Ernesto weakens; Florence forms; fires, historic heat wave in Oklahoma
Enigmatic Tropical Storm Ernesto continues westward across the Caribbean, but has weakened. Ernesto certainly looks impressive on visible satellite loops, with a symmetric shape, good spiral banding, and an upper-level outflow channel to the north and east. But this morning's flight by the Hurricane Hunters found that Ernesto had weakened, with top winds of just 50 mph, and a central pressure that had risen to 1008 mb. The storm is fighting low to moderate wind shear of 5 - 15 knots, and water vapor satellite loops show a large area of dry air to the west. Upper level winds from the west are driving this dry air into the west side of the storm. Ernesto's rains are staying just north of the ABC Islands, as seen on Aruba radar. The southern shore of the Dominican Republic is experiencing occasional heavy rains from Ernesto's spiral bands.
Figure 1. Morning visible satellite image of Ernesto taken at 8 am EDT, with echoes from a microwave satellite instrument in the 85 GHz band superimposed. Image credit: Navy Research Lab, Monterey.
Forecast for Ernesto
Ernesto continues to be a major challenge to forecast. Despite the seemingly favorable conditions for intensification expected today through Tuesday, with low wind shear, a moister environment, and increasing heat energy in the ocean, many of our top computer models refuse to predict intensification, and in fact, weaken the storm. Of the major dynamical models NHC uses operationally--the ECMWF, GFS, NOGAPS, UKMET, GFDL, and HWRF--only the NOGAPS and GFDL show Ernesto reaching hurricane strength in the Caribbean. The ECMWF dissipates the storm. However, some of the best statistical models, such as the LGEM and SHIPS, do show Ernesto becoming a Category 1 or 2 hurricane in the Caribbean. The official NHC intensity forecast of a Category 1 hurricane between Jamaica and Mexico's Yucatan Peninsula is a reasonable compromise, but the uncertainty in this is high. It would not be a surprise to see Ernesto mysteriously degrade, or undergo rapid intensification into a Category 2 hurricane off the coast of the Yucatan. Such is the state of modern hurricane intensity forecasting. Given that we don't have a very good idea of how strong Ernesto will become, making an accurate track forecast is hard. A stronger Ernesto will be more likely to feel the influence of a trough of low pressure moving to the north of the storm on Tuesday, which would pull the storm to the northwest into the Gulf of Mexico. This would likely result in a landfall in the U.S. A weaker Ernesto is more likely to head almost due west, resulting in a landfall Wednesday in Belize or Mexico's Yucatan Peninsula. This is the more likely solution, given the recent behavior of the storm.
Tropical Storm Florence forms
Tropical Storm Florence has arrived in the far Eastern Atlantic, marking the 3rd earliest date for formation of the Atlantic's sixth named storm. Only 2005 and 1936 had earlier arrivals of the season's sixth storm. The new tropical storm developed unusually quickly from a tropical wave that moved off the coast of Africa just two days ago, and the storm's formation was aided by a pulse warm ocean water and associated low pressure called a Convectively Coupled Kelvin Wave (CCKW.) The SHIPS model is diagnosing a moderate 10 - 15 knots of wind shear over Florence, and predicts that the shear will stay in the moderate range over weekend, then increase to the high range as Florence encounters an upper-level trough of low pressure. The latest Saharan Air Layer Analysis shows that a large area of dry air lies to the north and west of Florence, and this dry air will likely cause problems for the storm. Ocean temperature are near 26 - 26.5°C, which is right at the threshold for where a tropical storm can typically exist. The predicted steering current flow for Florence does not favor a long-range threat to any land areas.
Historic heat wave in Oklahoma
A historic heat wave and drought fueled raging fires on Friday in Oklahoma. The fires destroyed at least 65 homes, forced multiple evacuations, and closed major roads. Oklahoma City had its hottest day in history, hitting 113°, tying the city's all-time heat record set on August 11, 1936. The low bottomed out at 84°, the warmest low temperature ever recorded in the city (previous record: a low of 83° on August 13, 1936.) Oklahoma City has now had three consecutive days with a high of 112° or higher, which has never occurred since record keeping began in 1891. With today's high expected to reach 113° again, the streak may extend to four straight days. Yesterday was the third consecutive day with more than a third of Oklahoma experiencing temperatures of 110° or higher, according to readings from the Oklahoma Mesonet. NOAA's Storm Prediction Center (SPC) declared a "Critical" fire weather day over most of Oklahoma yesterday, due to extreme heat and drought, low humidities, and strong winds. Between 4 - 5 pm CDT Friday, Oklahoma City had a temperature of 113°, a humidity of 12%, and winds of 14 mph gusting to 25 mph. Another "Critical" fire weather day has been declared for Saturday. A cold front approaching from the northwest will bring winds even stronger than Friday's winds, and Oklahoma will likely endure another hellish day of extreme heat, dryness, and fires.
Figure 2. The Geary, Oklahoma fire, looking north, on August, 3, 2012. Image credit: Oklahoma City Fire Department. The Geary fire spawned a gustnado.
Only comparable heat wave: August 1936
The only heat wave in Oklahoma history that compares to this week's occurred in the great Dust Bowl summer of 1936, the hottest summer in U.S. history. Oklahoma City experienced three days at 110° that summer, and a record streak of 22 straight days with a temperature of 100° or hotter. Those numbers are comparable to 2012's: three days at 110° or hotter, and a string of 17 consecutive days with temperatures of 100° or hotter. It's worth noting that Oklahoma City has experienced only 11 days since 1890 with a high of 110° or greater. Three of those days were in 2011, three were in 2012, and three were in the great Dust Bowl summer of 1936. Clouds moved in over Tulsa, Oklahoma yesterday, holding down the high temperature to just 107°, ending that city's 3-day streak of 110°+ days. The only longer streak was 5 consecutive days on August 9 - 13, 1936.
Figure 3. Most of Oklahoma has experienced eight consecutive days with highs of 100° or more, and many regions, including Oklahoma City, have had a streak of 17 such days. Image credit: Oklahoma Mesonet.
Jeff Masters
Reader Comments
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Carolinas coasts. Live video feed from Charleston, SC
That was a good laugh!!! Lmao!
Mars is getting all da Bandwidth...and Press.
Opportunity has a HUGE audience coming up.
:P
I'm just an interested amateur, but I've been on here during the active part of the season for years, and the impression I get is that 'lack of vertical instability' aka 'sinking air', may be an underrated factor inhibiting cyclogenesis and preventing existing storms from intensifying.
Dr. Masters touched on the subject last year to explain why so many storms which were predicted to intensify, didn't. He's produced graphs for this season which show that vertical instability this year is lower than average throughout the hurricane zone. This is believed to be due to the ongoing drought and high pressure in the US.
I think it may be a factor that isn't fully appreciated by mets. No idea to what extent the models incorpoate it, but I suspect they underestimate its importance. I do think Ernesto will be inhibited by sinking air. There's also a big area of 20knts of wind shear between Mexico and Cuba.
and the dry air to its shrinking so it wont be long till he takes off!
Please edit this comment, language like that is not tolerated around here.
No one will comment on this because they do not want to believe it.
Sigh.
Nice satellite picture in motion!
I particularly did not want to see it considering I have that person on ignore.
I've been watching it every chance I get. I've been busy. There were signs early this morning that dry air would be ingested, and it was, but there are no signs at this time. Dry air will have a minimal impact on the system at best.
Ruff!
Keep trying to post this image...
Yeah I posted as well and got nada..I mean now the HPC is on board with a western movement..Ernesto better have some good tricks up its bag if it wants the GOM..
Notice the outflow on the northwest side with clouds being pulled towards the Florida weakness. This should have a gradual tug on Ernesto pulling it slightly more northwards. Apparently, the GFDL/HWRF are seeing this unlike the others. Easily seen on the water vapor loop below.
WV LOOP
Had a great orientation last two days, can't believe I missed so much of Ernestos intensification.
Can someone tell me how to post a graphic. I am clicking on "Image" and typing in the URL address.
Can I not post JPG images? Ugh!!
Yeah, slightly. It has been for the past 24 hours. Probably established a true WNW movement by now as well.
GFDL weakens ernesto but the interesting thing is ernesto goes to far to the south and then even with that, he takes ernesto to north GOM
Gotta right click the image and copy image URL, then paste in the image box on Wunderground.
From what I've gathered, that's not the case. The models are showing the ULL actually backing away and Ernesto gets into a favorable environment. The NHC have even acknowledged that conditions will be favorable.
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