ATS/ESS 452: Synoptic Meteorology Friday 2/8/2013 Quiz & Assignment 2 Results Finish Thermal Wind MOS decoding (Assignment) New England weather

dv/dx  v is decreasing with increasing x (goes from positive to negative) dv/dx < 0 du/dy  u is increasing with increasing y (goes from negative to positive) du/dy > 0 Vort = neg - pos Vort < 0 Anti-cyclonic vorticity… clockwise rotation

Curvature Vorticity

3.We discussed three potential uses of potential temperature (θ). List them. Determine static stability An examination of the horizontal θ distribution is useful in locating frontal boundaries -- especially over uneven terrain where surface temperature differences may be caused by the terrain. Isentropic analyses  identify lift and/or moisture advection

Quiz #MeanMaxMin Quiz 1 (17 total points) 13 (76.5)1510 Quiz 2 (15 total points) 9.4 (63)117 Quiz 3 (15 total points) 8.5 (57) 12 (80) (scaled) 9 (12.5)8 (11.5)

MeanMaxMin 92.6 (77%) (85%)

Temperature Advection & Thermal Wind Backing Wind Profile: geostrophic wind turns counter-clockwise with height. In the NH, backing winds are associated with cold air advection. Veering Wind Profile: geostrophic wind turns clockwise with height. In the NH, veering winds are associated with warm air advection

*BUT… The link between veering/backing winds and thermal advection only applies to the GEOSTROPHIC wind Why is this?

The actual wind can veer or back due to other mechanisms that may not be related to thermal advection For example, in the PBL, friction can cause a departure from geostrophic balance. Notice below, that the inclusion of the friction has caused the sfc wind to blow towards the lower pressure. The influence of friction diminishes with height, and the flow becomes more geostrophic So in this example, how does the wind change with height? Implications? Frictional Veering

GSO sounding from 00Z 25 August 2008 What is the wind profile doing here? Clockwise with height Veering Wind Profile What type of thermal advection does this imply? Warm Air Advection (WAA) BUT… what can you say about the PBL? It’s relatively deep So this is likely frictional veering… no implications for WAA

GSO sounding from 00Z 27 August 2008 What is the wind profile doing here? Veering What type of thermal advection does this imply? WAA How about the PBL? Shallow, so the deep veering observed IS geostrophic veering. WAA is likely occurring. This is also consistent with the saturated atmospheric profile

MOS Model Output Statistics The MOS technique develops relationship equations from both observed and model forecast weather elements Produces statistical guidance for point locations throughout the model domain

KHPX-station ID, similar to METAR DT-Month/Day. / APR 16/ means all data below this is for April 16 th. Note that dates correspond with UTC time. HR-the hour that the forecast is valid (UTC). N/X-minimum or maximum temperature anticipated to occur within consecutive 12 hour intervals

TMP-surface temperature for that time DPT-surface dewpoint for that time CLD-cloud cover at a particular hour. It will be one of the following… OV: overcast (8/8 sky cover or totally obscured) BK: broken (>4/10 to <8/8 sky coverage) SC: scattered (>2/8 to 4/8 sky coverage) FW: few (>0/8 to 2/8 sky coverageor CL: clear skies

WDR-the wind direction in degrees (0-350) at a height of 10-meters. Add a zero to the end of the number to get the wind direction WSP-the wind speed (at 10-meters) in knots P06-the probability of precipitation (PoP) for a 6-hr period ending at the specified time (ex: 65 = 65% chance of rain from 6 hours previous to this point) P12-PoP for a 12-hr period ending at the specified time

Q06/Q12-quantitative precipitation forecast (QPF) categories for liquid equivalent precipitation. This means that snowfall is melted and a liquid equivalent is given. The format is “6 hour total (Q06) / 12 hour total (Q12)” up to the time specified. The numbers will value 0-6 and are shown as follows: 0: No Precip1: 0.01 to 0.09”2: 0.10 to 0.24”3: 0.25 to 0.49” 4: 0.50 to 0.99”5: 1.00 to 1.99”6: > 2.00”

T06-thunderstorm/conditional severe thunderstorm potential for a 6-hr period ending at time specified ex: 56/65 suggests that there is a 56% chance of thunderstorms BUT a 65% chance that IF thunderstorms form, they will be severe T12-same as above, but for 12-hr period ending at time specified

POZ-probability of frozen (sleet/freezing rain) precip, IF precipitation occurs POS-probability of snow, IF precipitation occurs TYP-precipitation type. If forecast says there is precip, it will be in this form S = snow Z = freezing rain/drizzile, ice pellets or anything mixed with freezing precip R = rain/drizzle or rain mixed with snow

SNW-snowfall categorical forecast amount for 24-hr period ending at the indicated time 0: no snow or trace expect (trace < 0.01”) 1: > trace to < 2” of snow 2: 2 to < 4” snow 4: 4 to < 6” snow 6: 6 to < 8” snow8: ≥ 8” snow

CIG-ceiling (lowest broken or overcast layer) height forecast 1: < 200 ft7: ,000 ft 2: ft8: > 12,000 ft or unlimited ceiling 3: ft 4: ft 5: ft 6: ft

VIS-forecast visibility 1: 6 miles 2: ½ to < 1 mile 3: 1 to < 2 miles 4: 2 to < 3 miles 5: 3 to 5 miles 6: 6 miles

OBV-forecast for type of obstruction to vision N = none HZ = haze, smoke, dust BR = mist FG = fog (visibility < 5/8 mile) BL = blowing dust, sand, snow