Browse Month

September 2010

Shipping up to Boston

I’ll be traveling to Boston this morning for the weekend, so I probably won’t be making any updates. Hopefully Jason can get on here and make a post or two…

I think I’m going to need a boat for this instead.

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)

What to Watch Fore(cast) – Sep 27 – Oct 3

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Highlights:

Hot and dry in the West – Very warm temperatures during the work week will provide some areas with record-breaking heat from the West Coast to the Rockies.

Wet week with flooding in the East – As the eastern U.S. gets pummeled by rain early this week, another round of heavy rain is expected during the second half of the work week.

Cool-down in the East – This weekend will be the beginning of a cool period in the East, with several days or more of below normal temperatures on the way.

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Discussion:

A large upper-level ridge produced record-breaking heat in the West, and above normal temperatures will continue through the weekend. Some places in California hit their all-time highest temperatures today, producing numbers in the 108F-115F range. The worst of the heat is over along the Southwest Coast, but double-digit temperature anomalies are still in store for much of the west.

After a moderate dose of rain in the Mid-Atlantic and a good soaking in most of the Southeast, a short break in the rain will give way to another batch of moisture as a subtropical system converges with a stationary front that is just off the East Coast. This rainfall will retrograde back into the East Coast, missing parts of the southeast while providing moderate to heavy rainfalls in the Mid-Atlantic and Northeast. Another 1-3+ inches of rain could come from this next system.

An area of high pressure will move into the Midwest and Southeast over the weekend, which will bring a reinforcing shot of cool air into the East. This could produce several days of temperatures 5-10 degrees below normal in the Midwest and Southeast, with -3 to -5 temperature departures in the Mid-Atlantic and Northeast. The core of the cold will extend from this weekend into mid-week next week.

Mid-Atlantic Discussion – September 27-28

Monday

Strong, twisting winds aloft ahead of a cold front will be the big player as the cold front approaches the Mid-Atlantic Monday and pushes through on Tuesday (from the SE no less!). Weak to moderate thermal instability on the order of 250-750 J/kg CAPE will provide the additional fuel to initiate storms. The strongest threat for severe storms is in CeVA/WeVA as helicity values max out in this area, which creates the greatest twisting motion needed for tornadic development. The upper-level jet is not in the most favorable position for storm initiation, but it could aid in sustaining long-lived cells.

Once these storms get going on Monday, they have the potential to continue well into the evening and overnight hours so long as the CAPE holds out ahead of the storms. Because of the initiation zone and potential life span with these storms, the threat for severe weather could extend NE/NNE following the storm motion into NoVA and MD. The northern extent of best CAPE values does not extend much further N than D.C., so the mesoscale evolution in this region will have to be closely monitored throughout the day for local severe weather potential.

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Chase potential: 85%

Chase target(s):
SoVA/CeVA
NoVA/MD

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Tuesday

The severe threat pushes north and east as we head into Tuesday. The chance for severe thunderstorms will diminish quickly in the region as the cold front pushes through the area, taking the good helicity values with it. Remnants from Monday and/or quick initiation Tuesday morning could spring up severe cells along the Coast. The HPC has the surface front progged to be just east of BWI in a N-S orientation at 12Z, so the front may be moving too quickly for severe storms to initiate locally on Tuesday. Other than that, the synoptic setup is the virtually the same. The upper-level support will be marginally better in NJ Tuesday compared to SoVA/CeVA on Monday, but lower-level speed and directional shear will not be quite as robust.

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Chase potential: 15%

Chase target(s):
DELMARVA/NJ

Parts of the Mid-Atlantic shatter heat records

Some high temperature records were shattered yesterday across the Mid-Atlantic. Here’s the rundown for the D.C. area’s high temperatures:

FORMAT: Station, high, (old high, year of old high)

Yesterday 9/24:
DCA: 99F (94F, 1970)
IAD: 97F (92F, 1970)
BWI: 95F (95F, 1970)

Other major cities that saw record highs yesterday, in City: New (Old) format:
Syracuse, NY: 90F (88F) … Binghamton, NY: 88F (84F) … Atlantic City, NJ: 93F (89F) … Wilmington, DE: 92F (91F) … Richmond, VA: 96F (95F) … Norfolk, VA: 96F (90F) … Wallops Island, VA: 90F (87F)

Today, IAD hit 93F and broke the old record of 92F from 1970. DCA also hit 93F, while BWI came in at 91F. Today also marks the 67th day of 90+ high temperatures at DCA in 2010, which ties the old record set in 1980. DCA’s average high this time of year is 77F.

22 September 2010 Storm Pictures

Went to a local parking garage with Jason yesterday and snapped these two shots (one shown).

Later, another storm formed at dusk and I grabbed this photo from my window:

The second storm eventually hit severe status and was cranking out lightning at a rate of one flash/bolt every 2-4 seconds. Unfortunately, it was just a little too far south for me to grab lightning shots.