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Next Monday-Tues frontal passage


free_man

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It seems like a difficult forecast pinpointing and timing the next several days, that is for sure. However, I'll take the fast w wnw flow aloft all day every day.

...NEW ENGLAND AND VICINITY...

THOUGH DIFFERENCES ARE EVIDENT BETWEEN THE ECMWF AND GFS...GENERAL

AGREEMENT EXISTS THAT THE FRONT CROSSING NEW ENGLAND DURING THE DAY

WILL BE A FOCUS FOR SHOWER/THUNDERSTORM DEVELOPMENT...AS MARGINAL

AFTERNOON DESTABILIZATION OCCURS WITHIN THE PRE-FRONTAL ENVIRONMENT.

MODERATE WLY FLOW ALOFT TO SUPPORT POTENTIAL FOR ORGANIZATION --

WITH LINEAR MODE ANTICIPATED. THUS...DAMAGING WINDS WILL LIKELY BE

THE MAIN SEVERE THREAT -- PRIMARILY DURING THE DIURNALLY FAVORED

AFTERNOON HOURS.

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somewhat interesting set-up for Tuesday.

one thing that gives pause is SNE spends an awful long time in the right exit region of a pretty strong UL jet. doesn't mean nothing can fire off and go but maybe NNE is better positioned?

Coast of Maine is pretty unstable actually.

Some of the parameters are good, especially on the NAM. GFS is a bit faster with the front, but the euro also leaves only a little wiggle room for parts of SNE.

0-6KM Shear about 40-45 kts or so. CAPE looks good on the NAM too with around 2000J ML CAPE (obviously TD dependent here). Good surface to 500mb crossover vectors, especially central and eastern areas.

Some of the downfalls though seem to be lack of decent s/w forcing until evening time. Jet placement is better for Maine as well. Could be one of those things like on June 1st where perhaps something develops during the day, but then we get a nice line forming along the actual cold front, once the good s/w forcing arrives? I've seen questionable setups produce, so it is possible to get something decent (perhaps BOS-HFD?). I noticed the SREFs and NAM like that area just mentioned, but we are pretty far out as well.

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NAM still a little iffy with timing, but looks like it brings convection more with the actual cold front. SREFs still seem to target I-84 region to BOS area it seems. Much better support with the actual front, though.

BUFKIT is actually a little more impressive tomorrow for BAF and ORE. Showing @ or > that 1,000 SBCAPE and brief spike in helicity to 120 around 7pm, at which time llv cap is temporarily desolved - abused by evaporating towers at dusk. I could see an isolate interesting cell or two late tomorrow.

As for Tuesday, it looks like we CINH ahead of the fropa - could just be the one run but the lower troposphere wind at both locations backs wnw and it's over by 1pm... I'm wondering if there's a prefrontal trough that acts like a dry line and then whips out to sea. I have seen impressive set ups get robbed away to anitclimax results because of the idiosyncrasy of New England's home grown "dry line"

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BUFKIT is actually a little more impressive tomorrow for BAF and ORE. Showing @ or > that 1,000 SBCAPE and brief spike in helicity to 120 around 7pm, at which time llv cap is temporarily desolved - abused by evaporating towers at dusk. I could see an isolate interesting cell or two late tomorrow.

As for Tuesday, it looks like we CINH ahead of the fropa - could just be the one run but the lower troposphere wind at both locations backs wnw and it's over by 1pm... I'm wondering if there's a prefrontal trough that acts like a dry line and then whips out to sea. I have seen impressive set ups get robbed away to anitclimax results because of the idiosyncrasy of New England's home grown "dry line"

GFS really dries us out on Tuesday as well. Does show a nice KI surge MOnday night with s/w passage, so perhaps maybe some storms around, but probably won't know until tomorrow.

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I'm not all that concerned about the timing on Tuesday, I think the GFS is a bit fast. Even the NAM which is slower I would think is a bit fast by a few hours. I don't think we'll see much in the way of clud debris on Tuesday, especially down here in CT with the w/nw flow aloft.

I'm more worried about:

1. sfc/BL winds...do they end up being more westerly which would allow for dry air to mix down into the BL and to the sfc mixing out dews limiting instability.

2. Potential cap around 700-600mb...NAM soundings show a fairly strong cap here

3. ML lapse rates look pretty horrible

One thing we can likely agree on right now is we will at least see some torrential rains likely causing some flooding issues, especially in spots hit hard on Friday.

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I'm not all that concerned about the timing on Tuesday, I think the GFS is a bit fast. Even the NAM which is slower I would think is a bit fast by a few hours. I don't think we'll see much in the way of clud debris on Tuesday, especially down here in CT with the w/nw flow aloft.

I'm more worried about:

1. sfc/BL winds...do they end up being more westerly which would allow for dry air to mix down into the BL and to the sfc mixing out dews limiting instability.

2. Potential cap around 700-600mb...NAM soundings show a fairly strong cap here

3. ML lapse rates look pretty horrible

One thing we can likely agree on right now is we will at least see some torrential rains likely causing some flooding issues, especially in spots hit hard on Friday.

GFS may be a little fast, but def some questions Tuesday. I do think something could come through tomorrow night.

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:lol:

It means the 15z SPC SREF virtually gives us little in the way of severe wx threat...probably more of a heavy rain/flash flooding threat.

I don't see how it looks much different than the previous runs. Still similar thunderstorm and severe thunderstorms probs especially from HFD to TAN. The threat diminished for western CT and MA on the latest run though...looks better for eastern areas.

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I don't see how it looks much different than the previous runs. Still similar thunderstorm and severe thunderstorms probs especially from HFD to TAN. The threat diminished for western CT and MA on the latest run though...looks better for eastern areas.

Kind of looks like the probs decreased...especially with the craven sig svr...smaller area of 20000 while past runs had 30000+.

Not sure if you're aware of this but if you click on the individual hour scale a separate page comes up and you can compare past runs to that hour. Here are the severe wx probs for 21z Tuesday from the 15z run and you can compare them to past runs for 21z Tuesday...as you will see it decreaed the svr probs BIG time

http://www.spc.noaa.gov/exper/sref/sref_matrix_hover.php?fhr=f054&startdate=2011071015&field=SREF_03HR_SVR_PROBS__

Here is the craven sig svr probs

http://www.spc.noaa.gov/exper/sref/sref_matrix_hover.php?fhr=f054&startdate=2011071015&field=SREF_CB_MEDIAN_MXMN__

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Kind of looks like the probs decreased...especially with the craven sig svr...smaller area of 20000 while past runs had 30000+.

Not sure if you're aware of this but if you click on the individual hour scale a separate page comes up and you can compare past runs to that hour. Here are the severe wx probs for 21z Tuesday from the 15z run and you can compare them to past runs for 21z Tuesday...as you will see it decreaed the svr probs BIG time

http://www.spc.noaa....3HR_SVR_PROBS__

Here is the craven sig svr probs

http://www.spc.noaa....B_MEDIAN_MXMN__

FROPA is faster...look at 18z. That's when everything peaks.

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Yeah...I'm still not really buying this faster fropa solution. I still think we end up seeing a slower fropa, even slower than what the slowest models are showing...we've seen that happen with the past 3 or 4 of them.

slower FROPA is better...severe weather indices are peaking now at 18z and dropping afterwards. We'd like to see them peaking at 21z or so again IMO. The reason they probably dropped slightly in magnitude this run was because everything didn't fully destabilize before the front came through, still the severe weather parameters are pretty good.

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slower FROPA is better...severe weather indices are peaking now at 18z and dropping afterwards. We'd like to see them peaking at 21z or so again IMO. The reason they probably dropped slightly in magnitude this run was because everything didn't fully destabilize before the front came through, still the severe weather parameters are pretty good.

I really would not be surprised to see a FROPA actually past 0z which would still be great, especially for northern sections. This would certainly allow for sufficient heating/destabilization and shear actually increases even more late in the evening and helicity even spikes a bit.

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