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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major hurricane ? not a ch
Hey TA13, I always appreciate your analysis because if you disagree or don't understand you give your reasons. I've never seen you pull something out of ...uh ummmm...a can of speculation and present it as fact. You have excellent reasoning skills and aren't reluctant to admit error, so hats off to you. I mean that sincerely.
The best thing I've learned from the Ernesto discussions is if the storm is not doing what it "should" be doing, then there are some puzzle pieces missing in our analysis - meaning it's time to sit back and take another look. Weather is complex but it's not magic...changes in it are due to identifiable forces. Trying to identify and account for all complex forces acting on a system is like trying to juggle 27 balls at once - it's easy to drop a few. Don't disbelieve or absolutely believe the models, try to understand the "why" of the model predictions. Just my two cents...and I'll even give ya change. :-)
its even worse..
so does my local met kirk
that high is pretty strong too, but if that system gets strong quick enough, it will probably go out to sea
I'm thinking I'm seeing multiple vortices. Decoupled? May be now. Look seast of the the exposed LLC.
VISIBLE LOOP
well it wont recurve for a while...we'll have to see if the western edge of the high stays weak enough for it to recurve in time...
That's another story in itself! LOL ;-)
High to the north moves "Gordon" due west
could see watches and warnings of some kind for the Cape Verde Islands as the system is moving off the coast of Africa, since the GFS shows the system going right over them
Daily Atlantic Tropical Analysis
Chicklit: Your comment about the Low in the BOC on post 3807. Could you answer my above question for me pleas?
1) Ernesto fully dissipates over the Yucatan/CA?
2) Ernesto begins to slightly strengthen before hitting the Yucatan, but then weakens due to land interaction. The weakening trend causes a center reformation - changing the track forecast as he re-emerges in the Gulf?
The reason I mention scenario #2 is because climatologically this happened several times in the past.
NOUS41 KWBC 251842 AAB
PNSWSH
Technical Implementation Notice 12-22, Amended
National Weather Service Headquarters Washington DC
342 PM EDT Wed Apr 25 2012
Effective on or about Tuesday, May 22, 2012, beginning with the 1200 Coordinated Universal Time (UTC) run, the National Centers for Environmental Prediction (NCEP) will upgrade the GFS model and its associated data assimilation system (GDAS). The primary changes will be to the analysis system. There will be no major changes to the GFS model itself, but there will be a few modifications to the output products available from the GFS.
The primary change to the operational GFS and GDAS will be in the analysis system. The major component of the analysis change will be the incorporation of a hybrid variational/ensemble assimilation system. In this system, the background error used to project the information in the observations into the analysis is created by a combination of a static background error (as in the prior system) and a new background error produced from a lower resolution (T254) Ensemble Kalman Filter. The development of this system was done in collaboration with PSD at ESRL. The inclusion of this change and the other smaller changes listed below produce significant positive impact on forecasts in both the northern and southern hemispheres and in the tropics. In almost all measures, a positive impact is noted; however, during the summer (convective precipitation) season, a small consistent degradation of the rain/no rain line and an increase in the bias was noted. This problem will be addressed through modifications to the convective parameterization in the next global implementation.
GFS Model Changes:
The global spectral model is restructured, but there are no major physics or dynamics changes except for some bug fixes. The impact of these changes on the forecast is at the machine round off level.
Link
168 hours, ridge continues to intensify to the north and the storm is moving due west
Even cmc is better than it used to be.
Beautiful day to be in the Bahamas.
Viewing: 3851 - 3895
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