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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Quoting islander101010:
nhc is still not all that impressed
layoffs shuttle program bet the last ones to go are the garbage and f.b.i people watching them.
Member Since: September 11, 2010 Posts: 1 Comments: 5001
wow 90L up too 20%
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Give Jason another chance Taz.
He's posting some good stuff from Cape Verde this a.m. too.



Another work day! Will be interesting to check back in at 8 p.m. to see what happens today. Appears to be a lot going on.
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TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT TUE JUL 26 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A TROPICAL WAVE OVER THE
NORTHWESTERN CARIBBEAN SEA HAVE BECOME MORE CONCENTRATED THIS
MORNING BETWEEN WESTERN CUBA AND THE CAYMAN ISLANDS. SLOW
DEVELOPMENT OF THIS SYSTEM IS POSSIBLE DURING THE NEXT COUPLE OF
DAYS AS IT MOVES TOWARD THE WEST-NORTHWEST AT 10 TO 15 MPH. THIS
SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN
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90L to 20%!
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nhc is still not all that impressed
Member Since: September 11, 2010 Posts: 1 Comments: 5001
Member Since: April 29, 2007 Posts: 0 Comments: 8134
20% people...
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Quoting Tazmanian:
nhc is slow this AM lol


F5,F5,F5,F5....
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Member Since: April 29, 2007 Posts: 0 Comments: 8134
nhc is slow this AM lol
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i find JASON annyouing and what i find more annyouing is you guys Quoteing him has you vary well no i got him on Ignore
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90L is looking better and better
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1791. SQUAWK
Quoting aquak9:
JASON'S GOTTA SHOWER CURTAIN!!!


Yeah, but no fish or ponies, so he is still OK.
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this might not be a straightforward course like some have anticipated
Member Since: September 11, 2010 Posts: 1 Comments: 5001
Quoting Tazmanian:



did not feel like it


Fair enough, my man.
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Quoting NICycloneChaser:


Wow, you didn't reach 103000 last night? What happened??? Haha



did not feel like it
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Quoting Tazmanian:



well we have not had DON so you can olny say 3


Wow, you didn't reach 103000 last night? What happened??? Haha
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Quoting hurricaneben:
When was the last time we had our first 4 tropical cyclones all remain a tropical storm?



well we have not had DON so you can olny say 3
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90l is forming a surface low pressure about 50 miles ssw of the isle of youth,low level clouds can be seen being moving nw into its circulation,slow development 30% imo
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When was the last time we had our first 4 tropical cyclones all remain a tropical storm?
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90L looks good this AM
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look at Africa!
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1779. aquak9
JASON'S GOTTA SHOWER CURTAIN!!!
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Good morning.

Here is what Rob of Crown Weather has to say this morning about 90L:


Invest 90-L Continues To Be Watched For Possible Development In The Southern Gulf Of Mexico On Wednesday & Thursday
Rob Lightbown on July 26, 2011, 5:38 am

After being deactivated for a few hours on Monday, the National Hurricane Center has reactivated Invest 90-L, which is located in the northwestern Caribbean. The reason for this is because convection has increased and expanded during the overnight hours as this system has slowed down considerably in forward speed. This slowdown in forward speed has caused an increase in convergence and has also increased the chances of development into a tropical depression or a tropical storm over the next few days.

This morning’s analysis reveals that the upper level conditions and vertical wind shear values will be favorable for much of the rest of this week. Last night’s SHIPS intensity model was forecasting wind shear values to drop to 10 knots or less by later today and remain that way right through Friday. Satellite imagery this morning from CIMSS is definitely showing an increase in convection and current shear analysis reveals that the current 15 to 20 knots of shear that is over 90-L will quickly drop off as it nears the Yucatan Peninsula tonight into Wednesday where 5 to 10 knots of vertical shear exists. Surface analysis of the northwestern Caribbean shows that there is still a wave axis associated with the convection and an area of low pressure has not developed as of yet.

Ok, here are my thoughts: I expect Invest 90-L to track west-northwestward from today through Friday. This will bring this system onshore onto the coast of northeastern Mexico or south Texas on Friday night. Given the fact that vertical wind shear values of 10 knots or less are already verifying near the Yucatan Peninsula and that relatively favorable environmental conditions are forecast to exist right up to landfall on Friday night, I think that Invest 90-L will organize and develop into first a tropical depression and then a tropical storm. One thing that may really hinder development is dry air noted in water vapor satellite imagery just north of the Bay of Campeche and the Yucatan Peninsula. This really makes forecasting whether this system will develop or not very tricky.

At this point, I’m going to lean a little more on the conservative side and go with slow development into an area of low pressure possibly by late today or tonight and then slow organization and development into a tropical depression when it reaches the southern Gulf of Mexico late Wednesday night or Thursday and then a tropical storm in the western Gulf of Mexico on Friday. At this point, landfall of this system as a 45 to 60 mph tropical storm into northeastern Mexico or south Texas on Friday night is possible.

The reasons why I’m being more on the conservative side is because there is virtually no model guidance that is forecasting development into a tropical cyclone. Also, that dry air in the southern Gulf of Mexico may put a stop to any development and thus may be the reason why the models are not forecasting development.

I will be monitoring Invest 90-L very closely and will keep you all updated on the latest.

Member Since: April 29, 2009 Posts: 75 Comments: 14887
Quoting emguy:
90L: The system does not appear any better organized than it has been...at least from the stanpoint of becoming a tropical depression. I agree with that meso data based on what I can pick up on shortwave. That said, the t-storms are displaced to the east and north east. Vorticity or not, it's no closer to a classification than it was around the leewards, and the conditions do not appear all that favorable before Yucatan involvement. 90L is just a warmup wave...the season will heat up soon, especially after the downward phase of the MJO ends in second week of August. 90L = rainmaker for Cuba, Florida, and the Western Gulf...otherwise...end of story with this one.


Lmao
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Good morning, everyone! Are the models picking up any action for the next 10 days out?

Thanks and have a great day!
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1772. emguy
90L: The system does not appear any better organized than it has been...at least from the stanpoint of becoming a tropical depression. I agree with that meso data based on what I can pick up on shortwave. That said, the t-storms are displaced to the east and north east. Vorticity or not, it's no closer to a classification than it was around the leewards, and the conditions do not appear all that favorable before Yucatan involvement. 90L is just a warmup wave...the season will heat up soon, especially after the downward phase of the MJO ends in second week of August. 90L = rainmaker for Cuba, Florida, and the Western Gulf...otherwise...end of story with this one.
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slowed up
Member Since: September 11, 2010 Posts: 1 Comments: 5001
Before I'm gone...

90L appears to be developing a very weak LLC at 20N, 83.7W according to meso-analysis.

HUGE IMAGE



Extremely Hi-Res
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Quoting SCwannabe:
NHC can't decide which color crayons to use...yellow...orange...yellow...orange...maybe red

Maybe a red Lx.......
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NHC can't decide which color crayons to use...yellow...orange...yellow...orange...maybe red
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To the experts...Will the front sagging into the southeast have any influence on steering 90L/Don? or will the High dominate the steering pattern
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Quoting KoritheMan:


What part of Europe? I've never been myself.


Hopping around...

Italy/Germany

Some of my favorite places on the planet.
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i think we have a growing TS Don on our hands by later tommororw afternoon
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Nice big boomers forming around that center. we still havent got it down to the surface? Or is it on its way...LOL
Member Since: September 18, 2010 Posts: 0 Comments: 5248
Quoting Stormchaser2007:


Going to Europe for a few weeks. Family reunions and such.


What part of Europe? I've never been myself.
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Quoting KoritheMan:


Flight to where, if I may ask?


Going to Europe for a few weeks. Family reunions and such.
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1757 HurricaneHunterJoe "2mb drop in pressure in less than 4 hours at cayman."

90L's center should have been close to being over GrandCayman by now.
Unfortunately the ATCF still hasn't released its 6amGMT numbers. So we can't check any more directly than through hypothesizing about what's causing the pressure drop.
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Quoting HurricaneHunterJoe:
2mb drop in pressure in less than 4 hours at cayman. is that normal for time of day? storm related? fast or slow drop?


No, that's not merely diurnal.
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2mb drop in pressure in less than 4 hours at cayman. is that normal for time of day? storm related? fast or slow drop?
Member Since: September 18, 2010 Posts: 0 Comments: 5248
Quoting Stormchaser2007:
Gotta get on my flight soon...

I see 90L did not have a 6z update.

Odd.


Flight to where, if I may ask?
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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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