Saturday's Uncertainty
With a generally mild and tranquil several days to come, the attention in my mind goes to this weekend. A weak area of low pressure will move through on Friday afternoon but there should be little in the way of any precipitation with it, maybe a few showers north of Philadelphia. It will be much like this past system last night and next week system that will scoot to our north tomorrow...no real big deal.
The next storm of potential significance may impact us on Saturday night and Sunday morning. This storm will be moving into the US West in about two days and will progress east across the country.
Our pattern in the atmosphere is generally zonal this week, which means that systems will generally move quickly across the country from west to east. This Saturday storm system will generally start out moving in a flat west to east pattern across the country. A fast moving and potent jet stream at higher latitudes will help spin this low up (potentially) into a stronger system, one that might bring some rain to the region Saturday night.
There is a difference in ideas with the storm among computer forecast modeling. The GFS (the graphic on the right up above) is trying to strengthen Saturday's storm as it comes east, bringing a soaker to the East Coast. The low takes a track that runs over our region and then along the Long Island coast, out to sea. As a result, the GFS storm provides more rain (and mountain and hilltop snow inland) for the Northeast, with rain for Philadelphia and vicinity.
The GFS is moving the surface low responsible for this potential storm along more slowly than the EURO, which makes a big difference in this storm's final evolution. The faster moving surface pattern with the EURO allows Saturday's storm to remain relatively weak and the upper jet energy does not catch up to the EURO depiction until it is off the coast. As you can see there is about a 400 mile difference in track position on Saturday night (time of the map forecasts up above), from south of Pittsburgh to south of Cape Cod. If the EURO fast mover plays out, the low bomb takes place offshore (leaving us with some wind on Sunday) and what we in Philadelphia end up with is showers Saturday, with some rain to our south.
Which one will play out? With our zonal pattern, typically systems travel cross-country more quickly so that lends some creed to the EURO forecast at this point. Given that this system will not be on US soil (and in the midst of US data sites) for another two to three days, uncertainty may continue in computer modeling until we close in on the event. The only uncertainty is between a soaking rain and a non-event of some showers...we'll see which one plays out.
The next storm of potential significance may impact us on Saturday night and Sunday morning. This storm will be moving into the US West in about two days and will progress east across the country.
Our pattern in the atmosphere is generally zonal this week, which means that systems will generally move quickly across the country from west to east. This Saturday storm system will generally start out moving in a flat west to east pattern across the country. A fast moving and potent jet stream at higher latitudes will help spin this low up (potentially) into a stronger system, one that might bring some rain to the region Saturday night.
There is a difference in ideas with the storm among computer forecast modeling. The GFS (the graphic on the right up above) is trying to strengthen Saturday's storm as it comes east, bringing a soaker to the East Coast. The low takes a track that runs over our region and then along the Long Island coast, out to sea. As a result, the GFS storm provides more rain (and mountain and hilltop snow inland) for the Northeast, with rain for Philadelphia and vicinity. The GFS is moving the surface low responsible for this potential storm along more slowly than the EURO, which makes a big difference in this storm's final evolution. The faster moving surface pattern with the EURO allows Saturday's storm to remain relatively weak and the upper jet energy does not catch up to the EURO depiction until it is off the coast. As you can see there is about a 400 mile difference in track position on Saturday night (time of the map forecasts up above), from south of Pittsburgh to south of Cape Cod. If the EURO fast mover plays out, the low bomb takes place offshore (leaving us with some wind on Sunday) and what we in Philadelphia end up with is showers Saturday, with some rain to our south.
Which one will play out? With our zonal pattern, typically systems travel cross-country more quickly so that lends some creed to the EURO forecast at this point. Given that this system will not be on US soil (and in the midst of US data sites) for another two to three days, uncertainty may continue in computer modeling until we close in on the event. The only uncertainty is between a soaking rain and a non-event of some showers...we'll see which one plays out.
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written by Tom @ 3/11/2008 07:59:00 AM
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