Hurricane Juan (2003): A Diagnostic and Compositing Study

1
Hurricane Juan (2003)A Diagnostic and
Compositing Study

• Ron McTaggart-Cowan1, Eyad Atallah2, John
  Gyakum2, and Lance Bosart1

1 University of Albany, Albany NY 2 McGill
University, Montreal, QC
2
Outline

• Introduction and background
• Compositing study
• Analysis of Hurricane Juan's lifecycle
• Midlatitude precursors
• Easterly wave development
• Tropical transition
• Summary and discussion

2215 UTC 28 September 2003
QuikSCAT-NRT Image courtesy of NRL
3
Introduction and Background

• First identified as a TD at 12/24
• Maximum intensity of Cat 2 969 hPa (90 kt) at
  18/27
• Landfall near Halifax, NS at 03/29

NHC Best Track for Hurricane Juan (2003)
4
Introduction and Background

• Hurricanes usually recurve east of Nova Scotia
  under westerlies
• Extratropical transition is expected in the
  midlatitude flow

Photo courtesy of the Canadian Hurricane Centre
How common is Atlantic hurricane landfall at high
latitudes?
5
Compositing Study

• Composite search criteria
• Atlantic hurricanes between 1948 and 2002
• Landfall north of 40oN (NHC Best Track)
• Motion vector in the northern quadrant on landfall

Carol (1953) Ginny (1963) Carol (1954) Gerda
(1969) Edna (1954) Blanche (1975) Donna
(1960) Bertha (1990)
The NCEP Reanalysis (2.5o grid) dataset is used
for composite analysis
6
Compositing Study

• 500 hPa heights and anomalies prior to landfall
  (T-00h)
• Shading indicates statistical significance
• Propagating ridging builds along the east coast
  before landfall

time
7
Compositing Study

• Meridional flow over eastern North America with a
  trough/ridge couplet along the Eastern Seaboard
• Strong southerly geostrophic steering flow
• Warm through a deep layer ahead of the storm
• Low shear midlatitude environment

8
Lifecycle Analysis - Midlatitude Precursors
Dynamic tropopause (2 PVU surface) potential
temperature in colour. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
B
A
T
0000 UTC 24 September
9
Lifecycle Analysis - Midlatitude Precursors
Dynamic tropopause (2 PVU surface) potential
temperature in colour. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
B
A
T
0000 UTC 25 September
10
Lifecycle Analysis - Midlatitude Precursors
Dynamic tropopause (2 PVU surface) potential
temperature in colour. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
B
A
J
0000 UTC 26 September
11
Lifecycle Analysis - Midlatitude Precursors
Dynamic tropopause (2 PVU surface) potential
temperature in colour. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
B
J
A
0000 UTC 27 September
12
Lifecycle Analysis - Midlatitude Precursors
Dynamic tropopause (2 PVU surface) potential
temperature in colour. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
A
J
B
0000 UTC 28 September
13
Lifecycle Analysis - Midlatitude Precursors
Dynamic tropopause (2 PVU surface) potential
temperature in colour. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
A
J
B
0000 UTC 29 September
14
Lifecycle Analysis Easterly Wave

• Strong EW crosses West African coast on 00/11,
  focusing convection as it propagates
• By 00/20, the EW structure becomes complex as

it begins to interact with a digging upper-level
trough
850 hPa relative vorticity on subdomains showing
the propagation of Juan's easterly wave
precursor. Dates as indicated on the individual
panels.
15
Lifecycle Analysis Tropical Transition

• EW provides lower-level vorticity seed
• Upper-level PV tail provides a band of
  synoptically-forced ascent
• Although each structure in itself is insufficient
  to produce a self-sustaining system (i.e. WISHE
  Emanuel 1987) their combination is
• The tropical transition of Hurricane Juan follows
  the Weak Extratropical Cyclone (WEC) paradigm of
  Davis and Bosart (2004)

16
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
T
0000 UTC 24 September
17
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
T
1200 UTC 24 September
18
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
T
0000 UTC 25 September
19
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
T
1200 UTC 25 September
20
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
J
T
0000 UTC 26 September
21
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
T
J
1200 UTC 26 September
22
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
J
0000 UTC 27 September
23
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
S
J
1200 UTC 27 September
24
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
J
0000 UTC 28 September
25
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
J
1200 UTC 28 September
26
Lifecycle Analysis Tropical Transition
Loop 00/24 - 00/29
Dynamic tropopause (2 PVU surface) potential
temperature in colour. 850 hPa relative
vorticity is contoured at 6x10-5 s-1 intervals
above 1.2x10-4 s-1. Winds on the dynamic
tropopause are plotted in white/black for
readability only. Short, long and flag pennants
represent 5, 10 and 50 kt winds, respectively.
J
0000 UTC 29 September
27
Lifecycle Analysis Tropical Transition
Loop 00/24 - 12/26
Potential temperature anomaly on the dynamic
tropopause (2 PVU surface) relative to the Eady
basic state. Sea level pressure isobars are
contoured in black at 4 hPa intervals.
S
L
T
0000 UTC 24 September
28
Lifecycle Analysis Tropical Transition
Loop 00/24 - 12/26
Potential temperature anomaly on the dynamic
tropopause (2 PVU surface) relative to the Eady
basic state. Sea level pressure isobars are
contoured in black at 4 hPa intervals.
S
L
T
1200 UTC 24 September
29
Lifecycle Analysis Tropical Transition
Loop 00/24 - 12/26
Potential temperature anomaly on the dynamic
tropopause (2 PVU surface) relative to the Eady
basic state. Sea level pressure isobars are
contoured in black at 4 hPa intervals.
S
L
T
0000 UTC 25 September
30
Lifecycle Analysis Tropical Transition
Loop 00/24 - 12/26
Potential temperature anomaly on the dynamic
tropopause (2 PVU surface) relative to the Eady
basic state. Sea level pressure isobars are
contoured in black at 4 hPa intervals.
S
L
T
1200 UTC 25 September
31
Lifecycle Analysis Tropical Transition
Loop 00/24 - 12/26
Potential temperature anomaly on the dynamic
tropopause (2 PVU surface) relative to the Eady
basic state. Sea level pressure isobars are
contoured in black at 4 hPa intervals.
S
J
T
0000 UTC 26 September
32
Lifecycle Analysis Tropical Transition
Loop 00/24 - 12/26
Potential temperature anomaly on the dynamic
tropopause (2 PVU surface) relative to the Eady
basic state. Sea level pressure isobars are
contoured in black at 4 hPa intervals.
S
J
T
1200 UTC 26 September
33
Summary and Discussion

• Both the compositing and the case study shows
  that east coast ridging is important for high
  latitude landfalling hurricanes
• Enhances southerly geostrophic steering flow
• Creates a warm environment conducive the
  maintenance of the tropical vortex
• Reduces shear and decreases baroclinicity ahead
  of the hurricane
• Hurricane outflow reinforce the pre-existing ridge

34
Summary and Discussion

• Easterly wave and midlatitude trough (PV tail)
  features interact during Juan's tropical
  transition
• A Weak Extratropical Cyclone (Davis and Bosart
  2004) transition occurs
• Strong coupling of the lower-level perturbation
  to the upper-level disturbance during transition
• A convective mesoscale vorticity maximum is
  enhanced by synoptically-forced ascent