WEATHERAmerica Newsletter, Sunday, April 15, 2007 at 3:35 A.M. ET

[Larry_Cosgrove]

Bombogenesis Over New Jersey! Massive Storm Threatens The Northeast With Widespread Flooding From Heavy Rain And Coastal Surges (With High Elevation Blizzard In The Interior); Decidedly Warmer Pattern Follows Severe Weather Episode Across The Deep South Later This Week

(Disclaimer And Copyright Statements At End Of The Discussion)

WEATHER SUMMARY THROUGH NEXT 72 HOURS


Yesterday, someone said to me, "if only this was January" in reference to the huge storm that is unfolding over the Northeast. Problem is, this system could have hit any time in the low sun period and the result would be the same in the major cities of the Interstate 95 corridor: rain. Lots of rain. And little, if any, snow.

The problem for snow lovers (and it should be said, those not wanting widespread flooding) is that the track of this disturbance will not be offshore. As I write this discussion, it is plain to see that the deepest pressure falls are occurring from the juncture of KY and the Virginias, with the path of the low center likely through DE into C NJ before stalling out over Nassau County LI NY. That type of trajectory ensures that warm air will reach as far west as C PA and C NY. With a strong southeast wind flow at surface, weather enthusiasts may be shocked to see the major issue being a coastal surge of up to 6 feet. Thunderstorms may near severe limits from the Chesapeake and Delaware Bay vicinities into the New York NY metro area (I am thinking up to a Newark NJ....Commack LI NY line). And when you factor in overrunning and convective processes working with tropical air from the Gulf of Tehuantepec, you have a recipe for a flooding disaster with 3-6 inches total rain. Since the low will bomb out and get stuck very near "The Big Apple", all of those crazed QPF depictions north of the Potomac River into ME are very likely correct. There will be precipitation, for example, in Paterson NJ through Wednesday morning.

In terms of the coastal surge, it is clear that we can pinpoint a disaster in the making along the shorelines of LI NY (Atlantic facing) and CT, RI, and SE MA. The size of the broad deep pressure gradient will cook up winds of perhaps 60-70 mph for perhaps 12-18 hours in that vicinity before the low starts to fill and spin down, so the "wall of water" scenario is going to put many of the resorts and coastal towns in sea water by tonight. Add also the rains, which will inundate the coastal plain, and you have something akin to a Hollywood disaster movie. Or Weather Channel series, for that matter.

For the snow hounds, you will have to drive into the mountains of N PA....C NY....VT....NH to see the white side of this event. Some locales will have a shot at 2 feet of heavy wet snow; I would not be surprised to see the fringes of ON and S QC get in on the "wet whiteout" tonight. But sunlight, lower elevation and filling of the upper low will lessen the potential for flake formation on Monday and Tuesday. By the time temperatures at 850MB are low enough (-5 C or less) in the major northeastern cities, the moisture will be moving out on Tuesday night.

The cPk penetration behind the giant storm will sweep out the Gulf Coast, making for chilly nocturnal readings through the near term. But the introduction of clear skies and dryness with high sun angle will mean fast warming in Dixie as well as the Midwest. So while the 32 deg F isotherm makes its last southward binge of the season into the Deep South, it is entirely possible that readings approaching 70 F could reach into the Ohio and Missouri Valleys by Day 3.

For our friends across the western states and Great Plains, there is the not insignificant matter of the deep upper trough now passing through the Intermountain Region. If you look carefully at the satellite representation of this feature, you will notice yet another percolation in the subtropical jet stream over the eastern equatorial Pacific Basin. This jet streak will energize the low as it closes off across AZ and NM, creating another opportunity for an important severe weather episode in TX....OK....S KS on Day 3. A rather cool mPk regime will filter in behind the impulse through the western states by Tuesday, starting a trend for chilly conditions in the West that may linger through the medium range.

SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)


ISOLATED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
NC Outer Banks....E VA....E MD....DE....C, S NJ....S LI NY

Some Thunderstorms May APPROACH Severe Limits
FL Peninsula

STRONG WINDS (Pressure Gradient Derived)
NH....VT....MA....RI....CT....NY....NJ....PA....MD ....DC....VA....WV....E KY.....E TN....W NC
SC....GA

COASTAL FLOODING
NJ....NYC and LI NY....CT....RI....SE MA

ISOLATED Severe Thunderstorms
(Large Hail)
C, S CA....S NV....AZ....W NM....W CO....UT



HEAVY RAINFALL OUTLOOK
(potential for an inch or more total rainfall within the next 24 hours)


NUMEROUS Locations In
WV....VA....DC....MD....DE....NJ....PA....NY....CT ....RI....MA....NH....VT
(QPF 1 - 6"; Widespread Flooding)

Isolated Locations In
FL Peninsula....SE GA....E SC....E NC
(QPF 1-3")


WINTER WEATHER OUTLOOK
(potential for 2-4 inches or more of snow, or significant ice/glazing)

NUMEROUS Locations In
N WV....Garrett County MD....W, C PA....W, C NY....VT....NH....QC Eastern Townships
extreme E ON
(Wet Snow; Some Sleet, Rain; Blizzard conditions Above 1000 Feet; 4-24")

MEDIUM RANGE OUTLOOK
(weather trends through the next 6 to 10 days)

Raw, dreary weather will be difficult to shake off in parts of the Great Lakes and Northeast later this week. Even as the gigantic storm currently unfolding over the Northeast starts to wind down, the Rex block retrogressing from QC into MB will force a small disturbance from W ON into the Ohio Valley and Mid-Atlantic states, maintaining a mantle of cool temperatures, cloud cover and showery precipitation. Another factor is the storm complex now taking shape across the western states. This system represents a severe weather threat from the lower Great Plains through the Deep South during Days 3 - 5; if some phasing occurs between the southern branch and the northern, the result could be another raw rainmaker along the Eastern Seaboard. As of now, however, the NWP schemes keep both impulses separate and begin a clearing trend in the Atlantic Coastal Plain around 132 hours.

It seems fairly evident from the computer models and the ensemble members that the 500MB longwave pattern will undergo a shift from an -NAO/Rex block dominated to -PNA configuration by next weekend. This should bring about a very warm pattern (though not hot or record-breaking) east of the Rocky Mountains through much of the Day 6-10 time frame. A trough complex (positively tilted) looks to take shape across the Intermountain Region, with cool readings through most of the West outside of coastal CA, where downslope flow may yield some very mild temperatures. There are hints that a significant severe weather event could unfold in the Great Plains around April 25 as the trough begins to exit the western states, with surface convergence increasing from OK into NE and IA.

Prepared by Meteorologist LARRY COSGROVE on
Sunday, April 15, 2007 at 3:35 A.M. ET

Disclaimer:

The previous statements are my opinions only, and should not be construed as definitive fact. Links provided on this newsletter are not affiliated with WEATHERAmerica and the publisher is not responsible for content posted or associated with those sites.

Copyright 2007 by Larry Cosgrove

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[rainstorm]

we are all looking forward to an end of the flooding and cold. i pray for drought this summer.