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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Haha. :P You know what I was talking about.
Growing more compact and organized around the center rather than spread out.
The NHC uses 65 mph. They don't use 55 mph.
I thought that was 55.
Coordinates: 17.7N 64.7833W
Acft. Static Air Press: 976.6 mb (~ 28.84 inHg)
Acft. Geopotential Hgt: 337 meters (~ 1,106 feet)
Extrap. Sfc. Press: 1015.0 mb (~ 29.97 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 113° at 20 knots (From the ESE at ~ 23.0 mph)
Air Temp: 24.8°C (~ 76.6°F)
Dew Pt: 23.4°C (~ 74.1°F)
Peak (10s) Flt. Lvl. Wind: 21 knots (~ 24.1 mph)
SFMR Peak (10s) Sfc. Wind: -
SFMR Rain Rate: -
(*) Denotes suspect data
Recon in the air.
05L/TS/E/CX
R.I.FLAG OFF
MARK centre of image
15.00N/72.00W
I'm not referring to how the NHC classifies systems. I'm referring to the actual winds in Ernesto.
So has recon left yet? :P
Florence will be interesting to watch from a cyclogenesis point of view but I'd be shocked if it ever seriously threatens the CONUS.
No, they use 65. It's 55 that they don't normally use. Because 45 knots equals about 50 mph and 50 knots equals about 60 mph. 55 mph is skipped in the conversions but 65 mph isn't. (55 kts rounds roughly to 65 mph)
I'm watching the low off the CVI
18z Early Cycle NHC model tracks
Ernesto
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
Early Model Wind Forecasts
1. Not an open wave. Not remotely close to being an
open wave; meets every criteria for current
status, nor will it be an open wave anytime soon
2. South side inhibited by land interaction
diminishing
3. Warmer SSTs and higher TCHP
4. Shear, not a problem
5. Dry air becoming less of a factor
6. Ernesto generating its own moisture field
7. Outflow improving, wind field expanding
8. Nice looking CDO, not imaginary, and it's improving
9. Banding features improving
10. Nice, robust circulation
11. Monsoonal trof moisture still feeding the system
12. Upper level high pressure, anticyclone aiding
ventilation
1/2 dozen things it needs to aid development:
1. Slow forward speed
2. Improve low level convergence
3. Continue expanding moisture field
4. Larger surface center for better updraft and
cycling out dry air to its west
5. Get more symmetrical
6. Get more vertical
From 142° at 37 knots
(From the SE at ~ 42.5 mph) 7.5°C
(~ 45.5°F) -11.7°C
(~ 10.9°F) 39 knots
(~ 44.8 mph
And Ernesto and Florence are both beautiful on Google Earth... just wow.
I can see what the models are seeing. The models have this as a shallow system. It barely has any presence at 500mb, and the 500mb vorticity that does exist has a small diameter capable of missing the upper level westerlies. This track issue is an intensity issue.
Long-term track is not certain but it is primed for somewhere in the South-Central to western gulf...Whether it moves west into Mexico or comes a bit farther north remains to be seen...keep staying updated
Thought 2: we've got a large upper low over the gulf right now and it's not moving anywhere fast. It will get out of the way a bit, but I doubt it would be able to get all the way out of the way. It would pretty much need to substantially weaken and move SW into the Pacific to get all the way out of the way.
I'm still favoring a right hand turn as well...
it's even better when you get live (or close) sat images from nrlnavy! Did it this morning.
Transmitted: 4th day of the month at 22:13Z
Date: August 4, 2012
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 307)
Storm Number: 05
Storm Name: Ernesto (flight in the North Atlantic basin)
Mission Number: 5
Observation Number: 02
22:14:30Z 17.583N 65.233W 540.4 mb
(~ 15.96 inHg) 5,279 meters
(~ 17,320 feet) - 286 meters
(~ 938 feet) From 95° at 25 knots
(From the E at ~ 28.7 mph) -2.7°C
(~ 27.1°F) -8.3°C
(~ 17.1°F) 26 knots
(~ 29.9 mph) - - - -
Time Coordinates Aircraft
Static Air Pressure Aircraft
Geopotential Height Extrapolated
Surface Pressure D-value Flight Level Wind (30 sec. Avg.) Air Temp. Dew Point Peak (10 sec. Avg.)
Flight Level Wind SFMR
Peak (10s Avg.) Sfc. Wind SFMR
Rain Rate Estimated Surface Wind (30 sec. Avg.)
Using Estimated Reduction Factor Peak Wind at Flight Level to
Est. Surface Reduction Factor
HDOB Observations
Independent Calculations from Tropical Atlantic
At 22:05:00Z (first observation), the observation was 99 miles (160 km) to the ESE (120°) from San Juan, Puerto Rico (USA).
At 22:14:30Z (last observation), the observation was 79 miles (127 km) to the SE (136°) from San Juan, Puerto Rico (USA).
the musical selection was quite entertaining..
Recon will tell.
Yellow circle @ 8am ??
Yucatan to get plowed by a hurricane. Not clipped.
Louisiana eastward has been written off from me.
Texas is as far north as I am going. There is no way in hell it goes to any other US state along the GOM. Mexico also has a high chance of being directly hit.
Take it for what it's worth, I am not a alarmist, I am a realist.
The GFS fields show a trough at 500mb.
Soon-to-be 92L? Probably so.
Viewing: 1501 - 1551
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