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A heat wave recap; generally quiet tropics

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

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.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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Fire weather... SE TX
a wild fire ignited yesterday in Brazoria County. Brazoria and
Wharton counties have kbdi values over 720 and kbdi values now
exceed 700 in 16 counties. The very warm temperatures and lack of
rain is again setting the stage for some critical fire weather
conditions. Winds are lighter which should help and relative humidity recovery
overnight has also been very good...but not as good as some
widespread rain
Member Since: December 31, 1969 Posts: Comments:
2005. hydrus
Quoting ProgressivePulse:

Believe it's interacting with the ULL off the FL coast.

Appears stationary and better organized..
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2004. Levi32
Good morning all.

Blog update:

Tropical Tidbit for Tuesday, July 26th, with Video
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my tropical cyclone knowledge is fairly minimal in comparison to some here, so what are the factors against 90L, that seem to convince the NHC to 'low ball' it? is it just model guidance? it looks to me like it has a real potential to become trouble, or maybe that's just flare ups from all the TCHP it's over... seems to be organizing, gaining vorticity, and perhaps stalling a little.
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2002. Patrap
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2001. bwi
Pressure drifting down at the buoy in the Yucatan channel, and winds have gone nearly calm (not common at that location).
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1999. Patrap
Updated: 4:05 am CDT on July 26, 2011
Flash Flood Watch in effect for New Orleans until 7 PM CDT this evening...

Area forecast discussion
National Weather Service New Orleans la
332 am CDT Tuesday Jul 26 2011

the main concern for this forecast package is the potential for
localized heavy rainfall again today and perhaps tomorrow and the
resulting flash flood threat. A middle level weak short wave trough
or weakness over the southeast Continental U.S. Will continue to plague the
Gulf Coast region for the next two or three days. This feature
..along with a tropical airmass in place across the region with
precipitable water values well in excess of two inches...will be
conducive for widespread showers and scattered thunderstorms with
locally heavy rainfall amounts. Some areas have seen several
inches of rain over the past week or so...in some cases over
ten inches...and additional rainfall on saturated or nearly
saturated ground could result in flooding issues. As a result...a
Flash Flood Watch will be issued for today for the entire forecast
with a general one to two inches of rain possible...although
localized rainfall amounts of three to four inches will certainly be
possible in a few areas. This watch may have to be extended or
reissued for Wednesday as the threat for localized heavy rainfall
amounts will likely continue. Rain chances will begin to decrease
at the end of the week and especially over the weekend as the
short wave trough weakens and ridging aloft builds over the Gulf
region and somewhat drier air works into the area. A tropical wave
over the northwest Caribbean is forecast to move west across the
Gulf during the week. At this time it appears that this feature
will stay south of the coast and have minimal impact on the
forecast area. 11

Member Since: December 31, 1969 Posts: Comments:

430 AM CDT TUE JUL 26 2011


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1994. Patrap
We've heard "convergence" and "Divergence" 1009 times with 90L.

We get it.
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The noodles are BACK!!!!!!!!!!!
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90L appears to be almost stationary for now!
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Convergence will probably not come about until a surface circulation appears imo.
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1989. Patrap
12z Early Cycle NHC model tracks
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)

Member Since: December 31, 1969 Posts: Comments:
Quoting TxHurricanedude11:
its been doing that w/o it for a while probaly 10 hrs i think it shouldve earlier

Believe it's interacting with the ULL off the FL coast.

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Whether it hits Mexico,TX or LA, it's gonna be Don, so get ready to check off Don on the list.
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Divergence is good!

Convergence is still missing! Invest 90L still lacks a lot in organization in the lower levels.
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Quoting neutralenso:
I just watched TWC tropical update now and mike betes talked about 90L for 14 SECONDS. he said it will bring some waves to cancun mexico thats it........ I feel bad if out of nowwhere 90L becomes a major hurricane becuase TWC takes these systems as jokes..

It is not yet dramatic enough. Stephanie wasn't on this morning, it ruined my day..
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1983. Patrap
Its my Look into da futcha
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Quoting TxHurricanedude11:

its been gaining or hold convection for quite some time now if it did it wouldve happen already

Not so. Tstorms can support themselves for a period of time, there is good divergence aloft. However, without convergence there is no rising air, thus thunderstorms will eventually burn themselves out and collapse. That process happens everyday here in FL with the seabreeze Tstorms.
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1981. ncstorm
Good Morning!! I see Invest 90L is hanging in there..I'm rooting for a Tropical Depression to head to Texas..they need the rain badly..

I noticed on the HPC surface map for 7 days that we will have a low pressure sitting off the NC coast towards the start of of the work week and the GFS is seeing one as well..

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seems to be crawling west
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Quoting Patrap:

Not much of a weakness in the high above that big low pressure. In that pattern I'd be pointing towards the Carolinas. It is a month out though, probably not all that accurate lol.
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1977. fmbill
Quoting SuperYooper:

And Leon's getting larger!

Notice how straight that line is? XTRP anyone?

I picked a bad day to stop sniffing glue! :-)
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YOu can see how the spin really has just not started.........Good Morning Everyone!
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1975. WxLogic
- ECMWF Emsemble appears to be hinting towards further development of the new wave coming out of Africa next week as it approaches the Greater Antilles.




- Due to some SAL (not much)... it could be expected to be limited in convection but as it passes 50W to 55W longitude it could pick up quite a bit as it heads WNW.

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Quoting NavarreMark:

Predict that the swirly blob known as 90L has a 40% chance of being upgraded to a spinning blob at 2. Low chance (10%) of swirly blob obtaining pinwheel blob in the next 48 hours.

tee hee's from the peanut gallery
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1970. Patrap
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Quoting P451:

I love that model. My favorite model! I always ride with XTRP.

When you ask XTRP a question, at least you can always expect a straight answer!
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1966. Patrap
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Quoting HimacaneBrees:

I'm thinking E

The CHART....

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Mowed grass last evening, fire ants are going nuts here in Galveston county. Must had 5+ ant piles in back yard, even seeing them running along the fence line where there is no grass just dirt. Huge pile in the front flowerbed up in a boxwood plant in my black mulch. Seems like the little rain we've received has them on the run.
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Quoting blsealevel:
Is it me or did the dash line get longer at the end?

And Leon's getting larger!

Notice how straight that line is? XTRP anyone?
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1960. HCW
90L model runs from the NHC. Have a great day

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1959. hydrus
Quoting DestinJeff:
New vort map:

The vort map shows vorticity west of the convection .
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1958. Patrap
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1956. Patrap
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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