Case Study:

Ivan - September 2004

Jared Klein – SUNY-Albany

300 hPa Analyses: 1200 UTC 16 September 2004

300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)

1.0° GFS

Precipitable water (mm), 300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)

300 hPa Analyses: 1200 UTC 17 September 2004

Precipitable water (mm), 300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)

300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)

1.0° GFS

Frontogenesis in jet-entrance region

Confluent flow in equatorward jet-entrance region

300 hPa Analyses: 1200 UTC 18 September 2004

Strengthening downstream ULJ and ridge

300 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)

1.0° GFS

Strong frontogenesis in jet-entrance region

Precipitable water (mm), 300 hPa h (dam), wind speed (m s−1), and div (10−5 s−1)

925 hPa Analyses: 1200 UTC 16 September 2004

925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)

WSI radar, 925 hPa θe (K) and wind barbs (kt)

Pre-existing baroclinic zoneSymmetric reflectivity structure

1.0° GFS

925 hPa Analyses: 1200 UTC 17 September 2004

925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)

WSI radar, 925 hPa θe (K) and wind barbs (kt)

Northeastward extension of precip field along baroclinic zone

1.0° GFS

Band of frontogenesis along baroclinic zone

925 hPa Analyses: 1200 UTC 18 September 2004

925 hPa frontogenesis [K (100 km)−1 (3 h)−1], θ (K), and wind barbs (kt)

WSI radar, 925 hPa θe (K) and wind barbs (kt)

Highest reflectivity near nose of LLJ/θe ridge axis

1.0° GFS

Strong frontogenesis along warm frontal zone

925 hPa Q Vector Diagnosis: 0000 UTC 18 September 2004

Radar at 1200 UTC 17 September 2004

Q Qn

QsRadar at 0000 UTC 18 September 2004

Highest reflectivity near strongest QG forcing for ascent

Radar at 0000 UTC 18 September 2004

WSI radar

Qs div–con couplet within thermal trough–ridge

Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors

Qn div–con bands within frontal zone

1.0° GFS

Radar at 1200 UTC 17 September 2004

Q Qn

QsRadar at 0000 UTC 18 September 2004

Highest reflectivity near strongest QG forcing for ascent

Radar at 0600 UTC 18 September 2004

WSI radar

925 hPa Q Vector Diagnosis: 0600 UTC 18 September 2004

Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors

1.0° GFS

Radar at 1200 UTC 17 September 2004Radar at 0000 UTC 18 September 2004Radar at 1200 UTC 18 September 2004

Q Qn

Qs

WSI radar

925 hPa Q Vector Diagnosis: 1200 UTC 18 September 2004

Q vectors (10−10 K m−1 s−1 beginning at 2.5 × 10−11), θ (K) contoured in green, and Q div–con (10−15 K m−2 s−1) shaded in cool–warm colors

1.0° GFS

Highest reflectivity near strongest QG forcing for ascent

Cross Section of Fn Magnitude: 0000 UTC 18 September 2004

Deep frontogenesis tilting toward cold air w/height

925–500 hPa layer-avg Fn vectors (10−10 K m−1 s−1),θ (K) contoured in green, and Fn div–con (10−15 K m−2 s−1) shaded in cool–warm colors

Fn magnitude [K (100 km)−1 (3 h)−1] shaded in green–blue, RH shaded in orange, θ (K) contoured in gray, wind barbs (m s−1), and ω<0 (µb s−1) contoured in red1.0°

GFS

Cross Section of Fn Magnitude: 1200 UTC 18 September 2004

Deep frontogenesis tilting toward cold air w/height

925–500 hPa layer-avg Fn vectors (10−10 K m−1 s−1),θ (K) contoured in green, and Fn div–con (10−15 K m−2 s−1) shaded in cool–warm colors

1.0° GFS

Fn magnitude [K (100 km)−1 (3 h)−1] shaded in green–blue, RH shaded in orange, θ (K) contoured in gray, wind barbs (m s−1), and ω<0 (µb s−1) contoured in red

Heaviest 6-h precip along and on cold side of surface boundary

6-h precipitation (in) ending at 0600 UTC 18 September 2004

0000 UTC 18 September 2004

NPVU QPE

Flow of tropical air into surface boundary

Fn vectors (10−10 K m−1 s−1 beginning at 1.0 × 10−10), θ (K) contoured in green, streamlines contoured in black, and Fn div–con (10−14 K m−2 s−1) shaded in cool–warm colors

~0.6° surface data

0600 UTC 18 September 2004

Heaviest 6-h precip along and on cold side of surface boundary

6-h precipitation (in) ending at 1200 UTC 18 September 2004

0600 UTC 18 September 2004

NPVU QPE

Flow of tropical air into surface boundary

Fn vectors (10−10 K m−1 s−1 beginning at 1.0 × 10−10), θ (K) contoured in green, streamlines contoured in black, and Fn div–con (10−14 K m−2 s−1) shaded in cool–warm colors

~0.6° surface data

1200 UTC 18 September 2004