Art Douglas and Phil Englehart Creighton University

An Historical Analysis of An Historical Analysis of Transient Rain Bearing Transient Rain Bearing Systems in the NAME Systems in the NAME Domain:Domain:The Impact of Inverted The Impact of Inverted Troughs on Monsoon Rainfall Troughs on Monsoon Rainfall

Art Douglas and Phil EnglehartArt Douglas and Phil EnglehartCreighton Creighton UniversityUniversity

Research ObjectivesResearch Objectives 1. To develop an historical climatology of 1. To develop an historical climatology of

transient synoptic systems in northern Mexico.transient synoptic systems in northern Mexico.

2. To determine relationships between these 2. To determine relationships between these transient systems and fluctuations in summer transient systems and fluctuations in summer rainfall.rainfall.

3. To relate variability in the frequency of 3. To relate variability in the frequency of transient systems to large scale oceanic and transient systems to large scale oceanic and atmospheric anomalies.atmospheric anomalies.

4. To provide a benchmark for modeling 4. To provide a benchmark for modeling studies in order to determine model studies in order to determine model performance relative to the prediction of these performance relative to the prediction of these transient features and their associated rainfall.transient features and their associated rainfall.

Transient Synoptic Features Transient Synoptic Features Affecting Northern MexicoAffecting Northern Mexico

1. Tropical Cyclones (Published).1. Tropical Cyclones (Published). 2. Inverted Troughs: Cold and 2. Inverted Troughs: Cold and

Warm.Warm. 3. Cold Fronts.3. Cold Fronts. 4. Cutoff Lows.4. Cutoff Lows. 5. Open Troughs.5. Open Troughs.

2222

22222

2

333333

33 3

33

333

4

444 4

4

44

44

44 6

6

666

666

6

555

5

555

55

5

55 5

77

77

777

7777

11

11 111 11 1

1

Data availability: 1950-2001

LO N G -T ER M ST AT I O N S SEVEN SY N O P T I C R EGI O N S

D A I L Y R A I N F A L L C L I M A T O L O G Y ( 1 9 6 1 - 9 0 )( J u n e 1 - S e p te m b e r 3 0 )

C L A S S I C M O N S O O N

N O R T H E A S T & I N T E R I O R

DA

ILY A

VG

. R

AIN

FALL

(m

m)

DAIL

Y A

VG

. R

AIN

FALL

(m

m)

0

1

2

3

4

5

6

7

8

9

0

1

2

3

4

5

6

7

8

9

0123456789

10

0123456789

10

S I N A L O AS I N A L O A - S O N O R A

S O N O R AS O U T H E A S T A R I Z O N A

T A M A U L I P A SD U R A N G OC H I H U A H U A

J U J L A U S

J U J L A U S

T R O P IC A L C Y C L O N E TO T O T A L S E A S O N A LR A IN F A LL (M E D IA N P E R C E N TA G E )

310

763

222

60 6

64020

533

0 1 20 2

0 24 7

38

3 46

8 109

1010

14399 830

16 817

21126 7

83 4

58

24

38

T C R A I N F A L L ( m m ) v s . L A N I Ñ Ab y A M O P H A S E

4 1 4 8

3 5 5 1

1 1 2 1 0 85 5

5 9

1 2 4 4 6

1 4 5 1 0 1

1 3 4 1 6 81 1 5

1 5 6

2 0 1 1 4 4

2 4 7 3 4

P O S I T I V E A M O N E G A T I V E A M O

1 6 8 9 6

2 0 5 8 66 8

3 3

2 2 7 7 0

1 5 1 8

2 0 1 1 0 7

2 1 7 1 5 3

2 0 7 1 1 2

4 2 3 6

1 2 5 7 7

4 2 8 6

1 2 5 4 3 1 1 7

1 7 1

1 1 8 1 8 2

1 2 4 1 0 7

9 5 1 5 3

1 5 2 9 8

2 0 9 1 2 52 0

2 3

1 5 1 3

1 8 2 7

2 8 3 3

1 8 2 6

8 4 4 2

6 6 5 3

6 0 7 7

5 1 6 9

1 1 11 2 9. 4 1 7 5

9 1

Transient Synoptic Features Transient Synoptic Features Affecting Northern MexicoAffecting Northern Mexico

1. Tropical Cyclones (Published).1. Tropical Cyclones (Published). 2. Inverted Troughs: Cold and 2. Inverted Troughs: Cold and

Warm.Warm. 3. Cold Fronts.3. Cold Fronts. 4. Cutoff Lows.4. Cutoff Lows. 5. Open Troughs.5. Open Troughs.

RAOB Sites

NOAA NWS LIBRARYNOAA NWS LIBRARY

Meridional Wind Time Section8 July to 12 August 2005

Meridional Wind Time SectionJuly 1973

N u m b er o f I n verted T ro u g h - D ays o ve r th e N A M D o m a in 1 9 6 7 - 2 0 0 1

1965 1970 1975 1980 1985 1990 1995 2000 200508

162432404856647280

Day

s

1965 1970 1975 1980 1985 1990 1995 2000 200508

162432404856647280

Day

s

C o m p a r is o n o f N u m b e r o f S y n o p t ic F e a tu r e so v e r th e N A M D o m a in

C L I M O v s 2 0 0 4

F R O N T S I N V E R T E D T R O U G H S

C U T - O F F L O W S

O P E N T R O U G H S

10

20

30

40

50

60

No. of D

ays

3 . 52 . 1

4 . 43 . 5

6 . 33 . 9

6 . 24 . 2

5 . 23 . 0

3 . 51 . 7 5 . 2

2 . 4

167

125

161

148

173

208216

Average Daily Rainfall (mm)

Inverted Trough Daysvs.

Days with No Synoptic Feature

Increase in Daily Rainfall (%)

Inverted Trough Dayswith respect to

Days with No Synoptic Feature

51.922.3

72.315.7

121.020.5

137.921.7

116.225.6

93.127.4 101.1

19.9

Inverted Troughs Contribution to Seasonal (June-Sept) Rainfall (1967-2001)

Average Rainfall (mm) Percent Contribution to Seasonal Total

-4-3-2-11 2 3 40

1

2

3

4

5

6

7

8

9

-4-3-2-11 2 3 40

1

2

3

4

5

6

7

8

9

-4-3-2-11 2 3 40

1

2

3

4

5

6

7

8

9

RAINFALL Associated with INVERTED TROUGHS as a function of TROUGH POSITION (i.e. Displacement East (-) or West (+) of the Division Location in º Long.) SONORA/SINALOA DURANGO TAMAULIPAS/NUEVO LEON

16.722.3

25.615.7

11.820.5

16.521.7

20.625.6

23.627.4 8.9

19.9

CONTRIBUTION OF INVERTED TROUGHS TO SEASONAL TOTAL RAINFALL

2004/CLIMO

0 14 28 42 56 70 84 98 112 1260

2

4

6

8

10

12

14

16

18

Rai

nfal

l (m

m)

0 14 28 42 56 70 84 98 112 1260

2

4

6

8

10

12

14

16

18

Rai

nfal

l (m

m)

C L I M O

2 0 0 4

SONORA DAI LY R AI NFALL (mm) 2 0 0 4 vs C L I M O (11-pt Binomial Smoothing)

J U N E 1 = 1

Transient Synoptic Features Transient Synoptic Features Affecting Northern MexicoAffecting Northern Mexico

1. Tropical Cyclones (Published).1. Tropical Cyclones (Published). 2. Inverted Troughs: Cold and 2. Inverted Troughs: Cold and

Warm.Warm. 3. Cold Fronts.3. Cold Fronts. 4. Cutoff Lows.4. Cutoff Lows. 5. Open Troughs.5. Open Troughs.

N u m ber o f F ron ta l D ays o ver th e N A M D om ain 1 9 6 7 - 2 0 0 1

1965 1970 1975 1980 1985 1990 1995 2000 200506

121824303642485460

Day

s

VIS 16Z October 7, 2005VIS 16Z October 7, 2005

Total Rainfall October 2-7, 2005Total Rainfall October 2-7, 2005

C o m p a r is o n o f N u m b e r o f S y n o p t ic F e a tu r e so v e r th e N A M D o m a in

C L I M O v s 2 0 0 4

F R O N T S I N V E R T E D T R O U G H S

C U T - O F F L O W S

O P E N T R O U G H S

10

20

30

40

50

60

No. of D

ays

1965 1970 1975 1980 1985 1990 1995 2000 20050

10

20

30

40

50

% s

easo

n al t

otal

1965 1970 1975 1980 1985 1990 1995 2000 20050

10

20

30

40

50

% s

easo

n al t

otal

2 0 0 4 = 5 .6 C L IM O = 5 .9

TAMAULIPAS/NUEVO LEON (DIVISION 7)Percentage of Total Seasonal Rainfall Associated with Fronts (< 350 km)

C o m p a r is o n o f N u m b e r o f S y n o p t ic F e a tu r e so v e r th e N A M D o m a in

C L I M O v s 2 0 0 4

F R O N T S I N V E R T E D T R O U G H S

C U T - O F F L O W S

O P E N T R O U G H S

10

20

30

40

50

60

No. of D

ays

N u m b e r o f C u tO ff L o w - D a ys o v e r th e N A M D o m a in 1 9 6 7 - 2 0 0 1

1965 1970 1975 1980 1985 1990 1995 2000 20050

10

20

30

40

50

60

Day

s

1965 1970 1975 1980 1985 1990 1995 2000 20050

10

20

30

40

50

60

Day

s

1965 1970 1975 1980 1985 1990 1995 2000 20050

10

20

30

40

50

60

Day

s

N u m b e r o f O p e n T r o u g h - D a y s o v e r th e N A M D o m a in 1 9 6 7 - 2 0 0 1

1965 1970 1975 1980 1985 1990 1995 2000 20050

10

20

30

40

50

Day

s

Summary and Conclusions

1. A 35 year climatology of transient synoptic features indicates that NAME 2004 was characterized by:

a. Cold Front Days 200% of normal. b. Inverted Trough Days 70% of normal. c. Cutoff Low Days 90% of normal. d. Open Trough Days 170% of normal.

2. Inverted troughs provide 20%-25% of the summer rainfall received in NC and NE Mexico.

3. Rainfall with IV troughs peaks when the system is overhead in NC Mexico. Rainfall peaks in Western Mexico when the IV system is 3° to 4° upstream: associated with MCS development ahead of IV troughs (downslope, weak capping).

4. IV Rainfall in NE Mexico peaks when the system

is 4° upstream and this may be related to disruption of the normal divergent trade system in the western Gulf of Mexico

5. In NE Mexico cold fronts provide about 6% of the normal summer rainfall (June to September).