Models
GFS = Global Forecast System - Main US model forecasters look at. Forecasts out two weeks.
NAM - main short term US model forecasters use. Forecasts out 4 days (84hrs)
Euro = ECMWF model run out of Europe and second most used model by US forecasters - Forecasts out 10 days
UKMET - UK model - forecasts out 144 hrs
CMC = Canadian Model - forecasts out 240 hrs
GGEM = CMC
RGEM = short range version of the GGEM
JMA = Japanese model - forecasts out 7 days, but in 24hr increments
Nogaps = Navy Model - forecasts out 7 days
Dgex = in theory its supposed to be what the NAM would look like if beyond 84hrs. Initialized by the NAM, it uses GFS parameters after 84hrs.
ENS = ensembles. GFS, CMC and Euro have a 18-24 members in their ensembles. Basically, various what if scenarios. Helpful to look at their mean, where the majority of the members lie (east or west of operational).
SREF = short range US ensembles
WRF - hi resolution, 48 hr forecast - has the NMM member and the AVR member.
RUC - short range, hourly updates.
Geographical Locations (other than state abbrev)
BM = benchmark. 40N/70W. If a storm goes to the BM, usually means snow for NYC and NW suburbs. If it goes east, LI gets snow. West, we get rain.
ACK = Nantucket
DXR = Danbury
BDL = Hartford
LGA = Laguardia
EWR = Newark
ALB = Albany
OBX = outer banks
LI = long island
Apps = Appalachian Mts
GOM = Gulf of Mexico
GL = Great Lakes
CONUS = continental united states
OTS = out to sea
Meteorological terms
WAA = warm air advection or the moving in of warm air, usually over the top of cold air causing overunning precipitation, first in the form of snow, then sleet, then freezing rain, then rain
CAA = cold air advection or the reverse of WAA
CAD = cold air damming. If there is a high pressure to the north or N to E winds, its difficult to move the cold air as it dams up against the Apps
850 line = Around 5k feet (850mb) to 8k feet (750mb). snow forms. So if temps are below freezing at that level, its likely there is snow. However its possible that even higher up is warmer, which would result in sleet. Or if the surface temps are too warm, it could rain. But usually its a good indicator and should be used with the..
540 thickness line = aka the rain snow line. An indicator of the temps from 18k feet (500mb) down to the surface (1000mb). If its under 540, then its snow. If its above by a little, check the surface temps and 850 temps as it could mean wet snow. IF the 850 temp is above 0 and the thickness is below 540, then there could be a freezing rain event, so check surface temp. Here is a better explanation: 540 thickness
LLJ = lower level jet
MB = millibar, pressure of a storm. Most winter storms range from 980mb to 1000mb, with the lower being the stronger.
DP = dewpoint.
Radiational Cooling = when the warm air during the day escapes due to no cloud cover or wind
NCEP = national center for environmental prediction . You can get the us models, as well as all sorts of discussions and forecasts at the NCEP site
Snow ratios: typical snow ratio is 10:1 to 12:1 - as its easier to figure out and is reflective of our typical snow scenario - ground temps in the upper 20's and 850 temps -3 to -5. . So take qpf and multiply by the ratio. In cases where the 850 temps are -5 and we are below 25 degrees at the surface, I use either the 12 or 15:1 ratio. When the 850 temps are -8, it goes to 20:1, if temps are at or below 20. Warmer conditions mean the opposite - its rare but if the surface is above freezing, you can still accumulate if it snows hard enough, but that would be a 4:1 ratio or less. If its barely below freezing at 850 and 32 at the surface, I use either 5:1 or 8:1. Don't make the mistake of judging it on just surface temps - today it was in the low 20's and sleeted as the temps at 850 were close or above freezing and other layers were above freezing.
Pressure Approx. Approx. Level Altitude Altitude 850 mb 5,000 feet 1,500 m 700 mb 10,000 feet 3,000 m 500 mb 18,000 feet 5,500 m 300 mb 30,000 feet 9,000 m 250 mb 35,000 feet 10,500 m 200 mb 39,000 feet 12,000 m
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