City #9: Duluth, MN (KDLH)

The WxChallenge moves on from Newark, NJ to Duluth, MN. We are forecasting for Duluth (KDLH) from 11 March - 21 March for the 24-hour period 06 UTC - 06 UTC which translates to 1 AM CDT if you are looking at NWS Duluth, MN. Forecasts are still due by 00 UTC which is 8 PM local time (note the time change due to Daylight Savings Time beginning).

Duluth is located in Eastern Minnesota on the shore of Lake Superior. Now one might think that since it is located on a Great Lake that it is prone to lake effect. While this is true, there is another subtlety about Duluth. According to its Wikipedia page, it is the "San Francisco of the Mid-West" due to the proximity to a body of water and sloping terrain. So we have a combination of lake-effect and topographical influences to worry about given the right flow setup as I'll discuss later! That's pretty interesting, in my opinion.  Taking this into account and stalking the airport (KDLH WMO ID = 72745) we see that the portion of the city that borders the Lake is around 185 meters high, however KDLH is located to the northwest of the shore of Superior ( ~10 km away) and is located at an elevation of 435 meters.


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Given the orientation of the lake (southwest -> northeast) near the city and the fact that the land abruptly slopes up in elevation at the shore, upslope lake-effect or lake-enhanced precipitation may occur with easterly or northeasterly flow from synoptic-scale systems passing to the south and east. I wanted to find out the temperature of the lake, via the Great Lakes Observing System but the data are not available either due to the buoys being taken out for the winter or the lake froze over. Anyone have any clue which hypothesis is correct?

Large-scale Pattern:
A look at forecast 500-hPa heights according to the GFS shows that a trough will remain in place for the majority of the first forecast day, with a shortwave embedded within the flow towards the end of this week. This trough should persist until next week with generally dry and chilly air being advected by the wind from Canada. Next week a ridge builds out ahead of a developing cyclone lee of the Rockies which may allow for some above-average temperatures. This is all just from glancing at one run of one deterministic model so take it with a grain of salt... or the whole salt shaker depending on your outlook on life.


Tips/Comments for Duluth, MN (KDLH):

• Look at more than one deterministic model, especially side-by-side comparisons, toggling between models (Mode: Clickable Map), or even better- ensembles (SREF/GEFS Plumes, SREF Maps, GEFS Maps).
• WxChallenge's wind forecast is for sustained, not gusts. Instead of just looking at plan-view maps at or near the surface, try taking a look at forecast soundings. The measured wind speed is a 2-minute average. Gusts often occur because with heavy precip, higher momentum air can be brought down to the surface, i.e. winds reach the surface via more than just mixing, but unless they persist for about 2-minutes they won't verify. 
• Upslope lake-enhancement of precip may occur given easterly or northeasterly flow, the High Resolution Rapid Refresh (HRRR) is run out only for 15 hours from the initialization time, but they do have a "Great Lakes" domain option if you wanted to take a look at a high-resolution product if you had some questions about the very near-term part of your forecast.
• Really read the NWS Area Forecast Discussion (AFD). Those forecasters are experts in the intricacies of forecasting for Duluth.

 Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Duluth.
• Look at forecast model soundings for the period for KDLH.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the Duluth, MN WFO forecast discussion for KDLH.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover and fog.
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages. 

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes.

 
Tips/Comments for Forecasting Precipitation (inches):

• Take a look at some higher-resolution models (e.g. WRF)
• What does the WPC (formerly known as HPC) show?
• Take a look at some ensemble data (e.g. SREF (if no local option then try SPC's SREF page))
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

I don't know much about Duluth except for the fact that Bob Dylan was born there. So how do we successfully forecast for Duluth? The answer, my friend, is (quite literally) blowin' in the wind. If you didn't get that, culture yourself. Go Team SBU!!

City #8: Newark, NJ (KEWR)

The WxChallenge moves on to a city where we all have the chance to shine- Newark, NJ. This is as close as we get to forecasting for near SBU so enjoy it! At least we can rely on the expertise of our friends at our local WFO. We are forecasting for Newark, NJ (KEWR) from 25 February - 7 March for the 24-hour period 06 UTC - 06 UTC which translates to 1 AM EST if you are looking at NWS New York. Forecasts are still due by 00 UTC which is 7 PM local time.

I'm not going to spend too much time describing Newark because (a) it is so close, (b) you may have flown out of it before, and (c) very similar weather should be expected for there as for us so there is nothing varying conceptually. However, if you do have any questions please do not hesitate to comment on this post or email me.


View Larger Map

KEWR is just south of the center of Newark, NJ and just west of Jersey City which is just west of Manhattan. Stalking the airport, we see that it is located close to Newark Bay. So we are dealing with an environment almost identical to ours. I think that forecasting for KEWR will be challenging in the same ways that it is challenging for us especially with the fact that precip depends on track and intensity of cyclones and we look to have an active, progressive pattern on our hands for our first week of forecasting.

Large-scale Pattern:
Just like it will be a challenging forecast for us, so too will it be for Newark. A look at forecast 500-hPa heights according to the GFS shows that after today's ridge moves through, a trough sets up across the Eastern US bringing unsettled weather with each shortwave disturbance that forms. You can see this nicely by looking at a plot of the dynamic tropopause on the 2 PVU surface which shows the trough persisting for this entire first week of forecasting with the low-level vorticity plotted showing the GFS forecast for disturbances that, given enough moisture, may cause some precip. Another way of looking for forcing for ascent is to isolate the Q-vector convergence from the QG-Omega equation. Warm colors represent Q-vector convergence and Tuesday night's system stands out and then there is some weak forcing present other times during the week. So we've got a strong system to deal with Tuesday-Wednesday and general troughiness for the rest of the week.


Tips/Comments for Newark, NJ (KEWR) aka Home Sweet Home-ish:

• Look at more than one deterministic model, especially side-by-side comparisons, toggling between models (Mode: Clickable Map), or even better- ensembles (SREF/GEFS Plumes, SREF Maps, GEFS Maps).
• WxChallenge's wind forecast is for sustained, not gusts. Instead of just looking at plan-view maps at or near the surface, try taking a look at forecast soundings. The measured wind speed is a 2-minute average. Gusts often occur because with heavy precip, higher momentum air can be brought down to the surface, i.e. winds reach the surface via more than just mixing, but unless they persist for about 2-minutes they won't verify. 
• Really read the NWS Area Forecast Discussion (AFD). Some of you may even know the forecaster who wrote the short term  section.

 Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Newark.
• Look at forecast model soundings for the period for KEWR.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the New York, NY WFO forecast discussion for KEWR.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover and fog.
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages. 

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes.

 
Tips/Comments for Forecasting Precipitation (inches):

• Take a look at some higher-resolution models (e.g. WRF)
• What does the HPC show?
• Take a look at some ensemble data (e.g. SREF (if no local option then try SPC's SREF page))
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

Alright guys- Team SBU has a distinct advantage here due to us being a stone's throw away from the city! We know and live in this environment, however, Mother Nature is a tricky lady and threw a complicated pattern at us. We can handle it, Fuh-gedda-boud-dit! Go Team SBU!!

City #7: Burbank, CA (KBUR)

The WxChallenge moves on from Austin,TX to a city with a bit less weather. After all of the excitement we experienced personally with "Nemo" maybe forecasting for Southern California can be a way to relax. City #7 is the second city for the spring 2013 semester. We are forecasting for Burbank , CA (KBUR) from 11 February- 21 February for the 24-hour period 06 UTC - 06 UTC which translates to 10 PM local Burbank time (PST = UTC - 8) if you are looking at NWS Las Angeles/Oxnard . Forecasts are still due by 00 UTC which is 7 PM local Long Island time (EST).

Burbank, CA is located just north of Los Angeles and northwest of Hollywood. Imagine having to actually forecast for that area... I wouldn't want to make movie stars cranky, although there isn't much weather so perhaps it is a low-risk forecasting gig. Sorry, I digress.

To familiarize ourselves with the area, it is time to stalk the airport. KBUR is Burbank-Glendale-Pasadena or Bob Hope International Airport. Burbank is located on the eastern edge of the San Fernando Valley. Since it is in a valley, it is surrounded by higher terrain known as the Transverse Range. KBUR is close to the base of the Verdugo Mountains (highest peak = 953 m) to its northeast with the San Gabriel Mountains (highest peak = 3069) farther northeast past the Verdugos. The Santa Monica Mountains (highest peak = 948 m) and Chalk Hills (highest peak = 331 m) are close to the south of the city. A bit west of KBUR is the Simi Hills (highest peak = 652 m). Further from KBUR lies the Santa Susana Mountains (highest peak = 1142 m) to its northwest. Scroll around on the provided Google Map to get a better feel for the terrain.



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So why am I pointing out each small cluster of hills and mountains? Because when there are no synoptic players around to drive the winds, mountain wind systems prevail and will influence temperatures, especially when there is an absence of cloud and the valley and mountain are exposed to full solar insolation and nighttime radiative cooling.

To simplify things, I'll explain things in an idealized sense. Let's say you have a mountain peak and it slopes down into a valley. During the day, the mountain top receives more solar insolation because it is higher so the solar radiation isn't depleted by having to travel through that extra bit of atmosphere like it has to to reach the valley surface. So because the mountain top is receiving extra energy, its surface warms, air above the surface warms and rises freely because the environment at that elevation is cooler than that of the valley due to elevation differences alone. So because air is rising at the top, air rushes in from the valley to fill it. This phenomenon is known as anabatic wind or upslope-flow and occurs during the daytime on calm, sunny days. A similar phenomenon occurs at night, called the katabatic wind or down-slope/drainage flow. Similar physical principles are involved in the fact that at night the top of the mountain will radiatively cool, become more dense and a resulting downslope flow will develop. As the air descends, it will warm.

Unfortunately, KBUR is nestled within 2-50 km of a few hill/mountain ranges of varying altitudes. And these are coastal mountains with the Pacific lying less than 100 km to the southwest. So to summarize my thoughts on what to look for--

• Downslope warming from northeasterly flow. 
• Relatively heavy precip if system brings moist, southeasterly flow (i.e. ahead of a strong low that happens to be anomalously lower in latitude than normal... doubtful for February but we'll see...)
• Dry conditions from any offshore flow pattern

Large-scale Pattern:
A look at forecast 500-hPa heights according to the GFS shows that a ridging pattern will persist throughout our first week of forecasting for KBUR. High pressure dominates with no threat of precip. Easterly and Northeasterly flow could allow for high temps to get a littler higher due to downsloping.


 Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Burbank.
• Look at forecast model soundings for the period for KBUR.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the Las Angeles WFO forecast discussion for KBUR.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover and fog.
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages. 
• Downslope flow = warming through adiabatic descent!

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes. For example, easterly/northeasterlies can have localized warming effects at Burbank.

 
Tips/Comments for Forecasting Precipitation (inches):

• Take a look at some higher-resolution models (e.g. WRF)
• What does the HPC show?
• Take a look at some ensemble data (e.g. SREF (no local option so try SPC's SREF page))
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

Alright guys- time to blast some Katy Perry and Beach Boys, grab your stunna-shades (are those even still a thing?), and demand someone to fetch you two Fiji Waters (one for your tea-cup chihuahua) and forecast for Burbank, CA! Go Team SBU!

City #6: Austin, TX (KAUS)

Welcome back to forecasting for the WxChallenge! City #6 is the first city for the spring 2013 semester. We are forecasting for Austin, TX (KAUS) from 28 January - 7 February for the 24-hour period 06 UTC - 06 UTC which translates to midnight local Austin time (CST) if you are looking at NWS Austin/San Antonio forecast products. Forecasts are still due by 00 UTC which is 7 PM local Long Island time (EST).

Austin was the location for the most recent Annual Meeting of the American Meteorological Society earlier this month. Attending the AMS Annual Meeting or just the Student Conference is an amazing chance to see what the field of meteorology is really all about. If you are not a student member of the society, please consider doing so; a yearly fee of $20 can open up huge scholarship, networking, and educational opportunities. Okay, I'm off of my soap box and now you know why the WxChallenge is following their tradition of forecasting for the most recent AMS Annual Meeting city. Back to discussion forecasting.

Time to stalk the airport. KAUS is Austin-Bergstrom International Airport with a WMO ID of 74745. Austin, TX is located in south-central Texas, depending on how you slice up that oddly-shaped state, northeast of San Antonio, northwest of Houston, and south of Dallas & Fort Worth.
 



View Larger Map

So it is flat, in unimpeded (no real topography) proximity to the Gulf of Mexico, and pretty developed (more urban than not). So warm, moist air can likely surge up from the Gulf given strong southerly flow. We'll definitely keep that in mind.

Large-scale Pattern:
A look at forecast 500-hPa heights according to the GFS shows that the first player we will have to worry about is a large, digging upper-level trough causing a surface cyclone to form and strengthen lee of the Rockies. All of the models are showing this as it is in the very near-term. Ahead of this cyclone in the warm sector, there will likely be strong warm air advection off of the Gulf. This warm, moist air should allow for there to be a chance for some heavy rains with the passage of the cold front. Behind the cold front there should be clearer and cooler conditions. The models are showing predominately zonal flow for the remainder of the week. So we are starting Austin off with a bang but then things may be a bit boring.

What to watch out for (IMO):

• Amplified flow that allows strong southerly flow ahead of upper-level troughs to advect warm, moist Gulf of Mexico air into central Texas.
• Given quiet synoptic players, the evening dew point can act as a rough guess for the nighttime low (some forecasters use this as a first guess when they think MOS is bonkers). Therefore the wind direction may be a good indicator of humidity which may affect the nighttime temperatures, 
• i.e. southeasterly winds should be more moist which means a higher dew point which means a higher nighttime temperature and northeasterly winds will advect drier air which means a lower dew point which means the possibility for lower nighttime temperatures.

 Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Austin.
• Look at forecast model soundings for the period for KAUS.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the Austin/San Antonio WFO forecast discussion for KAUS.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover and fog.
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages.

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes. For example, southerlies may bring warmer Gulf air inland to Austin.

Tips/Comments for Forecasting Precipitation (inches):

• Take a look at some higher-resolution models (e.g. WRF)
• What does the HPC show?
• Take a look at some ensemble data (e.g. SREF (South Central option) or for a zoomed-in national look try here.)
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

Alright guys- grab your cowboy hats and boots and try to lasso up some great forecasts! If you ever have any questions or want to talk about AMS student opportunities please feel free to stop by my office in Challenger 121. I have candy. That is all. Good luck with KAUS!
 

WxChallenge Spring 2013!

Welcome back to the WxChallenge discussion site for the SBU team! I hope that you enjoyed your winter break and are ready to get back into the groove of point forecasting for cities across the United States. This semester is special for two reasons...

(1) We get to vote for the 10th forecasting city!
Isn't that pretty cool? Simply log in and input your top three cities' stations ID with the preceding "K" (or "P" if you are considering some Alaskan cities!) The list of valid stations are found here. Voting is done here and must be completed before February 7th! I'm totally voting for KISP, KLGA, and KJFK but that's because I'm in a New York state of mind.

(2) There is a tournament at the end for those who qualify!
The top 64 forecasters based on their combined fall and spring normalized scores are invited to participate in a tournament forecasting for the final city. The bracket will be posted here and there you can find additional rules about the tournament. Think you have what it takes?? Go for it this semester! Best of luck!

The Challenge
The contest begins on Monday, January 28th for Austin, Texas (KAUS). Forecasts are due by 00 UTC or 7 PM EST. Here is the schedule for this semester:

City	Identifier	Dates
Austin, TX	KAUS	January 28 - February 7
Burbank, CA	KBUR	February 11 - February 21
Newark, NJ	KEWR	February 25 - March 7
Duluth, MN	KDLH	March 11 - March 21
To Be Determined*	KTBD	March 25 - April 4  (Vote by 2/7!)
Wichita, KS **	KICT	April 8 - May 4

Source: http://wxchallenge.com/challenge/schedule.php

The rules haven't changed at all from the fall semester. We are still forecasting for the 24-hour period 06 UTC - 06 UTC. For each forecast you must submit a high temperature (F), low temperature (F), maximum wind speed (kts) and precipitation amount (in). Note that the wind speed is sustained, not gusts, and the precipitation amount is the cumulative liquid precipitation- so don't put 12 inches if you think it will snow a foot!

For more detailed info and guidelines on the scoring system please see the WxChallenge website. Motivational statement: first and second place forecasters for each category receive trophies for every city, not just overall or tournament winners. We got close last semester with a few of our forecasters so let's try to get some trophies this semester!

Below are a few useful resources however everyone is encouraged to log onto the Metlab computers and plot model data using nmap2, analyze soundings with BUFKIT, etc. Thanks for your enthusiasm and good luck-- let's go SBU!

Useful Links
Submit your forecasts: http://wxchallenge.com/challenge/submit_forecast.php

Current Analysis

-Satellite-
Global Satellite (NRL)

Regional Satellite (RAP/UCAR) 
NASA GOES (ESO)

Satellite (UW-Madison)

 -Surface-

Surface Obs (RAP/UCAR)
METAR (UWyo)

Surface Potential Temperature Map (UAlbany)

National Radar (NOAA)

Hydrometeorological Prediction Center (HPC)

-Upper-levels-

Upper Air (NCEP)

Soundings (UWyoming)

-Tropical & Severe Wx-

National Hurricane Center (NHC)

CIMMS Tropical Cyclones (UWisc-Madison)

Storm Prediction Center (SPC)

Forecasting Resources

WxForecaster

Twisterdata

PSU E-wall

NCEP Model Page 
NSSL WRF Page
University of Washington Site of Loops
MOS (Text)

Archived Data

ESRL Interactive Plotting & Analysis
North American Historical Wx Maps (UWashington)

Radar and Satellite (UCAR)

SPC Storm Reports & Mesoanalyses

Monthly Climate Normals (NCDC)

City #5: Syracuse, NY (KSYR)

Welcome to the final WxChallenge forecasting city for the Fall 2012 semester!!! We are almost done and then get a well-deserved forecasting vacation over winter break! This city is a lot closer to home. However, the weather is significantly different up in good ol' Syracuse, NY compared with Long Island which just proves that New York is huge and meteorologically diverse. You'll respect that fact once we get forecasting.

We will be forecasting for Lake-effect-opolis... oh, I mean Syracuse, NY (KSYR) 26 November through 6 December 2012. Forecasts are due by 00 UTC each evening which is still 7 PM local time. We are still forecasting for the 24-hour period 06-06 UTC which is 1 AM - 1 AM EST  if you want to look at NWS Binghamton products (hooray for being in our own timezone!).

Syracuse, NY is known for its snow and has a reputation as being the snowiest city in the US. KSYR receives 121.2 in (308 cm) of snow on average every year mostly due to lake-effect events and nor'easters. For a few more interesting facts, I recommend checking out the Wikipedia page on the city. Syracuse is located in central New York State, straddling I-90, southeast of Lake Ontario (the big, important player), southwest of Lake Oneida (the little guy), and just northeast of most of the Finger Lakes. There is no real topography to worry about; parts of the city are hilly while the rest is mostly flat. The real focus as a forecaster is that warm Great Lake.

Taking a moment to stalk the airport, KSYR is located on the northern edge of the city (even closer to the lake). The ASOS station ID number is 72519. 



View Larger Map

Just to review what the climate normals are-- cold and snowy. The average temperature for the entire month of December is 30 F with an average snowfall amount of about 35 inches. More climate data and records can be found here.  

Before talking about forecasting tips, I think it is a good idea to have a review of lake-effect precipitation. I'm not sure if everyone has had this as part of their coursework or not. It's a fun concept to review, anyway!

Lake-effect Review

In a nutshell

• Cold, dry air blows over a warm lake and destabilizes due to fluxes of heat and moisture into the air and rises, forms clouds and can precipitate.

Ingredients

•  Cold, dry air and a warm, ice-free lake
• Air: the colder, the better for fueling lake-effect storms. If you have a polar air mass with temperatures around -5 C to -25 C (23 F to -13 F) then if you warm the air below it, it will rise until it stabilizes, or cools during ascent until it is equal to the temperature of the environment. So the cooler that is, the more the parcel will rise because the environmental lapse rate is greater than the moist adiabatic lapse rate (7 C/km). For forecasting, the 850 mb temperature is used to represent the air temperature.
• Lake surface: the warmer, the better for fueling lake-effect storms. The Great Lakes remain mostly ice-free throughout the winter which will allow for fluxes of heat and moisture to occur from the lake surface to the adjacent air. Especially since it is only late November, the lakes are open. The current temperature of Lake Ontario is about 48 F. 
• Air-Lake Temperature Difference: Previous studies have shown that a difference in lake surface temperature and the 850 mb temperature should be at least 10 C for synoptically-forced events (e.g. there's a shortwave trough passing through) or at least 12 C in general. 

• A long lake parallel to the wind
• This is known as the lake having a large "fetch". We are trying to get fetch to happen, regardless of what Regina wants. Anyway, the longer the wind blows over the warm lake, the more the air can warm up and by the relationship of the saturation vapor pressure, more water vapor can evaporate into it so it will be warmer and moister and rise more and be more likely to precipitate. So air residence time over the lake is important which depends on the near-surface wind direction.
• More on fetch and lake-effect bands
• Lakes usually aren't perfectly circular and tend to have a long axis and a short axis, just like Lake Ontario. Lake-effect bands tend to be stronger when the wind is parallel to the longer axis with a larger fetch, but bands can still form and precipitate heavily when oriented with the shorter axis of the lake.
• Bands come in a variety of flavors. There's shore-parallel bands, wind-parallel bands, over-lake bands, vortices, etc. 
• Bottom line: bands will form if most of the ingredients are present and not only if the wind is exactly parallel to the long-axis of the lake. 

• Low directional wind shear
•  Lake-effect is shallow, only reaching 2-3 km. But too much directional shear (change in direction of the wind with height) can weaken or disorganize them as they attempt to propagate from the lake where they originate. 
• Forecasters look at the 700 mb wind as the "steering wind" that tells where the bands will propagate. Some studies have shown that if there is a directional shear between the boundary layer (10 m wind) and 700 mb wind of less than 30 degrees then the band will propagate in the direction of that wind.

The lake-effect process in an expanded nutshell

 A figure from the lake-effect chapter from Severe and Hazardous Weather: An Introduction to Meteorology by Rauber, Walsh, and Charlevoix.

• Cold, dry air blows from the land to over the lake. It experiences a decrease in friction over the smooth lake surface and accelerates. This creates a divergence at the surface so air sinks from above to fill in the void, hence why the upwind shore of the lake usually has clear skies. The lake exchanges heat and moisture with the air, warming up the air and adding moisture. The air rises due to being positively buoyant and forms clouds, but the most clouds are formed when the air decelerates and converges with the shore. Got it now? Awesome. 

Forecasting for lake-effect snow

•   Extra Tools

• BUFKIT on the metlab computers
• You can also retrieve text data here of forecast soundings that are displayed in BUFKIT. It's a little hard to read, but the data for each sounding every hour is there for NAM, GFS, RUC-- just click on Syracuse.
• SPC Mesoanalysis
• They actually have lake effect parameters you can plot under Winter Weather --> Lake Effect Snow 1 and Lake Effect Snow 2 but data is not available for future forecast times.
• Lake Effect Snow 1 plots boundary layer RH (because you want it to be moist over the lake), and the sfc-850 mb temperature difference (can take as a first order analysis if you don't have the lake temperature, but oh wait you do!)
• Lake Effect Snow 2 plots the boundary layer wind in barbs and streamlines (sense of wind direction and speed) as well as convergence (look for a maximum convergence on the shore for more uplift for the band).

• Review of Ingredients

 

Table 1 from Niziol et al. 1995.

•  Due to KSYR being located where it is, northwesterly flow off of Ontario with low directional shear should result in a lake-effect band reaching the ASOS station. The synoptic setting for this is a high pressure system to the west and a low pressure system to the east.

Resources

• An amazing study by Niziol et al. 1995 entitled "Winter Weather Forecasting throughout the Eastern United States. Part IV: Lake Effect Snow" provides a climatology of lake-effect snowstorms, a thorough overview of the processes involved in band formation, and forecasting tips. (If you can't access it via that link, search through Web of Science or e-mail me for it.)
• Most synoptic or mesoscale textbooks include a chapter on lake effect. I have a few in my office (Challenger 121) if you would like to borrow one. I swear I don't bite and I even have a stash of holiday candy to share in addition to weather books. A basic textbook I used to first learn about lake effect is Severe and Hazardous Weather: An Introduction to Meteorology by Rauber, Walsh, and Charlevoix.
• If you have time, make a free account (if you haven't done so already) and go through a MetEd module on lake effect.

Okay, now that you are all experts in lake-effect precipitation processes we can return to our originally scheduled programming!

Large-scale Pattern:

A look at forecast 500-hPa heights according to the GFS shows that a shortwave trough will help form a coastal low and the associated precipitation is not expected to reach KSYR. However, the pattern is conducive to west-northwesterly winds in the early period so before the drier air mass behind the trough moves in, there is a threat of lake-effect snow showers.

Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future. To do this quickly, check out the WxChallenge page for Syracuse.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Syracuse. Beware of high pressure to the west and low pressure to the east inducing northwesterly flow over Lake Ontario!
• Look at forecast model soundings for the period for KSYR.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the Binghamton, NY WFO forecast discussion for KSYR.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover and fog. Cloud cover is more of an issue for Syracuse and I bet you are sick of fog from forecasting for Astoria.
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages.

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes. For example, northwesterly flow may induce lake-effect bands that could reach Syracuse.

Tips/Comments for Forecasting Precipitation (inches):

• Take a look at some higher-resolution models (e.g. WRF)
• What does the HPC show?
• Take a look at some ensemble data (e.g. SREF)
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

Okie dokie, that's all I have to say as we begin forecasting for Syracuse. It's nice to be back in our home state but the whole threat of lake-effect has me nervous! If any of you have any questions or comments, please e-mail me or comment on this post. I hope you all enjoy forecasting for this exciting city and then enjoy your winter breaks! Take care and best of luck forecasting! Go SBU!  

City #4: Astoria, OR (KAST)

*** The WxChallenge changed the city from North Bend to Astoria. We are forecasting for Astoria (KAST) not North Bend (KOTH). ***

Hi guys! Today not only do we resume classes after missing a week due to Sandy but we begin forecasting for a new city for the WxChallenge. Thank you all for your cooperation in submitting forecasts despite region-wide power losses. Our team score didn't suffer... too... badly... *sigh* If you are still without power like I am, please do your best to come to campus and use the Metlab computers or your personal laptop to forecast for Astoria. Selecting "Guidance" for multiple days results in 5 error points for each additional day it is used (you get one freebie) so I'd rather not have us accrue error points again.

We will be forecasting for Astoria, OR today through November 15th. Forecasts are still due by 00 UTC but since we've changed the clocks forecasts are now due by 7:00 PM local time! We are still forecasting for the 24-h period of 06-06 UTC for Astoria which is 10 PM - 10 PM local or PST if you are looking at forecasts from the NWS Portland Office for Astoria Regional Airport.

Astoria is found in northwest Oregon and is situated right on Youngs Bay which is off of the Columbia River that empties into the Pacific Ocean. So needless say this is a marine environment. And during this time of year... it's likely going to be wet.

Taking a moment to stalk the airport where the ASOS station (Station ID= 72791) is, we can see that it is located right on the water. In addition to the marine environment, there is significant topography in the region like Mt. St. Helens that is ~120 km due east and some coastal mountains to the south-southeast and northeast.




View Larger Map

Just to briefly mention what climate normals are, for this time of year it's usually pretty gray (yes that's a climate parameter) with a small diurnal temperature range with highs in the mid-to-upper 50's and lows in the mid-40s. Usually during this time of year, the region starts getting slammed with pacific extratropical cyclones. Let's see how things shape up for our forecasts.

Large-scale Pattern:

A look at forecast 500-hPa heights according to the GFS shows that a trough is expected to "slam into" and "dig deeper" (I prefer to say it with flair instead of "progress into the region" and "increase in amplitude") this week. That should bring a larger chance of rain and slightly cooler temperatures to Astoria.

What to watch out for (IMO):

• Upper-level lows coming from the Pacific and Gulf of Alaska.
• Fog is seen to develop overnight if the winds are light enough and no significant synoptic system is affecting the area so early evening dew points right before you submit your forecast may be a good guidance for a nighttime low.

 Tips/Comments for Forecasting in General:

• Check out the current weather first via satellite, radar, surface observations, METAR, etc. You have to understand the present before you can look to the future.
• Get a feel for general pattern from NAM, GFS, etc. (available from here and here, for example). Identify the general pattern of low and high surface pressure systems and their progression, temperature advection at 850 mb, moisture at 700 mb, vorticity at 500 mb and the general jet structure at 300 mb. Make sure you are focusing your attention on Astoria. Beware of cold fronts during this time of year.
• Look at forecast model soundings for the period for KAST.
• Compare your idea for values with MOS (model output statistics).  Keep in mind these are instantaneous output values and you can always have values above/below that between output times. 
• Read the Portland, OR WFO forecast discussion for KAST.

Tips/Comments for Forecasting for High/Low temperature (Fahrenheit):

• Recall such basics as nighttime radiative cooling and daytime solar radiative heating, both of which are affected by cloud cover and fog.
• Frontal passages can affect your temperature forecast. Pay attention to the forecast timing of such frontal passages, especially cold fronts for Astoria.

Tips/Comments for Forecasting Wind Speed (knots):

• NWS outputs wind speed in mph so if you are comparing your forecast value to theirs keep that in mind. Otherwise the models output wind speed (WSP) in knots.
• Look through METAR or surface obs for wind direction and temperature changes. For example, westerlies may bring warmer oceanic air inland to Astoria.

Tips/Comments for Forecasting Precipitation (inches):

• Take a look at some higher-resolution models (e.g. WRF)
• What does the HPC show?
• Take a look at some ensemble data (e.g. SREF or for a zoomed-in national look because the PSU e-wall doesn't have a zoomed-in Pacific Northwest option, try here.)
• Most products you will be looking at will output the QPF in inches already so no conversion is necessary.

Alright guys- grab your solar lamps and cups of hot tea (or Starbucks since we are sort of close to Seattle) and get to forecasting! Hopefully we can all forecast fully for Astoria without some devastating storm knocking out our power... *cough* *cough* Nor'easter *cough* *cough* If you have any questions or want to discuss anything, feel free to comment on this post. Best of luck forecasting! Go SBU!