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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2241 & 2253:

You're sure a voice of expertise since you just joined yesterday. Have you noticed how bad of a drought TX is in?

Stop trolling, it is rather pointless.

As quakeman55 said, most of TX will take any and all rain we can get.
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Quoting ChupaCabra2011:


First time poster (not really) who comes in and right away is sarcastically criticizing others. A well deserved.
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TropicalAnalystwx13 "If it gets that high, I'm not 14. And I'm 14."

But not for long. And with the passing of each year, that not for long gets shorter.
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I say TS Don by 11pm....
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2251. Patrap
AL, 90, 2011072612, 20.0N, 83.0W, 25, 1010, DB
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Quoting TropicalAnalystwx13:


Later on today...She is going off of PDT, so it is only 8:40 AM there. If she even makes one, today...
She probably will. There's enough interesting stuff going on in the tropics to make it worth the while... not to mention the 2200+ posts in the blog so far...

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2247. Patrap
The NHC dosent post Invest's center fixes,..

They begin fixes when a Depression is declared.
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2246. 7544
has 90l stalled and if it stays there another 24 hours could the sterring change and have go thru thru the yucatan then wind up inthe gom
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Also, due to the cyclonic nature of intense storms, they tend to pull poleward unless dictated otherwise by steering.
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Quoting ChupaCabra2011:
Good Lord, you know that the tropics are dead today when you guys are devoting heart and soul to a pulp of clouds, south of the Isle of Youth, GEEZE. Also, I see that the Texas wish-casters are out in full force today, a sad turn of events on the blog today, indeed. Let em check out the long term models to see whether any of them forecast anything to form by early August.

Texas desperately needs any rain it can possibly get.
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Quoting ChupaCabra2011:
Good Lord, you know that the tropics are dead today when you guys are devoting heart and soul to a pulp of clouds, south of the Isle of Youth, GEEZE. Also, I see that the Texas wish-casters are out in full force today, a sad turn of events on the blog today, indeed. Let em check out the long term models to see whether any of them forecast anything to form by early August.
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Quoting CybrTeddy:
Stronger storm is more likely to feel a northern weakness, stronger systems have a more polar influence naturally. That's why we often see storms like Igor go out to sea and weak storms like Gaston head west.
"The beta effect on a TC can be a function of the TC size, but not necessarily the TC intensity (DeMaria, 1985). "

Here, section 1.2: http://www.nrlmry.navy.mil/~chu/chap4/se100.htm

(Which is partly why Allen-1980, Dean, Felix, etc. never did the polar movement thing).
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Where does the NHC have the center at?
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Quoting CybrTeddy:
Stronger storm is more likely to feel a northern weakness, stronger systems have a more polar influence naturally. That's why we often see storms like Igor go out to sea and weak storms like Gaston head west.

Part of the reasons we have hurricanes to begin with is to take heat and moisture from the tropics and move it poleward. That's really all it boils down to in the grand scheme of things.
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Quoting Walshy:


Until the storm forms models may be off.


Thanks, I was just curious if anyone else saw that. Just checked and the CMC shifted back towards Corpus area. I know these models jump around all the time. Was just curious if anyone had any thoughts on it. Thanks.
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2237. ncstorm
HPC Extended Discussion

MODERATE TO HEAVY RAIN IS POSSIBLE ACROSS SOUTHERN
TEXAS WITH THE TROPICAL WAVE EXPECTED TO MOVE ACROSS THE MOUTH OF
THE RIO GRANDE/BRAVO EARLY FRIDAY BEFORE DRYING OUT DUE TO
INCREASED RIDGING ALOFT ON SUNDAY. SEE THE LATEST TROPICAL
WEATHER OUTLOOKS FROM NHC CONCERNING THIS SYSTEM...CURRENTLY
SOUTHWEST OF CUBA.



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Stronger storm is more likely to feel a northern weakness, stronger systems have a more polar influence naturally. That's why we often see storms like Igor go out to sea and weak storms like Gaston head west.
Member Since: July 8, 2005 Posts: 259 Comments: 24263
weaker systems track more westerly. that why tropical waves generally move westward.

when a storm gets stronger, it try's to find any weakness so it can turn towards the north.
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Quoting Thundercloud01221991:


I believe you have this backwards... a weak system does not turn northward as easily... a ridge is weaker in the upper atmosphere allowing a stronger system to turn northward faster.... the stronger the system the more likely it is to turn northward

This ridge is more upper-level, so that pushes stronger storms more towards MX. A weaker storm will not feel the ridge as much, letting it curve north.

There isn't a trough to speak of that can impact steering significantly, so the ridge is the biggest player right now.
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Quoting TropicalAnalystwx13:


You have that backwards. The weaker the system, the farther north it will go. The stronger the system, the farther south it will go.

Right?

Stronger storms grow taller in the atmosphere and begin to "feel" the effects of steering currents in higher levels in the atmosphere, which generally tend to bring the systems farther north. For example, a strong TS or hurricane coming across the Atlantic would easily be scooped up by a shortwave pushing off the East coast; however, a weak TS or a TD lacking a strong CDO might undercut the trough and continue pushing westbound by steering currents in the lower levels of the atmosphere. That's one of the many reasons why it is so difficult forecasting the track of weak systems.
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First large band has formed on the right hand side.

If you look closely at the motion picture, it can't wait, it's already sucking in part of that right arm, midway into the wrap around, which suggests it is deepening rapidly, to me.

Watch for the hand off from the right arm to the center.



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Slow steady progress, but not shaping up to be Don the Destroyer...it's all good.

Just....bring....me....agua......
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http://www.wunderground.com/wundermap/?lat=22.97999 954&lon=-82.40000153&zoom=8&pin=Havana%2c%20Cuba&t ype=hyb&rad=0&wxsn=0&svr=0&cams=0&saLinkt=1&sat.num=1&sat.spd=25&sat.opa=85&sat.gtt1=109& sat.gtt2=108&sat.type=VIS&riv=0&mm=0&hur=0
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Link

I think COC of 90L has moved a little to WSW looking at this loop.
Member Since: April 29, 2007 Posts: 0 Comments: 7935
Gotta run! NO FIGHTING TODAY KIDS! Will see you all later tonite!
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Quoting TropicalAnalystwx13:


You have that backwards. The weaker the system, the farther north it will go. The stronger the system, the farther south it will go.


I believe you have this backwards... a weak system does not turn northward as easily... a ridge is weaker in the upper atmosphere allowing a stronger system to turn northward faster.... the stronger the system the more likely it is to turn northward
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Quoting TropicalAnalystwx13:


You have that backwards. The weaker the system, the farther north it will go. The stronger the system, the farther south it will go.

Right?


NO, i think i got it correct. The Stronger Storm will feel the trough more.
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2220. tkeith
Quoting jasonweatherman2011:
invest 90L looking better this morning
lol...nice touch with the shower curtain Jason :)
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Quoting wpb:
capital hill has the country a in a

tropical depression

That reminds me of a great Alan Jackson song...

I'm in a tropical depression
I've got the blue water blues
Can't shake this loving you obsession
Can't stand this sand in my shoes
This forgetting you vacation
Is just a fool's holiday
If I can't get over you
This tropical depression is gonna
Blow me away
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Quoting TropicalAnalystwx13:


You have that backwards. The weaker the system, the farther north it will go. The stronger the system, the farther south it will go.


Wrong
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Quoting Levi32:
High-res Visible Loop of 90L


Looks like a LLC trying to fire SE of Isle of Youth? Boomers seem to be forming in a very tight circulation?
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Quoting TampaSpin:


The Ridge is pretty much gonna hold for a weak system and keep it to a Tx/Mexico system. This will be one tho, that the stronger it gets the more Northerly it will for sure go.


You have that backwards. The weaker the system, the farther north it will go. The stronger the system, the farther south it will go.

Right?
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2215. Patrap
NHC Model Overview

Introduction

Meteorologists at the National Hurricane Center (NHC) have a variety of prediction models available to provide guidance for their forecasts of tropical cyclone tracks and intensity. The intent of this paper is to provide a brief overview of each of the models. Forecasters may find this information helpful when considering NHC discussions which mention the performance of individual models. A primary reference is provided after the summary of each model for readers who desire more information. NOTE: All thumbnail graphics in this Web document are linked to larger version of the graphics. Just click the thumbnail to view the larger version.

As noted by Neumann (1979), models for the prediction of tropical cyclone motion and intensity may be classified as either statistical or dynamical. Statistical models rely on what has happened-the climatology of past storms, for example. Dynamical models can be classified as either barotropic or baroclinic. Statistical-dynamical models are an intermediate class that incorporate numerically forecast data into a statistical prediction framework, similar to the Model Output Statistics used to provide guidance for specific parameters such as temperature and probability of precipitation.
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Quoting weatherganny:


are conditions favorable for a more northward shift? Looks like you were on the money the other nite Tampa! Great Job!


The Ridge is pretty much gonna hold for a weak system and keep it to a Tx/Mexico system. This will be one tho, that the stronger it gets the more Northerly it will for sure go.
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Quoting TropicalAnalystwx13:


True, but then it still has the death ridge to deal with.
Yep. I get that. Just pulling for some rain in central texas.
Member Since: August 16, 2007 Posts: 1 Comments: 2350
2211. Patrap
Quoting Walshy:


Until the storm forms models may be off.



The Models are tools to aid in forecasting,, the envelope and CoC are well known,,so the Models are not "off"..they use what is Known to factor out a solution downstream in time.
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Quoting ncstorm:


I posted this morning and last night about the HPC having a low off our coast by the week end..we may see development there before 90L..


90L will be making landfall in that time period.
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Quoting Patrap:


I think I see the beginning of a 'comma' shape.
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2208. ncstorm
Quoting SCwannabe:
Lots of thunderstorm activity...convection piling up off the NC/SC coast the next 24 hours...any thoughts? Kind of similar to Bret


I posted this morning and last night about the HPC having a low off our coast by the week end..we may see development there before 90L..
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2207. Patrap
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Quoting muddertracker:

This morning Levi said that if 90l can produce enough heat, it can possibly (possibly) split trough...possibly?


True, but then it still has the death ridge to deal with.
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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.