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Yasi vs. Larry: What the Satellite Saw John Knaff NOAA/NESDIS –RAMMB Fort Collins, Colorado.

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Presentation on theme: "Yasi vs. Larry: What the Satellite Saw John Knaff NOAA/NESDIS –RAMMB Fort Collins, Colorado."— Presentation transcript:

1 Yasi vs. Larry: What the Satellite Saw John Knaff NOAA/NESDIS –RAMMB Fort Collins, Colorado

2 Overview TC Larry (2006) Landfall 20 March –South of Innisfail –95km S. of Cairns –940 hPa (best track, BoM) –959 hPa (measured, 2 -4 h post landfall) –100kt (10-min, BoM) –240 km/h gusts, BoM –115 kt (1-min, JTWC, best) –90 n.mi Gale force wind –30 n.mi Hurricane force wind –4.9 meter inundation –Average length track TC Yasi (2011) Landfall 3 February –near Mission Beach –138km S. of Cairns –929 hPa (Tully Sugar Mill) –110 kt (10-min, BoM) –135 kt (1-min, JTWC) –200 + n.mi Gale force winds –60 + n.mi Hurricane force winds –5 meter tidal surge –Fast translation –Long track

3 Larry Intensity (objective & subjective)

4 Digital Dvorak

5 Larry Landfall Intensity Best track BoM 100kt / 115 kt 940 hPa (table),959 hPa observed Gusts to 240 km/h damage derived JTWC 100 kt / 115 kt Translation 270/13 kt Imagery Subjective T-numbers of 6.5 (127 kt) are possible. 6-hour average close to 6.0

6 Eyewall Replacement? Microwave imagery (NRLMRY) IR imagery suggests Possible eyewall replacement starting at ~ UTC Microwave suggest two eyewalls a little earlier at 1541 UTC

7 Eyewall Replacement? 89 GHz 1700 UTC Radar Composite at 14 UTC

8 Landfall Larry appears to have experienced a quick eyewall replacement just prior to landfall –Double eyes evident in MI from 16 UTC on –Both radar and microwave imagery suggest a larger eye at landfall… replacement complete.

9 Larry was a small storm Operational Wind Radii12-h average IR image Area ~ 2560 km x 1920 km

10 reanalysis of Satellite-based Sfc Winds

11 Pressure-Wind ~ hPa nmi R34 13 kt translation 18S latitude Yields a 100/115 kt intensity.

12 Yasi Intensity

13 Digital Dvorak

14 Yasi Landfall Intensity Best track BoM 110 kt / 125 kt 929 hPa, observed …Gusts 280 km/h JTWC 120kt / 135 kt Translation 250/17 kt Imagery Subjective T-numbers of 7.0 (140) are possible, but not at the times of the fixes 6-h average close to 6.6

15 Landfall Yasi experienced only slight structural changes as it approached the coast –Unanticipated left turn delayed landfall –Large storm, stable eye size

16 Larry was a small storm Operational Wind Radii12-h average IR image Area ~ 2560 km x 1920 km

17 Real-time analysis of Satellite-based Sfc Winds

18 Pressure-Wind ~930 hPa nmi R34 17 kt translation 18S latitude Yields a 115/130 kt intensity.

19 Summary what the satellite saw Larry Small storm –Average R34 90 to 110 nmi –Short lifetime Major hurricane at landfall –Subjective Tnums of max=6.5 (127kt), mean=6.0 (115 kt) –Digital Dvorak T=7.5 (155 kt) –ODT N/A Eyewall cycle completing at landfall Factors (increase dvorak) –Translation at 13 kt (+) –Latitude =18S (-) –12-h trend up (+) –small (+) Yasi Larger storm –Average R to 230 nmi –Started large and had a long track. Major Hurricane at landfall –Subjective Tnums of max=7.0 (140 kt), mean=6.6 (130 kt) –Digital Dvorak T = 7.5 (155 kt) –ODT T= –Structure stable at landfall –Factors (increase Dvorak) Translation 17 kt (+) Latitude = 18S (-) 12-h trend slightly up (+) Large/average (-)

20 Conclusion at Landfall Larry Intensity should be close to 100/115 kt based on pressure, translation, latitude, size and damage –Dvorak estimates too high, especially Digital –AMSU estimates too low Satellite based size estimates seem able to conclude Larry was small Eyewall cycle completed around time of landfall Yasi Intensity should be close to 115/130 kt based on pressure, translation, latitude, size and damage –Dvorak estimates too high, particularly Digital, ADT –AMSU estimates too low, but better Satellite based size estimates seem able to conclude Yasi was average/large Showed that Yasis structure was fairly stable as it rapidly made landfall.

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23 JTWCs Track/Intensity/Size


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