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forecast

New weather pattern in the works?

After a long, long period of having a subtropical ridge anchored over the Southeast, it appears as though the long-wave pattern has finally shifted, with an upper-level ridge over the Desert Southwest and Plains and a trough over the Mid-Atlantic and Northeast. This will mean warmer weather for the Southwest and cooler, disturbed weather for the Mid-Atlantic and Northeast.

The next couple of weeks appear to be rather turbulent weather-wise as the Northern Hemisphere transitions into the winter weather pattern. Cut-off lows, blocking ridges, the potential for powerful low pressure systems and tropical systems near the U.S. are all possible as we head into October. With so many things possible in the future, forecasting anything beyond five days will be extremely difficult, so don’t be surprised if your extended forecast makes dramatic shifts this month.

The GFS model has been hinting at a powerful mid-latitude system in the 10-12 day range, which could mean some interesting weather and an awesome chase day for myself and Jason, but we’ll have to wait and see what pans out.

T.D. Sixteen forms south of Cuba, takes aim at the East Coast

This post might have to be updated if the NHC decides to upgrade Tropical Depression Sixteen to Tropical Storm Nicole later today.

Massive rains are in store for the East Coast tomorrow through Friday as T.D. 16 organizes just south of Cuba and heads towards the U.S. This storm is likely to be sub-tropical when it impacts areas from the Carolinas northward as it interacts with a stationary front just off the East Coast, but it could still pack tropical storm force winds as it progresses up the East Coast. One thing to expect with this system is heavy rain, on the order or 2-5+ inches, to cut a path up the interior East Coast along the eastern slopes of the Appalachians. Impressive wind shear associated with the right-front quadrant of this system will bring the risk of strong to severe winds and isolated tornadoes to the East Coast, but limited thermal instability caused by cold air damming will limit the severe potential with this system.

The significant rain totals will be mostly the result of large-scale forcing along a preexisting boundary when the tropical/sub-tropical system interacts with the stationary front within an atmosphere primed with moisture as P-WAT values are forecast to be in the 2-2.5″ range. Widespread flooding will be a big concern with this event, as the short-term drought conditions will cause the soil to struggle to absorb the rainfall. The past few day’s rain will help alleviate this effect, but not to a great extent.

I will be missing most of this event, as I have travel plans which has me driving north Thursday morning. *UPDATE: It looks like it will progress a bit faster than I anticipated… I’ll be driving through it almost the entire way.* Hopefully Jason will be able to cover the event and keep you all informed. Stay safe, and be sure to go over your flood preparedness and stay tuned!

(click to enlarge)

Drought cancel coming up for the East Coast?

With the models starting to get a consistent idea that heavy rainfall will be possible along the East Coast next week, could the drought-stricken coast have a sudden end to this summer’s dry run?

The GFS model is much more bullish than the ECMWF model when it comes to rainfall… it has a slightly slower tropical system with a track that’s further west than the ECMWF. Most of this tropical precip. north of VA comes in the 11-15 day period in the GFS. Both models show that, between the cut-off low and the tropical system, widespread 1-2″+ rainfall totals are possible throughout the Mid-Atlantic and northern Southeast during the 6-10 day peroid.

NOTE that the GFS 00Z images below are very bullish. Images are courtesy of MDA/EarthSat.

GFS 6-10 day precip totals:

GFS 11-15 day precip totals:

Current drought conditions:

Shots of cool air bringing early fall to the Northeast

A series of low pressure systems will dive into the Northeast and Mid-Atlantic from southern Canada over the next two weeks, which will bring cloud cover and rainy weather to the Northeast. Temperatures could warm up to normal levels between systems, but the majority of the time the Northeast will be hit by below normal temperatures, creating an abrupt change from extreme summer heat to cool fall weather. This pattern does not appear to be long-sustained, though, as ridging over the central U.S. could move warmer temperatures into the East going into the last week of September.

Meanwhile, the southern U.S. will get a period of above normal temperatures as the subtropical ridge sits over the region. Summer has been rather relentless down there this year as far as above normal temperatures, and it looks like it will be awhile before they will catch a break.

EDIT: I’ll probably be using a different U.S. map in the future… I was just trying this one out. The blue on the ocean may be a bit too distracting to the rest of the image.