1. - 200 hPa geopotential heights in the GDAS analysis are lower than in CDAS over most of the planet except the North American continent, particularly from 30 o N to the South Pole. -200 hPa geopotential heights are consistently lower for GDAS compared to CDAS since at least January 2005 over the global Tropics. -Relatively good agreement is noted between the anomalous Precipitation in the CDAS and the CAMS_OPI estimates although CDAS is drier than the observations over the northern & equatorial Indian Ocean. -GFS precip. is much too strong in the Atlantic and eastern Pacific ITCZs at all forecast projections and is much less than the satellite estimates over much of Southeast Asia. During the preceding several months, this relative dryness in the model fcstswas observed further east over the adjacent oceanic region. The GFS global mean precip. is consistently abut 25% higher than GPCP -Vertical velocity and upper-level divergence fields are consistent with the precipitation differences over the Pacific near-equatorial regions in the GDAS/GFS. - In general, the CDAS temperature anomalies are within 1K of the observed anomalies. In contrast with previous months, the CDAS anomalies are slightly warmer than the CAMS data. October 2005 Summary of CDAS/GDAS/GFS

2. 200 hPa geopotential heights in the GDAS analysis are lower than in CDAS over most of the planet (particularly from 30 o N to the South Pole. Very small differences are noted Between 30 o – 70 o The magnitude of the differences over the Tropics is equivalent to about 1 standard deviation of the CDAS monthly means over the 1971-2000 base period. This is the same basic pattern since March 2005.

3. Time series of 200 hPa heights for GDAS and CDAS over the Tropics indicate that heights are consistently lower for GDAS compared to CDAS since at least January 2005, and that this difference occurs over land as well as ocean, although the difference is largest over the oceans.

4. The zonal 200 hPa hgt errors in the GFS grow with the length of the forecast projection. During Oct 2005, negative hgt errors in excess of 10m are generally observed for the day-3 forecasts and beyond. Errors in excess of 0.5 std. dev. (right panel) are observed after Day-3 in the Tropics that grow with forecast projection, up to 2 sigma at Day-14.. http://www.cpc.ncep.noaa.gov/products/fcst_eval/html/maps_mrf.html

5. The CDAS precipitation is substantially weaker over much of the Atlantic and Pacific ITCZs, the near-equatorial Indian Ocean and the Maritime Continent compared to satellite estimates of precipitation amount.

6. Relatively good agreement is noted between the anomalous Precipitation in the CDAS and the CAMS_OPI estimates although CDAS is drier than the observations over the northern & equatorial Indian Ocean.

7. GFS precip; is much less than the satellite estimates over much of Southeast Asia. During the preceding several months, this relative dryness in the model fcsts was observed further east over the adjacent oceanic region. Precip. is much too strong in the Atlantic and eastern Pacific ITCZs at all forecast projections.

8. GFS underforecast the precipitation significantly at Day-5 and beyond during Oct 2005 over the East Coast of the US. Record rainfall and attendant flooding occurred over parts of the mid-Atlantic and New England during the middle of the month. For The Day-10 & Day 15 forecasts, the model was moderately wetter From the Ohio River Valley to the Rockies and drier

9. The CDAS OLR is cooler over the extratropical portion of the NH continents compared to observed OLR and warmer over much of the Tropics north of the equator. GDAS OLR is substantially closer to the observed OLR compared to CDAS, and the differences with observed OLR are almost completely positive.

10. The evolution of near-equatorial OLR anomalies during Feb 2005 through October 2005 in CDAS shows negative anomalies for the entire period near the date line. That contrasts with the observed OLR which indicates negative anomalies there sporadically during that period. Note that GDAS anomalies are not plotted because a reliable climatology is not available from GDAS due to the many model changes that have occurred during the GDAS record.

11. The GDAS upward motion at 500 hPa is considerably stronger than CDAS over the ITCZs in the Atlantic (particularly so in August 2005) and Pacific which is consistent with the higher rainfall in the GFS over those areas compared to CDAS (see precip. figs – buttons below). This is also consistent with differences in the upper-level divergence (button below). CDAS precip GFS precip Divergence

12. GDAS vertical velocity (500 hPa) is consistently higher than CDAS over tropical land regions, in good agreement over the tropical oceans, although consistently lower there since April 2005. Both are in good agreement over the NH oceanic storm tracks.

15. CDAS 2m temperatures are generally 1-3K cooler over the land surfaces than is observed; regions where CDAS is up to 1K warmer than the obs. are generally in areas with high terrain. In contrast, GDAS 2m temps. are 1-3K warmer than CDAS over the majority of the continental regions.

16. In general, the CDAS temperature anomalies are within 1K of the observed anomalies; where they differ. In contrast with previous months, the CDAS anomalies are slightly warmer than the CAMS (station) data.

17. Global Mean precip from GFS is about 25% higher than GPCP.