# Presentation: 000312

## North American Drought Briefing

- Climate Prediction Center/NCEP/NOAA
- September 13th, 2007
- _[http://](http://www.cpc.ncep.noaa.gov/products/Drought)__[www.cpc.ncep.noaa.gov](http://www.cpc.ncep.noaa.gov/products/Drought)__[/products/Drought](http://www.cpc.ncep.noaa.gov/products/Drought)_

## Outline

- Precipitation and soil moisture patterns
- Regional hydrological conditions
- Atmospheric support
- Analysis of extreme events
- Historical perspective from SPI
- GFS week1/week2 drought outlook

## Precipitation Anomaly 

- The dipole with  wet S-Plains  & Dry SE  persists from May-August
- _August:_  a 3-cell P pattern
- 1.Wet N-Plains
- 2. The  S-Plains-SE dipole is slightly  weaker
- 3.  Weak monsoon

## Precipitation Anomaly - Weekly

- _August:_
**Erin (TS) **8/15 - 8/19  **Dean (Cat. 5**) 8/13 - 8/23   **Felix (Cat. 5)** 8/31 - 9/5

**(From Climate Review)**

- Erin

- Dean

- Dean

- Influence of tropical storms

## Soil Moisture Anomaly 

- Soil Moisture Anomaly

- Ensembles
- AUG 2007

- JJA 2007

- Dipole feature persists

## Soil Moisture Change

- _August:_
- S-Plains – decrease
- N-Plains – increase
- SE – not much change
- SW - increases

## Runoff Anomaly Ensembles

- August 2007

- JJA 2007

- Less runoff over the SE and more over Oklahoma

## Long-Term Perspectives

## Evaporation Anomaly

## Regional Time Series: S-Plains

- Anomalies of P, E and SM suggest evidence of SM-Atmos. interaction over S-Plains

## Regional Time Series: SE

- Atmospheric condition dominates in SE

## Strong GPLLJ

- Weak GCLLJ
- Heavy P over the N-Plains
- Light SW monsoon rainfall

## Surface Air Temperature Anomaly (RR)

- AUG 2007

- JJA 2007

- Cooling S-Plains
- Warming Central-East

- Cooling S-Plains
- Warming Elsewhere

## (b) GPLLJ – Qv Anomaly

- (a) P (90-100W) August 2007

- A good correspondence between GPLLJ  &  P over the  N-Plains

**Notes:**
A good correspondence between the GPLLJ and the P over the Northern Plains

## Great-Plain Low-Level Jet (90-100W)

- AUG 2007

- JUL 2007

- P Anomaly – JUL 2007

- P Anomaly – 20-26 AUG 2007

- N-Plain P
- GPLLJ extended north

- S-Plain P
- GPLLJ had a maximum over Texas-Gulf

## From Climate Review AUG 2007  

- Convection over the E Pacific

- The Gulf & the Caribbean continues to be slightly warm

**Developing a cold event**

## The  3 cell P pattern in August has strong projection on the 

- The  3 cell P pattern in August has strong projection on the
-  First REOF for JJAS

- There is no tropical convection associated with it except negative OLRA in the tropical Pacific as indicated by the composite of OLRA based on RPC 1

- REOF 1 JJAS

- Possible soil moisture influence ?

## A possibility ?

**SM anomaly over S-Plains for JFM (open circles)**
**And P anomaly over the N-Plains for JAS (solid line)  **

- S-Plains: 31-35N,95-105W
- N-Plains: 36-45N,90-100W

**Over the S-Plains, P (JFM) anomaly was above 1 std and  positive SM anomalies persisted through spring and early summer. That may contribute to the rainfall over the N-Plains .   **

**A possibility ?**

## GFS Forecasts

- CPC Real-Time Precipitation Analysis                    7-day accumulation              12Z03Sep – 12Z10Sep 2007

- GFS week1 forecasts made  02Sep2007

- GFS week2 forecasts made 27Aug2007

- _Weekly Mean Anomaly Sep 03 – Sep 09 2007_

- The first week of Sept,
- P over the Great Plains, dry over the SE
- P over SW due to TC

- The GFS NAEF fcst captures the P pattern in general

## GFS Week1/Week2 Forecasts Made 10Sep2007

- Dipole pattern  persists

- Week1-Expecting more P over Southern
-              US, dryness over the N-Plains
- Week2- 3 cell pattern returns

**P fcsts**

**SM fcsts**

- week1

- week2

- week1

- week2

## GFS Forecast Verification – Soil Moisture

- Week1 Forecast Made 26Aug2007

- Week2 Forecast Made 19Aug2007

- Verification    27Aug2007-02Sep2007

- Errors corresponding to large uncertainties

## Composite of P for ASO for cold events from historical data 

- P composite for the ENSO cold phase – suggesting less P over the Southern US.

- If  this cold ENSO event intensifies.....

**Composite of P for ASO for cold events from historical data **

## Summary

- The dipole features of dry SE and wet S-Plains established in April, persisted to now, alleviated in August.
- The E over S-Plains are SM-control; in the SE atmospheric condition control.
- The strong GPLLJ enhances the N-Plains rainfall and the weak GCLLJ decreases the monsoon region rainfall.
- Forecasts show the dipole pattern will keep persisting but less severe.