MATTNOYES.NET - Weather Website & Blog

TWO BEAUTIES UNDERWAY

Not much to sink our teeth into the next two days in the immediate term.  Best I can offer you is that mixing extends to 850 mb which means good adiabatic warming, but the winds kicked up this morning and temperatures virtually leveled off once the atmosphere became mixed, so temps have virtually plateaued, especially with ongoing cold and dry advection on the active north-northwest wind.  Winds blowing at 25-30 kts at 900 mb have been mixing down from time to time as gusts to between 20 and 30 mph, but these winds weaken during the afternoon.  Surface ridge moves overhead tonight and this means nearly calm wind for most of New England with clear skies and dewpoints in the 30s and 40s.  Lows in the 40s will be common outside of our metropolitan areas and 30s are likely in deeper, sheltered northern and western valleys.  Quick rebound with sunshine and dry air tomorrow, and while mixing isn't quite as deep, warmth is more impressive.  The limit to mixing occurs because of the light wind, but with the high centered south of New England, we should get enough of a weak southwest wind going to induce mixing with 925 mb temps supporting middle 80s!  So, I bumped temps up to meet these numbers, which was not matched by the NMM MOS, but was indicated in GFS MOS guidance.

For the weekend, the thinking has changed little since my discussion two days ago, but having said that, there's still plenty of uncertainty and challenges at work.  While the guess I took on ridge position based on the majority of the guidance products appears as though it will verify, there's still the issue of exactly where to place the pesky weekend frontal boundary, and how to handle timing and intensity of a wave traveling along it.  I have a bitter taste in my mouth from a week and a half ago (roughly, I think) where a surface wave to our south ended up socking up with drizzle for two days straight, and would like to step up to the challenge and get this one dead on.  Desire is nice, but execution is key, and right now my thinking is that the approach of the cold front this Saturday induces a southwest wind on a pressure gradient ahead of it that transports humidity into New England with dewpoints in the 60s to near 70 Saturday afternoon and developing thunder from west to east Saturday late afternoon, evening and night.  A wave of low pressure develops along the front and moves south of New England in response to a shortwave moving overhead Saturday night, and this induces an easterly flow.  Good agreement on a pretty weak wave with little extent on its northwest side, basically meaning the winds will shift during the day on Sunday.  The early onshore flow, however, should mean stubborn clouds in Eastern areas, and in Maine, cool, moist boundary layer advection (in a very shallow boundary layer) may provide lots of clouds and cool air on Sunday (Dad's Day!) while central and western New England find sunshine and 80s, and the rest of eastern areas see emerging sun after the stubborn clouds.  This forecast is tenuous, because it depends upon when/if wind direction shifts.

The same frontal boundary isn't in a hurry to go anywhere, and plays host to another wave on Monday, which may have another quick transition of warm then cold advection, so I carry scattered storms into the forecast as a result.

Matt

AFTER SEVERE WEATHER TODAY, COOLER AIR ENTERS IN INSTALLMENTS

The severe weather threat continues this afternoon, with upward vertical motion increasing ahead of the potent shortwave trough that's digging across the Northeast.  With all of the heat and humidity in place, this will continue to spark severe thunderstorms.  Some storms fired along a boundary that I expected to be more active - one that extends from interior Eastern MA through NH and into ME - though it's been mostly the northern half of this boundary that has stayed active as of this writing.  Winds are light on the southern side of the boundary for several thousand feet into the atmosphere and this hampered evacuation of air aloft, meaning the few storms that developed pulsed then died.  Having said that, the cap (inversion) will weaken in the coming hours, and ascent of air will increase...with tons of heat and humidity still in place...so I believe Eastern MA/Southern NH rides a very fine line between thunderstorm initiation or not, and if anything breaks the cap, it will grow quickly in an environment that features backed winds on the east side of the boundary, yielding the potential for rotating storms if we get storms to pop.  Multiple lines of storms will continue developing out of New York State in the meantime.

Second front Wed afternoon brings chance of thunder to North Country with vorticity maximum riding the border, but rest of New England should stay dry with fair weather clouds amidst dewpoints closer to 60 - feeling a lot drier to the body.  The next front brings drier air, still, and that means great stuff for Thu and Fri.  The weekend brings a challenge of timing of precipitation that's dependent upon the ridge axis and where it sets up - the GFS looked to be a slow outlier and I leaned toward the Canadian Ensemble/Operational Canadian/ECMWF solution of a Saturday evening ridge axis over Eastern ME, which means the rest of New England finds increased humidity and an increased chance of thunderstorms.

Quick updated today due to severe weather coverage.  Thanks for checking in!

COOL NORTHEAST FLOW TO BE REPLACED BY WARMTH, HUMIDITY AND THUNDER

The forecasting challenges continue with issues of inversions, convection and advection leading the difficulty ratings.

Cool air continues to invade the boundary layer on a persistent northeast flow that was enhanced by the low winding up south of New England last night and reinforced by the high drifting south over Eastern Canada and Maine.  The gradient weakens, the high shifts off the coast and the wind changes direction tonight and tomorrow, and this sets warm advection into gear for New England.  At the same time that warm advection kicks in Thursday night and heights build into the the northeast with the expanding ridge, a shortwave currently producing the thunderstorm complex over the Central Great Lakes moves east and brings rain and thunder into New England late Thursday night into Friday morning.  This comes from the combination of dynamic forcing with isentropic lift across the region, assisted by speed and directional convergence associated with an 850 mb jet poking across Upstate NY at 30-40 kts.  This will lead to convective development over Northern and Eastern NY but the mid-level mean flow is from NW to SE, and this means a SE propagation of the showers and thunder, making VT/NH/Ern MA and Southern ME the wettest locales early Friday morning.  Again, this is associated with the combination of a shortwave and warm advection, so as the shortwave moves by and dynamic lift weakens, so too will go the bulk of the precipitation, but the continuing warm advection will combine with some subsidence in the anticyclonic vorticity advection to allow for decent warming where the sun comes out.  925 mb temps would mix out to either side of 80 with the exception of ME where clouds are likely to be more stubborn thanks to the heart of the cool air with the surface ridge being so slow to depart.  A reinforcing shot of boundary layer warmth and moisture will push out of NY and into Western New England Friday afternoon and evening, and scattered severe convective cells would be possible with this warm frontal push.

Though convective activity would die Friday night, warm advection continues.  The ridge builds in for Saturday, but is vulnerable to height falls on its northern periphery thanks to the active northern stream.  With 850 temps supporting mid 90s and 925 temps supporting upper 80s, plus a downsloping flow, seems like 90s are a good bet for many areas both weekend days.  The shortwaves in the northern stream that miss to the north still provide enough lift in a very unstable environment - on the order of 3000+ J/kg of CAPE - to instigate thunder and potentially severe thunder on Saturday, especially in Northern and Western New England, nearest to the dynamic lift.  By Sunday, a better chance of thunderstorms will exist for more of New England with the passage of a surface trough with a shortwave moving across the Canadian border, but dragging the trough across most of New England.  The continued barrage of norther stream shortwaves seems to encourage southward drift of a cold front on Monday, and though most areas will still be in the warm air, showers and thunder would become more numerous.

Matt

THE BRUTE FINESSE OF TORNADOES

There's no question nature can be perplexing, mystifying and awe-inspiring...sometimes all at once.  This interesting piece I came across on MSNBC takes a look at the delicate nature of destruction some of the recent Midwest tornadoes have exhibited.

HURRICANE FORECASTS: FRIEND, FOE, OR JUST GUIDANCE?

(Photo courtesy of Gerry Broome, AP)  Perhaps one of the most exciting, anticipated, and then questioned forecasts in the world of meteorology is the seasonal hurricane forecast.  One of the first to publicize seasonal hurricane forecasts was Dr. William Gray, at Colorado State University, who became known as "The Hurricane Doctor," as his predictions often have been quite accurate.  There have been years that have not verified well, and since Dr. Gray began his forecast several years ago, the National Oceanic and Atmospheric Administration began seasonal hurricane forecasts as a government entity, and many private companies jumped on-board, as well.  Unfortunately, this had given the false perception for the general public that seasonal forecasts were always going to be fairly accurate when, like any forecast, they should be taken as guidance and not used verbatim.  This was a difficult lesson learned in 2006 - following the most active tropical Atlantic season in recorded history - by a number of insurance companies who bought completely into a forecast for an active season, and took high stakes gambles on the forecasts that resulted in bankruptcy.

A couple of articles have come out as of late, pertaining to hurricane forecasts:

National Geographic News takes a look at the updated forecast from Colorado State University - Dr. Gray and his relatively new partner, Bridgewater State College graduate Phil Klotzbach.  Of course, the Associated Press reminds us not to put too much stock in the seasonal hurricane forecasts, and actually does a pretty fair job of explaining that such forecasts are not intended to be the gospel of weather. 

CHALLENGING FORECAST AS WE SLIDE INTO MIDWEEK...POCKET OF DANGEROUS WEATHER POSSIBLE IN MID-ATLANTIC WEDNESDAY AFTERNOON

My apologies for a skipped post yesterday...the craziness continues.  Thanks for checking back in today.

First of all - check out some of the best tornado video I've seen in a long time.  It's posted by Josh Darr on the Midwest Weather Page of NationalWeatherOnline.com - there are three tornado video links there and the second of the three is the best.  From the 24 hour video surveillance camera at a bank destroyed by one of the Kansas tornadoes - awesome stuff.

So there are a few ways to look at our weather pattern evolution in the coming days, but those of you who read often know I usually like to start with the big picture, which in this case features an upper low over the Aleutian Islands, another north of Hudson Bay, and a mid-level ridge over Western Canada with a split Pacific flow racing off the Eastern Pacific Ocean.  This instantly sets up a scenario by which southern stream energy is going to head over the top of a broad South-Central U.S. ridge, instigating MCS action (mesoscale convective systems - organized convection), which we've seen already.  At the same time, the active northern stream shortwaves tug cool Canadian air southward, and rogue anticyclones thrust southward in confluent flow are able to exert influence and increase baroclinicity through the nation's Northern Tier.  This increased baroclinicity leads to frontogenesis, further fueling MCS's and setting up favorable conditions for strengthening low pressure.  The low pressure wave in question is moving through Illinois and has bred an impressive bow echo responsible for widespread damage and wind gusts over 70 mph, with funnel clouds spotted in association with the bookend vorticies on either side of the bow - a remarkable structure, for sure.  As impressive as it is, it's developing in a moisture rich low level environment, fueled by the strong low level jet out of the Gulf of Mexico, and the speed/directional convergence that results.  The guidance has been harping on this low cranking out one to two inches of rain for New England for quite some time, but there are a few reasons I didn't bite on this, with the biggest coming at 500 mb - quick and relatively flat flow.  For as good as the guidance is, last week it suffered convective feedback in a similar situation, and I was suspect that both the NMM, GFS and GEM (Canadian) were all suffering convective feedback issues again this time around.  I think this was somewhat true for New England, and is why new QPF amounts are generally agreed at .10-.25" - some tenth of what the guidance was preaching yesterday and even in today's 00Z runs!  Of course, the 500 mb flow being flat couldn't be the only synoptic reasoning for not forecasting a lot of rain for New England, because the flow is equally flat where they're getting pummeled by thunderstorms.  The difference is that we never really get into the deep positive theta-e advection that's taking place in the Midwest, which means we never get that critical ingredient of isentropic lift enhancement into New England.  Who does get this is from the Southern Tier of NY across Long Island and Northern NJ, where the heavy rain should verify.  I also think the timing is quicker than indicated on successive model runs, but all in all I have to say that I was fairly happy with the 12Z consensus between NMM and GFS and I think they have a much better handle on the situation.  The rainfall amounts still appear somewhat overdone in Northern New England, where the cold front stalling across Central and Southern New England will provide for some isentropic lift into the cool northern air, but probably not as much as the guidance is giving credit for.

Here in New England, the result will be a southward suppressed and less defined surface wave of low pressure (which I still think the guidance is giving too much credit for) which means the cold front/warm front merger (cold front out of Canada, weak mesoscale-type warm front in advance of the low) won't really take place, and instead a SE wind early will give way to a variable wind for most.  Breaks of sun seem like a possibility in CT and SW New England, where temps would respond by jumping into the 70s, while most of the remainder of the area should average upper 60s to around 70, but even cooler in the North Country.  Meanwhile, Southeast PA to Southern NJ (Philly/ACY area) look favorably setup for a severe weather event with excellent potential for rotating supercells and pockets of instability with CAPE to 2000 J/kg or more, and this setup of a tight warm front just north of that region with the surface low to the northwest is a precarious spot to be in - wouldn't be shocked to find an afternoon tornado watch Wednesday for that area with a few funnel reports and perhaps even a touchdown if 0-1 km EHI can crank high enough.  That energy develops a strengthening sfc low south of New England Wednesday night into Thu, but once again I think the models are suffering convective feedback, and while a northeast draining flow may begin the day with clouds and/or fog/drizzle in especially SE New England, I don't think the northeast wind will be as strong or as expansive as is advertised, so I'm planning on improvement during the day Thu, but still not a rapid rebound of warmth.  Ridging builds overhead Thu evening and night, and then the warmth slingshots in for Fri and Sat.  No holds barred on the temps as far as I'm concerned with upstream airmass producing highs in the 80s and 90s, and I've followed suit on the forecast for Fri and Sat, respectively.  Also think the ridge holds on enuf to keep thunder out of the forecast for most on Saturday, tho far Western/Northern New England may be able to weaken the cap enuf for an isolated storm.

That's all for today!
Matt

HURRICANES TO DRIVE GAS PRICES HIGHER?

Though I believe there's a great deal of alarmism that plays into such reports and predictions, the talk has fired up again that an active hurricane season in 2008 could drive already record-high gasoline prices even higher, specifically if cyclones affect the drilling platforms.  To me, perhaps the most bothersome part of this equation is the emotional state of the oil market - the mere entrance to hurricane season...without any storm in the Gulf...has already driven prices up, and that trend is expected to continue.  In fact, it's rather remarkable to see in the past couple of seasons the way oil prices and futures respond instantly to new revisions of forecasts from the National Hurricane Center - a move toward the Gulf, even if forecasted incorrectly, jacks prices up.  Click here to read the article on 2008 gas price dependency on the hurricane season from CNN.com.