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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90L looks better now than at any previous moment
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Quoting angelafritz:
Convection around former 90L is looking decent, however, I think any circulation we're seeing is probably still at mid-levels. I don't quite understand what NHC means by "atmospheric conditions are not expected to be conducive." Deep layer shear isn't that high (there's a nice pocket of low shear along the expected path) and even though humidity is low in the Gulf in general, the wave has maintained it's high specific humidity (4 to 5 g/kg) throughout its lifetime, which is expected to stay with the wave as it crosses the Gulf. I think the kicker here is that mid-level vort is not translating to the surface.



very good analysis.
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90L is just about stationary, festering imo. 20% at 8pm to say the least!
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Looks like Cloudburst may only be off by a week
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Quoting TxHurricanedude11:

I think it will lol


We'll see, but I have my doubts. If this hits the Yucatan tomorrow it's done.
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Quoting angelafritz:
Convection around former 90L is looking decent, however, I think any circulation we're seeing is probably still at mid-levels. I don't quite understand what NHC means by "atmospheric conditions are not expected to be conducive." Deep layer shear isn't that high (there's a nice pocket of low shear along the expected path) and even though humidity is low in the Gulf in general, the wave has maintained it's high specific humidity (4 to 5 g/kg) throughout its lifetime, which is expected to stay with the wave as it crosses the Gulf. I think the kicker here is that mid-level vort is not translating to the surface.


YET
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Quoting cloudburst2011:
a ull off the coast of belize has developed and this could cause 90L to move more on a nw course and miss the yucatan all together...also 90L the outflow coming from the southwest and northeast is causing some fanning out...90L will be a tropical depression in 36 hours...this could develop rapidly after that with ssts in the gulf near 90degrees..its going to be very interseting the next 36 hours...


You said this would be Don by last Thursday.

This won't be a depression by this Thursday.
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596. angelafritz (Admin)
Convection around former 90L is looking decent, however, I think any circulation we're seeing is probably still at mid-levels. I don't quite understand what NHC means by "atmospheric conditions are not expected to be conducive." Deep layer shear isn't that high (there's a nice pocket of low shear along the expected path) and even though humidity is low in the Gulf in general, the wave has maintained it's high specific humidity (4 to 5 g/kg) throughout its lifetime, which is expected to stay with the wave as it crosses the Gulf. I think the kicker here is that mid-level vort is not translating to the surface.
Quoting BahaHurican:
That twin vortex thing is not helping this wave...
but it looks more interesting
Member Since: September 18, 2010 Posts: 0 Comments: 4570
WOW it's soooo humid outside.Even after when it rained like two times today.It rained really hard the second time around for like 20 minutes.Well at least this is helping with the dry ground outside.
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checked Negril Jamaica winds 7-10 out of the SE, Negril is not in the convection at this time
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Quoting Saltydogbwi1:
is it my eyes or do the lower level clouds in the gulf just NW of the Yucatan change direction in the last few frames of this loop?

Link


Noticed that, too. I think we may have ignition.
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Quoting nrtiwlnvragn:


I did not mean never, you asked if in a few hours. If it can sustain convection overnight around a convective center, then it is possible. However the wave will soon be running into the Yucatan. TAFB has it there by tomorrow morning, I don't think it will be that fast.




Good. I agree about the slowdown in NW Caribbean.Let's see what ATCF does depending of how the system looks.
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850MB vorticity really improved this afternoon.
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From one of Dr. Master's old entries from years back:

Why have so many hurricanes hit the U.S.?

As was the case during the 2004 hurricane season, there has been an unusually stong ridge of high pressure over the East Coast of the United States during most of the 2005 hurricane season. This ridge has steered storms westward across the United States coastline instead of allowing them to recurve out over the open ocean.

The fact that I find concerning, is that this season, we also have an unusually strong ridge of high pressure. I hope everyone is prepared for this season, as it looks to be a bad one.
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Quoting BahaHurican:
@ PRweathercenter.... I hate to do it, but I just put you on my ignore list. This is because every time you post a video it screws up the blog. I don't haven anything against you. I just can't take the screwed up blog....

Anybody else using IE may find that this is a solution to your problem...



There's no problem with folks that have Firefox or Chrome.

Only IE users are reporting the problem as you mentioned.

Try some of the new browsers and there should be no problem.
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I would like to thank you all for your analysis. I've (mostly) lurked for years. I'm finding that watching and listening about potential systems like 90L is more educational than following a developed TC. I feel like I know most of you personally and although I don't feel capable of contributing, maybe this year I'll post questions when I have them. Thanks again.
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I think the actual LLC starting to get going WSW of the western tip Ja. Somewhere around 18/78., actually just a tad south due west of Ja.
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Quoting P451:



On Visibles such as this I am drawn towards the area a few mention (around 20N?) off of Cuba.

On WV such as what I posted I am drawn towards the area off of the western tip of Jamaica.

I circled both regions of interest on the one image and labeled which imagery shows which area of interest best. Both regions have some twisting to them.

x90L certainly became interesting - surface wise - for the first time this afternoon.

turning and convection, lets see what the convection does over several hours
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Quoting lucreto:


And you sir have an MCS look



I don't know what do you mean with an MCS look but I hope is nothing disrespectful.
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Quoting BahaHurican:
@ PRweathercenter.... I hate to do it, but I just put you on my ignore list. This is because every time you post a video it screws up the blog. I don't haven anything against you. I just can't take the screwed up blog....

Anybody else using IE may find that this is a solution to your problem...



windows 7 64bit and 64bitIE9 have no issues at all that i have noticed I dont know what version your using though
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574 looks like a switch from the NE, maybe indicative of a developing LLC beginning where Jamaica is... I don't really know though.
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Quoting Tropicsweatherpr:
nrtiwlnvragn,even if it starts to organize, 90L never will be reactivated?


I did not mean never, you asked if in a few hours. If it can sustain convection overnight around a convective center, then it is possible. However the wave will soon be running into the Yucatan. TAFB has it there by tomorrow morning, I don't think it will be that fast.


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Quoting BahaHurican:
@ PRweathercenter.... I hate to do it, but I just put you on my ignore list. This is because every time you post a video it screws up the blog. I don't haven anything against you. I just can't take the screwed up blog....

Anybody else using IE may find that this is a solution to your problem...



Quoting Tropicsweatherpr:


I did the same.


Or...Instead of ignoring a perfectly good blogger, you could get Google Chrome or Firefox.
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Ex 90l has been nearly stationary since morning, this has helped this wave to reorganize
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Quoting BahaHurican:
@ PRweathercenter.... I hate to do it, but I just put you on my ignore list. This is because every time you post a video it screws up the blog. I don't haven anything against you. I just can't take the screwed up blog....

Anybody else using IE may find that this is a solution to your problem...



I did the same.
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is it my eyes or do the lower level clouds in the gulf just NW of the Yucatan change direction in the last few frames of this loop?

Link
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Quoting RitaEvac:



Things a look a little more speculative for sure.
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@ PRweathercenter.... I hate to do it, but I just put you on my ignore list. This is because every time you post a video it screws up the blog. I don't haven anything against you. I just can't take the screwed up blog....

Anybody else using IE may find that this is a solution to your problem...

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570. beell
TCHP July 24

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nrtiwlnvragn,even if it starts to organize, 90L never will be reactivated?
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That twin vortex thing is not helping this wave...
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High pressure is weak on it's southern edge, note the activity along Louisiana and TX coasts
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Got some light rain at the moment here on Grand Cayman, winds are slight though out of the S-SE
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ex-90L has a cyclonic look !!!!
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Quoting P451:



On Visibles such as this I am drawn towards the area a few mention (around 20N?) off of Cuba.

On WV such as what I posted I am drawn towards the area off of the western tip of Jamaica.

I circled both regions of interest on the one image and labeled which imagery shows which area of interest best. Both regions have some twisting to them.

x90L certainly became interesting - surface wise - for the first time this afternoon.



That same loop on "naked water vapor" looks like a broad low between the Caymans and Jamaica, at least to me. Link
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558. xcool
P451 taker care
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.