1. A JUNE MONSOON? David L. Mitchell 1, Dorothea Ivanova 1 and David Gochis 2 1.Desert Research Institute, Reno, Nevada 2. National Center for Atmospheric Research, Boulder, Colorado Acknowledgment: We thank the people at NOAA/NESDIS, CIMSS at Univ. Madison, Wisc., the Navel Research Laboratory in Monterey and UNiSYS for hosting their products on the internet regarding satellite SSTs, total precipitable water, rainfall amounts and wind fields.

2. AZNM region cumulative normalized rainfall for periods having N. GC SSTs ≤ indicated SST. Time is implicit with increasing SSTs. Mean rainfall rates for the AZNM region for N. GC SST intervals of 0.5 o C based on five June-August seasons.

3. 7 July 2002 at 00 UTC, Total Precip. Water (TPW) 9 July 2002 at 00 UTC, TPW 11 July 2002 at 00 UTC, TPW 2.4 o C increase in N. GC SST over 2 days, reaching 29.8 o C.

4. 11 July 2002 at 00 UTC. 24 hour rainfall accumulation 15 July 2002 at 00 UTC. 24 hour rainfall accumulation 2002 AZ Monsoon Onset Period

5. Hypothesis Development: MM5 Modeling of the 1999 Arizona Monsoon Onset SST Evolution along the NW coast of Mexico

7. SST Dependence of Vertical Mixing Over the Northern Gulf Northern gulf SST: 26 o C SST below N. GC: 28 o C Northern gulf SST: 30 o C SST below N. GC: 30 o C Cross-Section A-B: Potential temperature 5 AM LST, day 3

8. Cross-Section C-D: Water vapor mixing ratio Northern gulf SST: 29 o C SST below N. GC: 30 o C Northern gulf SST: 30 o C SST below N. GC: 30 o C 5 AM LST, day 3

9. N. GC 26 o C; 28 o C otherwise N. GC 29 o C; 30 o C otherwiseN. GC. 30 o C; 30 o C otherwise Sensitivity of CAPE (Convective Available Potential Energy) to GC sea surface temperatures. Simulation time = 54 h; 11 pm LST. Yellow ≈ 1300 J/kg (CAPE) Orange ≈ 2100 J/kg Red ≈ 2900 J/kg Brown ≈ 3700 J/kg

10. 5 AM MST Day 3 5 PM MST Day 3 26/28 o C 29/30 o C 30/30 o C Dependence of CIN on GC SST

11. Conceptual Model of Moisture Advection Dependence on SST

12. Comparison of modeled and observed normalized rainfall rates for AZNM region, for modeled conditions in conformity with hypothesis

13. Temperature, Dewpoint, deg. C 3 km 2.5 km Altitude 1003001030 20 Examples of NAME Soundings over the GC; August Cruise

14. A June Monsoon? Blended SSMI/TRMM experimental rainfall estimates from NRL, Monterey

15. NG: 24.2 o CNG: 26.7 o C 16 June 200520 June 2005 SST & TPW

16. Wind fields suggest Gulf of Calif. moisture source 5 pm MST June 20 th, 700 mb 5 pm MST June 20 th, 850 mb

17. June monsoon summary

18. Food for Thought

19. What will happen next?

20. SUMMARY 1. MM5 simulations suggest that the marine boundary layer in the Gulf of California (GC) may be sensitive to GC SSTs. This MBL may act as a moisture source for monsoon rainfall over AZ. 2. The moisture source for the June period of scattered thundershowers affecting AZ, the Great Basin and Colorado appears to be the GC. This same pattern is common during the monsoon season. 3. Soundings over the GC during NAME are consistent with MM5 soundings. 4. Observations of SST, TPW, winds and rainfall during the “June monsoon” of 2005 appear consistent with the hypothesis developed from the MM5 study. 5. Since the GC appears to be warming at a rate of about 1.4 o C over the last 20 years, it is important to understand the role that GC SSTs play in monsoon dynamics.