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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wave at 35w is becoming to look interesting. will do a little analysis later.
Member Since: Posts: Comments:
Quoting AllStar17:
This is where I see the most rotation evident:
yup me to. I do see what Rita see's also.
Member Since: September 18, 2010 Posts: 0 Comments: 4969
Quoting Tropicsweatherpr:
nrtiwlnvragn, do you see 90L reactivated in a few hours?


No
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Low level clouds in that area come to a grinding hault SW of tip of Jamaica, which tells me the beginning of a possible LLC is about to form later on

Check visible to see
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Realizing the water vapor loop is not indicative of LLC, I keep looking at that loop and the surrounding moisture environment...and knowing the TCHP ahead I have to think there is a magnificent set-up for this to do a full-Lazarus.
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nrtiwlnvragn, do you see 90L reactivated in a few hours?
Member Since: April 29, 2009 Posts: 75 Comments: 13931
SW from tip of Jamaica...

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Quoting KEEPEROFTHEGATE:
some nice afternoon heat induced thunderstorm activity has dev i see you do know when the sun is gone so are the storms right
xx/xx/xx


Seen this movie before? Played this last Saturday and Sunday.
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546. xcool
P451 ;)
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again my eyes are pulling me towards the area NW of jamaica south of cuba and east of the caymans and as of now convection is wraping around that circulation look at the images
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some nice afternoon heat induced thunderstorm activity has dev i see you do know when the sun is gone so are the storms right
xx/xx/xx
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542. JRRP
ex 90L SAT
Link
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has the drain look
Member Since: September 11, 2010 Posts: 1 Comments: 4268
Quoting JRRP:
12z CMC ensemble




Interesting.. thanks.
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Quoting HurricaneHunterJoe:
to my eyes loks like 2 circulation/vortices, one just west of the western tip of Jamaica and another off the south cuban coast


Max magnification GHCC X 90L
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537. xcool
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Allstar correct, but that's in the mid levels, for some reason I'm being pulled to the SW of the tip of Jamaica, for whatever reason, that area is suspicious
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Quoting nrtiwlnvragn:
GOES East is in RSO mode, so increased number of images per hour from a GHCC Loop X 90L
to my eyes loks like 2 circulation/vortices, one just west of the western tip of Jamaica and another off the south cuban coast
Member Since: September 18, 2010 Posts: 0 Comments: 4969
534. JRRP
12z CMC ensemble


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Whatever rotation we are seeing at the time is in the mid-levels. HOWEVER, there have been indications of this trying to work done to the surface. It will be interesting to see how 90L handles DMIN, as it has not been following the diurnal cycles since entering the Caribbean. Instead, 90L has been operating on the land cycles - dying out at night, developing during the day. At this time, I would give 90L a 10% chance of development within the next 48 hours.

Divergence and Convergence, something it has lacked since that impressive burst of organization the other night, is on the increase this afternoon. This will allow for lowering pressures and developing shower and thunderstorm activity. Most of the vorticity associated with 90L is in the 700-500 mb. levels, but as I said, there are indications of this working down to the surface. Pressures in the area are lowering, but that may not be a sign of 90L. Instead, it is an indication that the atmosphere ahead of 90L is favorable for further development, and this is why 90L will need to watched. It is in very high TCHP and Sea Surface Temperatures, high enough to Rapid Intensification is this were to be a tropical cyclone. As this wave moves W/WNW-ward, it will need to be watched for development. Wind shear should be favorable for the most part when entering the Gulf of Mexico, but we won't know for sure until it actually enters that area. Residents along the Gulf Coast and people in Northern Mexico will need to monitor 90L closely.

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Quoting alfabob:
Even has the pressure dropping, uh oh.


Its diurnal, pressures are supposed to fall like that this time of day.
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If you run the loop from this morning to now, this thing has turned a 180 on us as far as look wise
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This is where I see the most rotation evident:
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Keep an eye to the SW of the western tip of Jamaica
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Quoting RitaEvac:
Think ol Don might be in the cards folks, I'm gonna call it right now.


I think I agree with you. Conditions in general out front of it are improving at least for a couple days. Looks like slow development though.
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If trends continue,I would expect 90L to be reactivated.
Member Since: April 29, 2009 Posts: 75 Comments: 13931
Quoting RitaEvac:
Think ol Don might be in the cards folks, I'm gonna call it right now.


If I were rich I'd run out and buy 6 bottles of '90 Don Perignon bubbly, but I am going out and buying
two bottles for each day of rain we get in Austin. 105o here, not counting index, our lake is dying and
people are catching catfish with ticks on 'em.
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Quoting RitaEvac:
Think ol Don might be in the cards folks, I'm gonna call it right now.


no takesy backseys.

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Quoting RitaEvac:
Think ol Don might be in the cards folks, I'm gonna call it right now.


Yes, I think this is starting to chug chug on its own...as mentioned by someone else we'll have to see if it can keep chugging through D-min.
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Quoting AllStar17:
Rather stiff winds are being reported in Jamaica and Cayman Brac.


not too stiff in the brac sustained are 5-10 mph with higher gust

Link
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If they re activate ex 90L will it still be called 90L or will they change the number?
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Quoting SouthDadeFish:
Will be interesting to see how ex-90L handles d-min tonight.
convection has been on the rise as we head toward dmin. I'd guess the wave's proximity to land has been what has been allowing it to follow land convective cycles based on daytime heating, rather than typical ocean convective cycles.
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Quoting nrtiwlnvragn:
GOES East is in RSO mode, so increased number of images per hour from a GHCC Loop X 90L


looking closely at this loop notice the lower level winds south and east of Jamaica moving from ese-se to wnw-nw at a fairly good pace then look around the cayman area and just west the lower levels have slowed down considerably
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Think ol Don might be in the cards folks, I'm gonna call it right now.
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Rather stiff winds are being reported in Jamaica and Cayman Brac.
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Quoting CCstormer:
Tex/Mex Friday & Saturday, TS or low 1. We could use it but just the TS. My take, not a Met.


You may have it right. If you could spare a cloud or two for us on the upper coast would be much appreciated. :)
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Quoting Saltydogbwi1:


lol yup some maps dont even show the cayman islands the bigest island Grand Cayman is just over 20 miles long
merritt island is about 20miles long there is a bridge to the mainland.
Member Since: September 11, 2010 Posts: 1 Comments: 4268
Quoting P451:


Can't wait until RSO is standard.

Afternoon thunderstorm development over land is starting to cloud the picture now tricking the eyes on what x90L may be up to at the moment.

Just put some duct tape over cuba on your screen and that goes away.....
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Coolest day here the past 6 has been 103 degrees, 104 now and still have not reached hottest part of day yet. Humidity not too bad, heat index about 110. Not a cloud in the sky outside of high clouds.
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Quoting islander101010:
you all on that little spec on this vis.


lol yup some maps dont even show the cayman islands the bigest island Grand Cayman is just over 20 miles long
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It's turning, no denying

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