13-14 December 2016 heavy rain and severe weather event in the northwest By: Zubear Said

Motivation - To find out the why tornadoes occurred in such a rare location of the U.S

Motivation - Distinguish the difference between environments of where tornadoes generally develop compared with Oregon where the tornadoes occurred.

Motivation -To prove that CAPE does not need to be high in order to have convective activity going.

Methodology - Since this was a case where areas received excessive rainfall amounts, weather prediction center quantitative precipitation forecast will be used to see how much locations received.

Methodology - Since this was a case where areas received excessive rainfall amounts, weather prediction center quantitative precipitation forecast will be used to see how much locations received. - Alicia Bentley’s maps were used to diagnose areas of upward or downward vertical motion as well as located the origin of moisture.

Methodology - Since this was a case where areas received excessive rainfall amounts, weather prediction center quantitative precipitation forecast will be used to see how much locations received. - Alicia Bentley’s maps were used to diagnose areas of upward or downward vertical motion as well as located the origin of moisture. - Most importantly, used soundings to diagnose WAA, CAPE as well as shear. Also, to verify severe weather conditions, radar will be used to see convective activity in the area.

Key findings - Interestingly enough, locations in the northwest received nearly 30 cm especially in the mountains. Fig. 1 WPC QPF from 00z on 13th of Oct to 00z on 15th - PW values are quite high off the coast of Oregon and Washington with values nearing 40 mm. - This is indicative of an Atmospheric River. The feature extends all the way back to the sub-tropics into eastern Asia. Fig.2 Precipitable Water (PW) shown in color.

Key-findings Continued - Jet is amplified at this time. Northwest states are located in a jet exit region of a jet streak towards the poleward side. Indicative of upward vertical motion. Fig.3 250 hPa jet in filled colors. - Maximum vorticity occurs at the base of the trough so just downstream of the trough axis, expect there to be upward vertical motion due to CVA. Fig. 4 500 hPa vorticity.

Key-findings Continued - Veering of the winds indicative of WAA - An environment of low CAPE, high shear. Fig. 5 18z sounding from Salem, OR - Both soundings showed tornadoes within the area but the Shreveport sounding shows more CAPE but less shear Fig. 6 00z sounding from Shreveport, LA

Verification - Convective activity visible just off the coast of Oregon. Fig. 7 Radar at 12z on 14 October.

Conclusion - Main takeaway here is not always do we need high CAPE values to have tornadoes in the area. Plenty of shear will do the trick! -Despite the temperatures being on the cool side for Oregon compared with Louisiana, moisture transport from the sub-tropics is ample enough to provide somewhat warm, moist air into Oregon.

References "WPC QPF Product Archive." NOAA's National Weather Service. N.p., n.d. Web. 01 Dec. 2016. Bentley, Alicia. "Alicia M. Bentley's Real-time GFS Maps." Alicia M. Bentley's Real-time GFS Maps. Alicia Bentley, n.d. Web. 01 Dec. 2016. "Atmospheric Soundings." Atmospheric Soundings. N.p., n.d. Web. 01 Dec. 2016.