Posted by
Robert Smith
at
Tuesday, February 9, 2010
Weather Graphics... Click on Images To Enlarge
| Watches and Warnings/Traffic /Airport Delays/ This Day In Weather History /NJ Road Conditions/ NJ Power Outage Map
Live Coverage Begins Wednesday Morning at 5AM
Criteria for Watches Warnings and Advisories| WATCHES | A Watch tells you that conditions are favorable and there is a pretty good chance that the event may happen. When a watch is issued begin making preparations for the upcoming event. Listen to your local media to know when warnings are issued. Watches are intended to heighten public awareness of the situation. | | WARNINGS | A warning means that a certain weather event is IMMINENT.Measures should be taken to safeguard life and property IMMEDIATELY | | ADVISORIES | Advisories are issued when events are expected to remain below the warning criteria, but still cause significant inconvenience. Most common in association with snow events. |
| WINTER SEASON WATCHES/WARNINGS/ADVISORIES |
SNOW ADVISORY -- A Snow Advisory will be issued when 3-5 inches is expected to fall. *Check with your NWS office for local snowfall requirements. BLOWING SNOW ADVISORY -- A Blowing Snow advisory will be posted for events in which visibility is intermittently 1/4 mile or less. FREEZING RAIN / FREEZING DRIZZLE ADVISORY -- This requires that hazardous driving conditions be taking place and/or up to 1/4 inch of freezing rain on tree branches and/or if power lines break. WINTER WEATHER ADVISORY -- A Winter Weather Advisory will be issued if conditions warranting two seperate winter advisories are met. WINTER STORM WATCH -- A Winter Storm Watch may be issued when conditions are forecast to meet the criteria for more than one warning with in the next 36 hours. A watch for a single winter weather event does not exist, for example a Wind Chill Watch or a Heavy Snow Watch. Just the same, if a forecaster thinks there will be significant snow and ice tomorrow, he/she will issue a Winter Storm Watch. WINTER STORM WARNING -- A Winter Storm Warning will be issued if conditions are forecast to meet the criteria for two seperate warnings in the next 12-24 hours. Example: If you have Heavy Snow Warning conditions along with Wind Chill Warning conditions, a Winter Storm Warning will be issued. BLIZZARD WARNING -- A Blizzard Warning will be issued when the following conditions are forecast to last at least 3 hours. Falling and/or blowing snow frequently reducing visibility to < 1/4 mile AND sustained winds or frequent gusts > 35 mph. ICE STORM WARNING -- An Ice StormWarning will be issued if freezing rain/drizzle is occurring with a significant accumulation of ice (more than 1/4 inch) or accumlation of 1/2 inch of sleet. HEAVY SNOW WARNING -- A Heavy Snow Warning will be issued if 6 or more inches of snow is expected in a 12 hour period.  Forecast Discussion through the Week Ahead( Get ready)!
 The image to your left is the approximate position of the the storm Track for Wednesday. The image to your Right is the NAM Night Run of the Total Snowfall expected over the NJ/NYC metro area through 84 hours. Click the Image to enlarge it. Now remember this is the model guidance and where it may  suggest the heaviest snowfall to be over Central and Southern NJ extending back through the Delmarva and SE PA and MD. Again these will be the areas that may be impacted the most as banding of snow sets up across these areas. Also to note that this model is further south with the heavier snow .
 This image to your left is the GFS model guidance out to 120 hours. Again the focus for heavy snow pushing beyond 10 inches stretches across all of Northern and Central NJ into the City with amounts increasing to a foot and a foot and a half over NE and Eastern PA..including SE PA and the Northern Half of DE the Chesapeake and MD. The reason for the image difference between the two models is simply the way the upper level low develops and it may be and the strong transfer of energy to the coast. The frontogenetic forces between the strong coastal thermal gradient and the bombing surface low offshore will create strong lifting and buoyant air to the left of the surface track ,as is often the case in major storms with well developed features from the surface to the upper troposphere. This will often create deformation zones in the comma head of the departing storm as seen on satellite features as the storm begins to occlude. Deformation,or vertical and horizontal stretching of wind can have lingering heavy snowfall as the storm is exiting to the NE.  The newer model data coming in from last night is showing a concentrated inverted trough that will develop offshore Delmarva at the same time the 850 and 700MB low is offshore overhead. Pressures will begin to drop drastically and NE winds and frontogenetic forcing between the surface and mid levels will produce enhancement to the snowfall in bands from the Delmarva upto Northern and Central NJ and into NYC. Here's an example from current last night's Run of the WRF/NAM..  Showing the frontogenesis and heavy burst of snow and increased wind Wednesday afternoon and Evening across The Delmarva upto NYC and then into Southern Connecticut...
If this is correct again the placement of bands in the comma head of the deepening surface low will spread back or redevelop heavy or moderate snow in these areas... Again these are features we will have to keep our eyes on. Winds will increase and Blizzard conditions may become imminent for locations particularly along the Delmarva upto Southern NJ Coastal areas...The mid and low level forcing and momentum would cause any mixed precipitation over the coast to turn back to snow! The reason I am bringing all of this up is that where ultimately the heavy snow often 1-3 inch accumulations per hour can be accompanied by mesoscale phenomena such as thunder-snow or inverted troughs that will only be able to be now-casted as the event begins as these features will impact certain areas while robbing others. Unlike the previous HECS(Historic East Coast Snowstorm) on Saturday, this storm again will be far reaching and discrete mesoscale bands North of the developing low pressure system off the coast. This will lead to CSI perhaps. CSI is conditional Often found during large comma shaped winter storms can form over periods of several hours and this will often dictate where frontogenetic forcing will be greatest. I know I am getting into the heart of meteorology here...and the bottom line of heavy snow will wax and wane depending on some of these now casted conditions that will really not become apparant until 12-24 hours out and even still in the now cast of the storm as the low begins to bomb out off the coastal waters.
Unlike the previous storm system I would like to draw your attention to two types of storms that are classified coastal storms over the Northeast Corridor. Named after James E. Miller a meteorologist who did extensive research in this area in the 1940s. In short, Miller's research has given meteorologists today a way of describing two different ways Mid-Atlantic storms form. He appropriately named them,"Miller A" and "Miller B" storms.
 A Miller A type snowstorm has a low which originates in the Gulf; it intensifies and races up the east coast. EX: Superstorm 1993, Blizzard of 1996. These tend to be more widespread in area BUT can be less favorable for historic snows in New England. However, they can clobber portions of the Mid-Atlantic.
 A Miller B type snowstorm has a primary low over the Appalachians while a new, secondary, and more powerful low spins up along the Gulf Stream waters off the coast of NC. It intensifies and depending on its track can clobber areas of inland or coastal New England. These are less widespread in terms of area and usually miss the Mid-Atlantic. EX: Blizzard of 2005.(this type of setup is forecasted is Forecasted for Wednesday) 6-10 Day Weather Outlook Window Graphics(click on images to enlarge)
8-14 Day ECMWF/GFS Ensembles Plus 14 Day GFS NAO and AO Forecasts
8-14 Day Weather Outlook Window Graphics(click on images to enlarge) |
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1 comments:
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