A heat wave recap; generally quiet tropics

By: Dr. Jeff Masters , 4:45 PM GMT on July 25, 2011

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Last week's U.S. heat wave has finally subsided, and most of the Northeast will see some cool highs in the 70s today. Unfortunately, the Midwest, and mid-Atlantic will continue to see high temperatures in the 90s for the rest of this week, and the southern Plains will be forced to continue to endure triple-digits.

According to the National Climatic Data Center (NCDC), 2,100 daily high maximum temperature records have been set so far in July 2011, and 51% of those were set last week. 4,734 daily high minimum temperature records have been set so far this month, and 55% of those were set last week. Here's a breakdown of last week's records for the period July 18 through July 24:

High Maximum:

• 1,076 warmest maximum temperature for the date
• 90 warmest maximum temperature for the month of July
• 56 warmest maximum temperature of all time

High Minimum:

• 2,595 warmest minimum temperature for the date
• 207 warmest minimum temperature for the month of July
• 123 warmest minimum temperature of all time

The number of warm minimum temperatures is especially disturbing, as these tend to have more of an impact on health than the high maximums. When the temperature remains high at night, it prevents the body from being able to recover from the day's heat. According to NOAA, from July 1 through July 19, there were 22 heat-related deaths in the United States. Reuters is reporting that 34 deaths resulted from this heat wave. In an average year, heat remains the number one weather-related killer in this country. In some ways, the overnight low temperatures are the best way to quantify a heat wave, possibly even better than the heat index.


Figure 1. Map of daily high maximum temperature records for the period July 1 through July 25 from NCDC. Red circles without an X denote a broken record; red circles with an X denote a tied record.

Tropical Overview

The wave formerly known as Invest 90L

The wave formerly known as Invest 90L is moving slowly west through the Caribbean near Jamaica. A new burst of convection started this morning, which will undoubtedly produce some heavy rain over southern Cuba and Jamaica. While low-level circulation has remained about the same since late last week, the wave has become top-heavy with increased circulation at higher levels (700-500mb). None of the models (GFS, ECMWF, CMC, NGPS, UKMET) are developing this wave as tracks into the Gulf of Mexico, and they're all in agreement that the path will be toward far southern Texas or northern Mexico, except for the ECMWF deterministic run, which hints that it will take a turn toward the northern Gulf. However, this model hasn't shown actual development from the wave since Tuesday or Wednesday of last week.

NHC has dropped this invest as of Saturday afternoon, but it remains on their radar. They're giving the wave a 0% chance to form over the next 48 hours. Given the recent uptick in mid-level circulation, I'd imagine they're still a little concerned about the potential for this wave to fire-up again once it's in the Gulf, and it will surely be of concern for Cuba as it tracks westward. However, given the lack of model support for almost 7 days in a row now, I'd say this wave has seen its glory come and go.


Figure 2. Visible tropical Atlantic satellite captured at 11:14am EDT on Monday.

Other North Atlantic waves

There are a couple other waves to speak of that have left the coast of Africa in the past few days, one located near 40W and the other closer to Africa, around 30W, which is tangled up in the monsoon trough. The former is expected to take a southerly track, skirting northern South America, and possibly into the Bay of Campeche. Given this track, none of the models are suggesting it will develop. However, tropical cyclones that spin up in the Bay of Campeche generally have a short forecast lead time, so it's something to watch. The latter wave could take a slightly more northern track through the Caribbean islands, and a couple of the models seem to favor this wave for development at the end of their runs.

Tropical wave activity has been lacking so far this season, but climatologically we should see an increase in African easterly waves in August and September.

Angela

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Tex/Mex Friday & Saturday, TS or low 1. We could use it but just the TS. My take, not a Met.
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GOES East is in RSO mode, so increased number of images per hour from a GHCC Loop X 90L
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Quoting islander101010:
you all on that little spec on this vis.


I just updated my blackberry GPS, I'm on the SW side of Grand Cayman(South Sound) coordinates are 19.16N/81.23W
Member Since: April 29, 2007 Posts: 0 Comments: 7832
Gotta get back to work. Later all.
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Will be interesting to see how ex-90L handles d-min tonight.
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I am guessing Dr Masters is going with hired hands rather than a "featured blogger" to avoid the lovely mishaps of years past...
Good idea and great post Angela
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Quoting stormpetrol:
I actually think whatever circulation there is around 18/78


The water vapor loop seems to rorate around that area...
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Quoting islander101010:
i heard if you hear super loud one thats a sign something going on


this was one of those ones where you just hear it you dont see the flash so it was pretty close lol
Member Since: October 21, 2009 Posts: 0 Comments: 355
Why that significant wave hight on July 31st?

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Quoting stormpetrol:


I think you're right , I was suspicious of that myself, the highest I've seen here in South Sound is about 20-25mph, could been a waterspout crossing by the airport!


Absolutely could have been a waterspout could have been the distubance i saw tearin up the trees....it was heading towards the airport as you know red bay is just ese of there
Member Since: October 21, 2009 Posts: 0 Comments: 355
Quoting Saltydogbwi1:


cell tower right next to my house got hit by lightning about 15 mins ago damn that was LOUD! well i think thats what it hit cause right after it happened the singnal on my phone dropped to 1 bar from 5
i heard if you hear super loud one thats a sign something going on
Member Since: September 11, 2010 Posts: 1 Comments: 4512
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Take care in judging how much mid-level circulation is evident on satellite imagery. WSW shear of the cloud tops on the southwestern side of ex-90L is giving the illusion of more circulation than there actually is. There is some, though.
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Quoting weatherh98:


which is better for development


850
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489. xcool





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Quoting islander101010:
stormpetrol & local characters keep us informed
you all on that little spec on this vis.
Member Since: September 11, 2010 Posts: 1 Comments: 4512
486. xcool
20% at 800pm
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Quoting islander101010:
stormpetrol & local characters keep us informed


cell tower right next to my house got hit by lightning about 15 mins ago damn that was LOUD! well i think thats what it hit cause right after it happened the singnal on my phone dropped to 1 bar from 5
Member Since: October 21, 2009 Posts: 0 Comments: 355
Quoting stormpetrol:
Link
1011mb.....nice.
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90L seems to be setting up to be a best case scenario for drought plagued Texas.
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Quoting alfabob:

What is the link for the mb version of the graph? I'm using the NDBC site but it is in inches and isn't updating.


Change units to metric from the drop-down menu at the top of the obs.
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Quoting Saltydogbwi1:


Hey petrol, although its not impossible with these thunderstorms I doubt thats a true reading I was working on a boat about an hour ago down in red bay and a small dust devil/twister had formed it twisted the top of the trees up a bunch and took leaves and debri high into the air but then dissapeared...having said that that particular station seems to give a lot of false readings I saw wind gusts last year as high as 80 mph on it I believe it gets affected by the Jetwash from the aircraft engines as it is at the airport.


I think you're right , I was suspicious of that myself, the highest I've seen here in South Sound is about 20-25mph, could been a waterspout crossing by the airport!
Member Since: April 29, 2007 Posts: 0 Comments: 7832
Very obvious mid-level turning on visible imagery now NE of the Cayman islands in the area of strongest vorticity...
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Thanks Angela!
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stormpetrol & local characters keep us informed
Member Since: September 11, 2010 Posts: 1 Comments: 4512
What's going on?



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Dvorak Current Intensity Chart

Link
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Link
Member Since: April 29, 2007 Posts: 0 Comments: 7832
Quoting stormpetrol:
Link

According this within the last hour we had a wind gust of 60mph at Owen Roberts Airport, Grand Cayman


Hey petrol, although its not impossible with these thunderstorms I doubt thats a true reading I was working on a boat about an hour ago down in red bay and a small dust devil/twister had formed it twisted the top of the trees up a bunch and took leaves and debri high into the air but then dissapeared...having said that that particular station seems to give a lot of false readings I saw wind gusts last year as high as 80 mph on it I believe it gets affected by the Jetwash from the aircraft engines as it is at the airport.
Member Since: October 21, 2009 Posts: 0 Comments: 355
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On the plus side for ex-90L, pressures at Grand Cayman are down to 1012mb, 2mb lower than at 12z this morning. Pressures are also falling in the NW Caribbean well ahead of the wave, meaning that the pressure falls at this buoy are not associated with the tropical wave, but rather with a large-scale air mass loss in the region, indicating an improving environment ahead of the wave.

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I actually think whatever circulation there is around 18/78
Member Since: April 29, 2007 Posts: 0 Comments: 7832
Quoting weatherh98:


which is better for development


Better would be having a well-defined low-level circulation that has to work upwards (850mb vorticity being stronger). Best would be having well-defined vorticity at both levels.
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Well at this point I will not say that 90L is gone, although I think the NHC will rename it to 91 or 92L by the time it goes into the Gulf


Taco :o)
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See the long tail holding stationary off of 90L...it's feeding itself
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Link

According this within the last hour we had a wind gust of 60mph at Owen Roberts Airport, Grand Cayman
Member Since: April 29, 2007 Posts: 0 Comments: 7832
Look at that satellite image Angela posted. Impressive extratropical storm just east of Newfoundland.
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Quoting Levi32:
The wave is definitely more pronounced at 700mb than 850mb:

700mb:



850mb:




which is better for development
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You aint kidding about the glory days at UM... Boy do I miss the UM of the 80's and 90's.
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Quoting lucreto:


90L is gone just like the glory days of UM


You mean scUM right ;)
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The wave is definitely more pronounced at 700mb than 850mb:

700mb:



850mb:


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i wonder if doc has a username and comments on his own blog or convo and we dont know it yet
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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