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"Big Heat" is here


tombo82685

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The Wxsim module has NW Chesco peaking at 97 on Friday (with highs as follow)

Monday 89

Tues 90

Wed 92

Thurs 94

Fri 97

Sat 95

We have only hit 90 - 3 times so far this year. That 97 on Friday would be the highest I have ever recorded at this location (since 2004) Highest so far for my station is 95.7 on July 6, 2010

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lol u can't look at each model run and say "heat cancel" or like many people do during the winter when they say "storm cancel"...It's the pattern. The GFS did drop a 2 day trough after 240 in the long range but how many times has it been right? Very rarely. Besides that, it has a cool bias. This pattern, a very hot one, is well teleconnected.100+ is rare, so I wouldn't surprised if we don't get that threshold but 95-98 looks like a good bet for at least 3 days.Plus low 90's rest of period.

where did anybody say heat cancel? comment was specifically addressing an individual model run that indicated a significant change from the previous run and nothing to do with any pattern assessment

Philadelphia has recorded 100 or better on 59 occasions so an AVE of once every 2.3 yrs is hardly rare

FWIW 12Z GFS held serve so we'll see how it plays out Sparky

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Ok, so I thought the heat would end on Sunday, but does anyone have any idea what is forcing the full latitude trough in the models next week? The only thing I can figure is the big mountain torque event at the end of last week, but that was over the Himalayas, not the Rockies.

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NWS forecast highs / Maximum heat index forecast for PHL from HPC:

yikes.png

Wed 7/20: 92 / 97

Thur 7/21: 96 / 109

Fri 7/22: 100 / 112, with 36% chance of exceeding 115

Sat 7/23: 97 / 108

Sun 7/24: 98 / 106

See http://www.hpc.ncep....itable_PHL.html

Also check out national map at http://www.hpc.ncep....index_MAX.shtml

Anyone have maximum heat index values from 7/6/10 and 7/7/10 for comparison? Since dewpoints didn't get above 70 in that heat wave I don't think we got over 105 for the heat index at any point, but I could be wrong.

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One thing to remember is that air with more moisture doesn't heat up as fast as dry air. So last year when we went 2 or 3 degrees above the forecast high every day is not to be expected this year. Unfortunately it will feel even more oppressive though.

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NWS forecast highs / Maximum heat index forecast for PHL from HPC:

yikes.png

Wed 7/20: 92 / 97

Thur 7/21: 96 / 109

Fri 7/22: 100 / 112, with 36% chance of exceeding 115

Sat 7/23: 97 / 108

Sun 7/24: 98 / 106

See http://www.hpc.ncep....itable_PHL.html

Also check out national map at http://www.hpc.ncep....index_MAX.shtml

Anyone have maximum heat index values from 7/6/10 and 7/7/10 for comparison? Since dewpoints didn't get above 70 in that heat wave I don't think we got over 105 for the heat index at any point, but I could be wrong.

Wow, didn't even know maps like that existed. Thanks for the links.

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One thing to remember is that air with more moisture doesn't heat up as fast as dry air. So last year when we went 2 or 3 degrees above the forecast high every day is not to be expected this year. Unfortunately it will feel even more oppressive though.

Again, I think that will depend on whether this evening's rain pans out. I think we're already dry enough to see minimal effect from ground moisture.

If the rain fails to materialize and we have another 3 days of sun baking the ground, the stage is set for triple digit highs in many places.

I know IMBY, I've been matching PHL highs almost to the degree the last several days. I'm typically several lower. Yesterday, 89.6 for me, PHL 90.

PHL has had 3 times the rainfall this month that I've had. .48" vs. 1.51"

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Mt.Holly

Sill going with mid 90's on Saturday and low 90's Sunday and Monday for my area.

THE 00Z AND 12Z GFS (AND NOW THE 12Z ECMWF AND UKMET JOINING) ARE SHOWING SIGNS OF LOWER TEMPS AND POSSIBLY LOWER DEW POINTS ON THE WEEKEND. A WEAK BACKDOOR COLD FRONT IS FORECAST TO MOVE INTO OUR CWA ON SATURDAY AND STALL. THIS MIGHT HELP BE THE FOCUS FOR MORE ISOLATED DIURNALLY DRIVEN THUNDERSTORMS. IT ALSO SHOULD BRING SLIGHT RELIEF AS PER THE ECMWF AND GREATER RELIEF PER THE GFS. GIVEN THE STRENGTH OF THE 500MB RIDGE, WE ARE GOING TO SIDE TOWARD THE ECMWF ON THIS. SO WHILE SATURDAY SHOULD BE IN QUOTES COOLER, ITS BECAUSE THE BAR WILL BE SET VERY HIGH ON FRIDAY. THE FRONT SHOULD START BACKING TOWARD THE NORTHEAST ON SUNDAY AND ANY RELATIVE RELIEF WITH RESPECT TO TEMPERATURES AND DEW POINTS SHOULD EB CONFINED TO NORTHERN AND EASTERN PARTS OF OUR CWA. ONCE AGAIN BECAUSE OF THE FRONT`S PROXIMITY WE KEPT IN SOME DIURNALLY DRIVEN CONVECTION.

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0z Euro backs off a tad on Friday -- generally 95-100 for everyone locally (as well as Thursday)...a notch cooler for Saturday but still 95ish for PHL.

Not too gung ho (at this point) on 100 @ PHL...I don't think it really matters since it's going to be a steambath with humidity...

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We are going to fry Thurs-Sat. It is beyond bone dry in my area.......that will help aid the heat. I guess the only plus side is that the humidity shouldn't be as bad as it would be if we had had some decent rain over the past couple weeks. I'm thinking ILG sees 103 on Friday....maybe 104.

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We are going to fry Thurs-Sat. It is beyond bone dry in my area.......that will help aid the heat. I guess the only plus side is that the humidity shouldn't be as bad as it would be if we had had some decent rain over the past couple weeks. I'm thinking ILG sees 103 on Friday....maybe 104.

I doubt that ilg will go above 100 on Friday, however where ilg is located (new castle) is along with the city the warmest spot in delaware.

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We are going to fry Thurs-Sat. It is beyond bone dry in my area.......that will help aid the heat. I guess the only plus side is that the humidity shouldn't be as bad as it would be if we had had some decent rain over the past couple weeks. I'm thinking ILG sees 103 on Friday....maybe 104.

A met can correct me if I'm wrong, but from what I understand soil moisture has only a limited effect on humidity. The amount of evapotranspiration of soil moisture can produce slight increases in the dewpoint, most notable when looking at overnight lows, but we can still have a humid airmass with dry soil. As of 10:54am, DPs across PHL's CWA range from 67-72, despite very dry soil in most places. Last July, our heat wave featured DPs in the 40s, maybe cracking 50 at one point. While there was less rainfall last summer, that does not account for a 20-25 degree difference in dewpoint between the two events.

In other words, what I'm saying is it will still be just as humid as it was forecast to be 3 days ago, even without last night's rain. I think....

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If this heat is going to last for several days, I want it to be topping 100. Here's hoping we do it.

Personally, I hope it doesn't. It's not like we haven't had record heat for a while. Chances of beating last year's temps are slim. It will feel bad either way, though. Maybe the Euro is right - we'll see what the 12z Euro says.

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