorithm does not work well where cirrus cloud cover exists

• Fast-moving clouds can cause false alarms• Thirty minutes between images? False alarm

rate increases• CI is more a diagnostic tool – that is, you lose

the good lead times – in true maritime Tropical airmasses

• Explosive development? UWCI may be more diagnostic

When should you use UWCI with caution?

• Algorithm does not work well where cirrus cloud cover exists

• Fast-moving clouds can cause false alarms• Thirty minutes between images? False alarm

rate increases• CI is more a diagnostic tool – that is, you lose

the good lead times – in true maritime Tropical airmasses

• Explosive development? UWCI may be more diagnostic (a function of time resolution)

UWCI: Algorithm logic – an overview in words

1. Box average 11 micron brightness temperature (BT) is calculated for current time and previous time, using specific classes from GOES Cloud Typing product

2. Unfiltered Cloud Top Cooling (CTC) Rate is calculated by differencing box average 11 micron BT for current time from previous time

3. Large/small box approach eliminates most of false CTC due to cloud motion (and additional checks reduce false cooling further)

4. CI Nowcast is assigned to remaining CTC pixels with cooling rates less than or equal to -4.0K/15 minutes by leveraging GOES Cloud Typing product

What is Box-Averaging?• Newly developing convective clouds move short distances

between successive images due to the high-temporal resolution of current GOES

• Clouds remain within a “boxed” region for 2 consecutive GOES scans. Mean IR temperatures and cloud microphysical properties of the clouds (i.e. “box-averaging”) can be differenced to identify new convective initiation

• This Eulerian framework means cloud motion is a significant issue: “new” non-convective clouds can enter the boxed region and influence the box-averaged properties, producing false cloud top cooling signal

• A set of tests is developed to preserve the signal associated with convective initiation while filtering out signal from rapidly moving and/or non-convective clouds

13 pixels

13 pixels

What is the box-averageTBB of the cloudy pixels(T1) in the small boxat the current time?

7 pixels

7 pi

xels

For the center (Yellow) pixel:

This is done for every pixel in the image; TBB is the 11-m brightness temperature

At each pixel alongthe perimeter:box-average the cloudy pixels in a7x7 box; find theminimum TBB for allpoints along theperimeter (T2)

13 pixels

13 pixels

What is the box-averageTBB of the cloudy pixels(T1) in the small boxat the current time?

7 pixels

7 pi

xels

If (T1-T2) < 0 K, then convectivecooling is occurring ;More than 1 pixel must be cloudyin the 7x7 box

For the center (Yellow) pixel:

This is done for every pixel in the image

At each pixel alongthe perimeter:box-average the cloudy pixels in a7x7 box; find theminimum TBB for allpoints along theperimeter (T2)

Which of these cooling points reflectscloud growth (in the vertical) and which reflects cloud motion (in the horizontal)?

Which of these cooling points reflectscloud growth (in the vertical) and which reflects cloud motion (in the horizontal)?

Also: Convective Initiation should ignore cooling cirrus clouds (where the initiationhappened a while ago!)

Look at the phase change, as well

All liquid & warmer than 32 F

Supercooled or mixedGlaciation has occurred

Convection develops whereCI predicted it along warm front

Cloud Mask finds cloudy pixels

Cloud typing determines the type of cloud

Surface Emissivity Surface Temperature

Clear-Sky Atmospheric Absorption/Emission information

10.7 m data

13.0 m data

3.9 m data

6.7 m data



Clear

Fog

Supercooled WaterWater

Mixed Phase

Cirrus

Thick Ice

Unknown

Cirrus overlap



Clear

Fog


Mixed Phase

Cirrus

Thick Ice

Unknown

Cirrus overlap

CI not computedfor these pixels




Mixed Phase

Cirrus

Thick Ice

Cirrus overlap




Mixed Phase

Cirrus

Thick Ice

Cirrus overlap

Determine percentages of each cloud type in 7x7 and 13x13 box

Determine cooling rate of cloudy pixels (normalized to a 15-minute t)

Throw out pixels that show warming relative to the valuesaround the perimeter of the larger box

Throw out pixels if >50% of pixels in large box are ice clouds

UWCI tests to reduce FAR• Throw out pixels that show warming relative to the values around

the perimeter of the larger box• Throw out pixels if >50% of pixels in large box are ice clouds• Throw out pixels if the number of cirrus/overlap pixels exceeds

the number of water cloud pixels• Throw out pixels if the number of overlap pixels exceeds the

number of water/supercooled/mixed phase pixels. Cloud-top cooling might mean thin cirrus are simply becoming thicker.

• Throw out pixels if the number of cirrus/overlap pixels exceed water/supercooled/mixed phase pixels at the earlier time and the number of water/supercooled/mixed phase pixels exceeds the number of cirrus/overlap pixels at the later time. CI means the relative number of ice compared to water pixels should be increasing.

IS THERE COOLING DUE TO CLOUD MOTION?

IS THE COOLING OUTSIDE THE MAIN UPDRAFT?

ARE THERETOO MANY ICE PIXELS?

IS THERE MOSTLY THIN CIRRUS WHEN MANY CLOUD TYPES ARE PRESENT?

ARE THEMICRO-PHYSICAL CHANGES‘WRONG’ ?

ARE THERE TOO MANY ‘OVERLAP’ PIXELS – CIRRUS PIXELS OVER LOW CLOUDS?

IS THEINFERRED THUNDER-STORM UPDRAFT IS TOO WEAK?

Examples!

20090429 Dryline CI Case20090429 Dryline CI Case

20090429 2015 UTCInstantaneous CI Nowcast

CI PossiblePossible

CI OccurringCI Occurring

CI LikelyCI Likely

20090429 2015 UTCInstantaneous CI Nowcast

CI Possible (All Possible (All ‘‘warmwarm’’ liquid) liquid)

CI Occurring (Glaciation)CI Occurring (Glaciation)

CI Likely (Supercooled/Mixed Phase)CI Likely (Supercooled/Mixed Phase)

(N-AWIPS Screengrab)

KAMA 2103 UTC Base Reflectivity


CI nowcast at 2015 UTC CI likely

CI occurring

Non-detection due to cirrus


First echo >= 35 dBZ, 17 minutes after nowcast

29 April 2009

SD/NE BorderWarm Frontal 0545 UTC 0546 UTC

0615 UTC0606 UTC

20090506 0545 UTC Nocturnal Instantaneous CI Nowcast

Nebraska 090724: Nocturnal Case

IR4 image and CTC at 0245Z

Radar reflectivity at 0246Z

IR4 image and CTC at 0315Z

Radar reflectivity at 0311Z

5151

AWIPS CI/CTC Interaction with Sullivan AWIPS CI/CTC Interaction with Sullivan (MKE) NWS Office(MKE) NWS Office

04:30 UTC

06:30 UTC

05:02 UTC

Forecaster generated screen captures from AWIPS at MKE

CI likely CI occurring

Lightning

4:31 Z

5:01 Z

6:31 Z

Where will development occur?

Cloud top cooling example in AWIPS

Satellite-based Convective Initiation Decision Support following to Milwaukee Weather Forecast Office, Storm Prediction Center, Aviation Weather Center, and Central Region NWS

Convective Initiation and Overshooting-top demonstration at NOAA HWT 2010

The following list of products offers opportunity for near-real time Warning Related utility. Now Available – Orange, Near Future - Green Baseline Products:Volcanic Ash: detection & Height - Alaska, Pacific, and AWC

Option 2 Products:Aircraft Icing Threat – NASA LaRC, Bill Smith JrTurbulence - AWCConvective Initiation (UWCI used where SATCAST not automated yet)Enhanced “V” / Overshooting Top Detection – HWT and HPCLow Cloud and Fog – AWC and AlaskaSO2 Detection – AWC and Alaska

70

University of Wisconsin Convective Initiation Proxy

Overshooting TopUWCI Cloud Top Cooling Rate

8-km Psuedo-GLM

24 May 2008

Accomplishments and Activities for Successful Research

More information on UWCI• Satellite blog:

http://cimss.ssec.wisc.edu/goes/blog (check on the ‘Convective initiation’ category)

• Strengths and weaknesses are discussed at http://cimss.ssec.wisc.edu/goes_r/proving-ground/GOES_CINowcast.htm

– Ice clouds and rapidly moving clouds cause problems

– 30-minute step between imagery? Detection drops

http://cimss.ssec.wisc.edu/goes/blog

http://cimss.ssec.wisc.edu/goes_r/proving-ground/GOES_CINowcast.htm

http://cimss.ssec.wisc.edu/goes_r/proving-ground/GOES_CINowcast.htm

Updates Since 2010 HWT• WMS serve of UWCI/OTTC

– http://wms.ssec.wisc.edu/gmaps/?products=conusvis.50,ci,wxwarn.35,nexrphase

• New Ice mask added to help forecasters determine where UWCI will not work (no cloud phase transitions)

• Added GOES-West and Hawaii domain– http://cimss.ssec.wisc.edu/snaap/convinit/quicklooks/

• Linking GOES convective cloud top cooling rate to anticipated future radar signal

• Use WDSS-II software to trackthe evolving 11 μm top of troposphere emissivity cloud field from cumulus infancy (3 sat. pixel minimum) to convective maturity (700 pixels).

• Simultaneously carry along UWCIcloud top cooling rate and CInowcasts, as well as various uniqueradar fields (i.e. Base; composite;and reflectivity at 0C, -10C, and -20C isotherms; VIL; MESH; POSH; etc.) for each unique object ID.

• State of the art framework for automated UWCI validation and computation of any lead-time value provided by UWCI CTC/CI prior to the above observed radar signatures for a given object.

"If the UWCI CTC algorithm has a developing convective cloud with a cooling rate of -15 K / 15 min, how often will that

developing storm achieve a VIL of 40 g/m2 ?

.. and just as importantly, with what lead time?"

GOAL: To provide additional support and warning leadtime for forecasters by addressing the following type of question:

• Various radar fields and thresholds to be studied are those most frequently observed with deep convection producing severe hail, wind gusts and tornadoes.

CI Conclusions

• Algorithm considers both cloud-top temperature changes and cloud type changes

• Works day and night• Lead time of up 45 minutes before 35 dbZ

echoes is common• Several checks to minimize false alarms:

When CI says convection is initiating, it usually is (POD: 55.6%; FAR: 26.0%)

CI Conclusions


• Works day and night• Lead time of 30 minutes before 35 dbZ echoes

is common• Several checks to minimize false alarms:


Nowcast forecasts more than half the storms that develop

Forecaster can trust that 3out of 4 forecasts verifies

CI Conclusions


• Works day and night• Lead time of 30 minutes before 35 dbZ echoes

is common• Several checks to minimize false alarms:


Nowcast forecasts more than half the storms that develop

Forecaster can trust that 3out of 4 forecasts verifies

Stats are from UWCI nowcasts and newly-developing CG-producing storms occurring within SLGT (or greater) RSK boxes for 23 convective afternoons (1800 – 0000 UTC) in Spring/Summer2008 and 2009. CI nowcasts: 288; LI events: 260. Includes clear sky days when POD is very highand cirrus-filled days when POD is low.

http://cimss.ssec.wisc.edu/snaap/convinit/quicklooks/

university of wisconsin convective initiation (uwci) developed by justin sieglaff, lee cronce, wayne...

Documents

ci algorithm

ci likely

ci nowcastvalue

preci cloud growth

satellitebased ci signal

liquid water cloudvalue

growing supercooled

uwci objectivesprovide