1. VISITview Teletraining Nearcasting Convection using GOES Sounder Data 1 ROBERT M. AUNE AND RALPH PETERSEN NOAA/ASPB/STAR JORDAN GERTH AND SCOTT LINDSTROM SSEC / CIMSS

2. VISITview Teletraining 2 Requirement, Science, and Benefit Requirement/Objective Mission Goal: Weather and water –Increase lead time and accuracy for weather and water warnings and forecasts –Improve predictability of the onset, duration, and impact of hazardous and severe weather and water events –Increase development, application, and transition of advanced science and technology to operations and services Science Can observations from a geostationary IR sounder be used to predict severe weather outbreaks 1 to 6 hours in advance, filling the gap between radar nowcasts and NWP models? Benefits Reduce loss of life, injury and damage to the economy Better, quicker, and more valuable weather and water information to support improved decisions Increased customer satisfaction with weather and water information and services

3. VISITview Teletraining Nearcasting uses GOES Sounder Data The GOES Sounder includes three separate water vapor channels The water vapor channels have weighting functions that peak in different parts of the troposphere (longer wavelengths see farther down into the atmosphere) Therefore have a three-dimensional look at atmospheric moisture 3

4. VISITview Teletraining 4 Note how sounder yields data at three levels! http://cimss.ssec.wisc.edu/goes/wf/faq.html

5. VISITview Teletraining 5 Note that the peak in the weighting function descends as the sounding dries out – you are looking at the radiation emitted by water vapor. As the sounding dries, less water vapor aloft to emit, so the sensor ‘sees’ farther down into the atmosphere (compare this page with the previous page)

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9. 9 Imager Water Vapor for weighting function slides

10. VISITview Teletraining 10 Imager Water Vapor for weighting function slides

11. VISITview Teletraining 11 Imager Water Vapor for weighting function slides Note Brightness Temperature values at CHS and LBF

12. VISITview Teletraining 12 Imager Water Vapor for weighting function slides Note Brightness Temperature values at CHS and LBF

13. VISITview Teletraining Nearcasting uses GOES Sounder Data Retrievals transform observed Sounder radiances to more common meteorological variables (e.g. temperature, dewpoint) that can then be used to compute other variables (e.g. Lifted Index, CAPE) Retrievals require clear skies Is there a way to ‘move’ the clear pixels now to future positions that may be cloudy? 13

14. VISITview Teletraining 14 Nearcasting Severe Convection Using the GOES Sounder GOES sounder provides hourly snapshots of layer- averaged stability parameters (for example,  e ). These observations can be assimilated at multiple levels into a Lagrangian model to provide fast, short- term projections of atmospheric stability. Lagrangian model uses model winds (u,v) and geopotential heights to guide motion of observations. Model output and sounder retrievals are blended together to yield t = 0 observations – thus, there is more horizontal coverage at t = 0 than just from sounder retrievals alone (cloudy regions and eclipse regions can be included)

15. VISITview Teletraining 15 Premise: Sounder gives information on distinct layers in atmosphere at observation time Winds from a numerical model can move those slabs of moisture around Question: Where does Convective Instability develop because of the moving slabs? Very Moist Layer Somewhat Moist Layer Very Dry Layer

16. VISITview Teletraining 16 Observations at this time are limited over the East Coast by plenty of cloudiness

17. VISITview Teletraining 17 00-h fields include information from previous runs; areal extent of information on East Coast is greater.

18. VISITview Teletraining 18 Cloud-free observations inside black curve – other obs are from earlier runs

19. VISITview Teletraining 19 Observations shown again

20. VISITview Teletraining How is nearcasting done? 20 12345 Data 6 6 56 456 3456 23456 etc. Data include winds and sounder observations of  e and  e that has moved to a point at time=0 and geopotential heights at t=0, 3 and 6h obs time increasing fcst time increasing 12345 134 3 2 1 1 21 2 Start at an initial time. Use a Lagrangian model. Step forward 6 hours. Output hourly forecasts Use hourly output as input into later forecasts etc.

21. VISITview Teletraining Benefit 21 As clouds develop in the daytime heated boundary layer, you still can track information from earlier observations. Retrievals aren’t made when clouds appear, but earlier information is still present in the advected fields There will be more coverage in the 00-h image than a sounder dataset for that same time because the 00-h fields include output from (up to) the previous 6 runs.

22. VISITview Teletraining Example: Yazoo City, MS tornado from 24 April 2010 Supercell developed in a region of extensive cloudiness, making Sounder data sparse However, available data and nearcast model output did suggest a region of strong convective instability in the region of tornadogenesis 22

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26. VISITview Teletraining 26 Tornado on ground in northeast Louisiana

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28. VISITview Teletraining 28 Tornados on ground in northeast Mississippi

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34. VISITview Teletraining 34 Sounder data ignored in the presence of clouds, but information still there in the holes in the cloud deck and in regions where data has moved from earlier times

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36. VISITview Teletraining 36 Minimum in stability indicated

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38. VISITview Teletraining 38 Convective Instability indicated (Tornado location and eventual track shown)

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44. VISITview Teletraining 44 Forecasts for 1800 UTC show excellent run-to-run continuity (See next six slides!)

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57. VISITview Teletraining Next Case: 2009 Case over NW Iowa Convection aligned in an arc similar in structure to that suggested by region of instability in nearcast output 57

58. VISITview Teletraining 58 How does this area of instability evolve?

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73. VISITview Teletraining Nearcasting uses GOES Sounder Data Lagrangian moisture transport controlled by RUC winds/height fields and GOES-East Sounder moisture. Moisture information is from three different levels in the atmosphere for Sounder, and for ABI (vs. 1 for Imager) Information can be moved into regions not covered by sounder because of clouds, eclipse, KOZ, etc. –Thus, you have information where you need it! 73 Conclusions

74. VISITview Teletraining Hail case from Wisconsin, 2006 Presented as a difference in Precipitable water between the two layers 6-h forecast shows strong increase in drying aloft in region where severe weather was reported Very large hail in Madison -- >2” in diameter 74

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82. VISITview Teletraining How do individual points move in the Lagrangian model? Note regions of convergence – points are coming closer together – and regions of divergence – points are moving farther apart with time. Lagrangian model is interpolated to a grid for hourly output Only one level is shown. Differing rates of convergence and divergence at different levels. For product to be computed, must have data at both levels 82

83. VISITview Teletraining How do individual points move in the Lagrangian model? In regions of divergence, number points in Lagrangian model output should decrease. Subsequent interpolation from Lagrangian Model to Grid used for output: Requires at least 2 Lagrangian points near the Grid to be considered ‘valid’ 83

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91. VISITview Teletraining What are error sources? Winds in the Lagrangian model are from the RUC. The level chosen to move moisture around must be correct 91

92. VISITview Teletraining 92 In this 6-h forecast, note that the axis of instability is near TUL

93. VISITview Teletraining 93 However, the axis of observed convection at that time is still back in central Oklahoma

94. VISITview Teletraining 94 Forecasts for 2200 UTC do converge to a solution showing max instability where observed.

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