Archive for the ‘Tropical Storm’ Tag
THIS IS A VERY “TIME-SENSITIVE” REPORT
After viewing the graphic below my concerns for the residents of Tallahassee have increased; of course it goes without saying that my concerns are for everyone who might have to deal with this storm – no matter where they might be located. Mainly, there are three factors involved in my concern for the 7th most highly populated city in Florida and its capital city. One is that there is a strong chance that Hermine will become a hurricane before reaching the Florida coast.
Another: The minimum distance from Gulf of Mexico waters to Tallahassee is about 25 miles. One might consider 25 miles to be an adequate “buffer” to provide friction and thus slow down the winds approaching the city. I think that assumption would be a mistake. Furthermore, when surface or near-surface winds leave the water for land the slight slowing that might occur would tend to cause more air to rise. A similar rising is what causes lake effect snows in certain Great Lakes coastal or near-coastal downwind locations. In the case of humid winds from Hermine possibly decelerating due to friction over the land when approaching Tallahassee, the net effect could very well be more vertical cloud development (due to a greater amount of rising air) than would have occurred otherwise. This phenomenon can intensify thunderstorms, the gusts that spill out from them, and the chaos that can generate tornadoes. The increase in rainfall amounts can be dramatic. So – be careful what you wish for. Flooding is typically a bigger issue than the wind velocities in these cases.
Here is the third cause for my concern: The graphic below from the National Weather Service showing the “cone of uncertainty” (8 PM EST, 8-31-2016) causes me to consider that Tallahassee might very well be under the right-hand leading quadrant of the storm when it makes landfall. The right-hand leading quadrants of tropical cyclonic systems are usually the quadrants with the highest wind velocities, greatest probability for tornadoes, heaviest rains, and in coastal areas the greatest storm surge height. The fact that currently the whole storm is beginning to move faster can increase the danger of the right-hand leading quadrant.
I urge residents of the Tallahassee area to be alert during the approach, passage, and departure of what is now Tropical Storm Hermine. Do not take it lightly just because it is on the low side of the tropical storm wind velocity range at this time (evening of 8-31-2016).
CLICK ON THE IMAGE BELOW TO ENLARGE.
CLICK ON THE IMAGE ABOVE TO ENLARGE.
Compare this to the previous posting which was 24 hours earlier and you will see some change in the tracking model forecasts – which is to be expected.
I have greatest confidence in the TVCA run which is a consensus of 5 other models which have been good performers over the last few years. Generally, the TVCA model is very close to the National Hurricane Center’s “official” track that is the basis for the “uncertainty” cones released to the public. If you are one to pay attention to which models get mentioned or shown in weather reports you have surely heard of the “European model” which is labeled ECMWF. You won’t find it on these spaghetti illustrations; Data from this model is restricted from being redistributed according to international agreement. However, the National Weather Service official track runs very close to being the same as the ECMWF. The BAMM and related models are still useful for long term runs but in this case I think you can pretty much ignore them (the ones that run off toward the west).
Suppose you lived along the Nature Coast of Florida, (e.g. Citrus County) then you might feel that you have nothing to be concerned about because the tracks seem to be shifting northward. But please remember, these tracks are merely forecasting the storm’s center. In most cases the strongest winds are at the right hand, leading quadrant of such storms, which, in this case might cause Citrus County some concerns.
Please be sure to click on the graphic for enlargement.
The graphic above is the Friday, October 4, 2013 10 a.m CDT (advisory #6) from the National Hurricane Center.
Those who follow this web-log know that my primary source of information regarding tropical weather is Dr. Jeff Masters of Weather Underground. His blog can be found by clicking on the “community” tab once you open the following page: http://www.wunderground.com/
It would be a waste of my time and yours for me to try to explain it any better. Here is his verbatim forecast report posted at 1:44 PM GMT on October 04, 2013
Forecast for Karen
Wind shear for the next three days is expected to stay high, around 20 – 30 knots, according to the 8 am EDT SHIPS model forecast. The atmosphere is quite dry over the Western Gulf of Mexico, and this dry air combined with high wind shear will retard development, making only slow intensification possible until landfall. A trough of low pressure and an associated cold front will be moving through Louisiana on Saturday, and the associated upper-level westerly winds will bring higher wind shear near 30 knots and turn Karen more to the northeast as it approaches the coast on Saturday. The higher shear, combined with ocean temperatures that will drop to 28°C, may be able to induce weakening, and NHC has sharply reduced its odds of Karen achieving hurricane strength. The 5 am EDT Friday wind probability forecast from NHC put Karen’s best chance of becoming a hurricane as a 23% chance on Sunday at 2 am EDT. This is down from the 41% odds given in Thursday afternoon’s forecast. Most of the models show Karen intensifying by 5 – 10 mb on Saturday afternoon and evening as the storm nears the coast, as the storm interacts with the trough of low pressure turning it to the northeast. This predicted intensification may be because of stronger upper-level outflow developing (due to diverging winds aloft sucking up more air from the surface.) We don’t have much skill making hurricane intensity forecasts, so I wouldn’t be surprised to see Karen do the opposite of what the models predict, and decay to a weak tropical storm just before landfall, due to strong wind shear. In any case, residents of New Orleans should feel confident that their levee system will easily withstand any storm surge Karen may generate, as rapid intensification of Karen to a Category 3 or stronger hurricane has a only a minuscule probability of occurring (1% chance in the latest NHC forecast.)
Since Karen is expected to make a sharp course change to the northeast near the time it approaches the south coast of Louisiana, the models show a wide range of possible landfall locations. The European and UKMET models are the farthest west, with a landfall occurring west of New Orleans. The GFS model is at the opposite extreme, showing a landfall about 400 miles to the east, near Apalachicola, Florida. NHC is splitting the difference between these extremes, which is a reasonable compromise. Most of Karen’s heavy thunderstorms will be displaced to the east by high wind shear when the storm makes landfall, and there will likely be relatively low rainfall totals of 1 – 3″ to the immediate west of where the center. Much higher rainfall totals of 4 – 8″ can be expected to the east. NHC’s 5 am EDT Friday wind probability forecast shows the highest odds of tropical storm-force winds to be at the tip of the Mississippi River at Buras, Louisiana: 66%. New Orleans, Gulfport, Mobile, and Pensacola have odds ranging from 47% – 51%.
THIS IS A TIME-SENSITIVE POSTING SUBMITTED 8-21-2011 AFTER 11 PM EASTERN TIME.
IT IS NOW OUT OF DATE. PLEASE CLICK ON THE BLOG TAB AT THE TOP LEFT OF THIS PAGE AND SCROLL DOWN TO LOOK FOR A MORE RECENT REPORT ON THIS STORM WHICH IS NOW A SERIOUS HURRICANE (posted 8-22-2011 near midnight EDT).
Invest (investigation) 97L (or 97AL) has become Tropical Storm Irene. My concerns for Florida remain and it looks to me as though the east coast is the part of Florida most likely to be influenced by the system. If it does skirt the coast at least that region will be subjected to the left-hand leading quadrant which is almost always less powerful than the right-hand leading quadrant. Based upon my observation of the ECMWF (European Centre for Medium-Range Weather Forecasting) model – it now looks as though South Carolina could very well be the landfall site. Of course many changes can occur over the next few days and much depends upon the movement and strength of a trough dipping down over the Eastern U.S.A. One of my favorite sources, Dr. Jeff Masters wrote yesterday:
“The best model for predicting the timing and strength of such troughs over the past two years has been the ECMWF (European Center model). The European Center does not permit public display of tropical storm positions from their hurricane tracking module of their model, so we are unable to put ECMWF forecasts on our computer model forecast page that plots positions from the other major models. Remember that a 7-day forecast by even our best model will be off by an average of over 700 miles, so it is too early to tell what part of the U.S. might be most at risk from a strike by 97L. This weekend would be a good time to go over your hurricane preparation.”
In the future, if you wish to view the ECMWF model loops go to the right of this page and under the heading of “Tropical Weather” click on the link to Penn. State U. Models Page. Scroll down until you find it.
Here is Jonathan Vigh’s spaghetti chart effort releases at 8 pm Eastern Time, 8-21-2011.
NOTE: the CDO to which the following report refers to is “Central Dense Overcast.”
THE FOLLOWING REPORT WAS TAKEN VERBATIM FROM THE NATIONAL HURRICANE CENTER’S WEBSITE. IT WAS RELEASED AT 10 PM EASTERN DAYLIGHT TIME, 9-9-2010
000WTNT45 KNHC 070235TCDAT5TROPICAL STORM HERMINE DISCUSSION NUMBER 5NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL102010
1000 PM CDT MON SEP 06 2010
THE CENTER OF HERMINE MADE LANDFALL ON THE COAST OF NORTHEAST MEXICOAROUND 0130 UTC. PRIOR TO LANDFALL…SATELLITE DATA SHOWED THEFORMATION OF A CDO-LIKE FEATURE…WITH A LARGE AREA OF CONVECTIONALSO LOCATED NORTHEAST OF THE CENTER. THE LAST AIRCRAFT FIX AT 2333UTC SHOWED A PEAK 850-MB WIND OF 61 KT…WITH SFMR VALUES UP TO 56KT. DATA FROM THE BROWNSVILLE WSR-88D RADAR EARLIER INDICATED PEAKWINDS OF ABOUT 75 KT AT 4000 FT. THESE DATA SUGGEST THE LANDFALLINTENSITY WAS ABOUT 55 KT. SINCE LANDFALL…THE VELOCITIES FROM THEBROWNSVILLE RADAR HAVE DECREASED…AND THE INITIAL WIND SPEED ISLOWERED TO 50 KT. AS HERMINE WEAKENS…THE BIGGEST THREAT WILLSHIFT TO FLASH FLOODING FROM HEAVY RAINS AS THE CYCLONE MOVES INTO TEXAS.
THE INITIAL MOTION IS 330/12. THERE IS NO CHANGE TO THE FORECASTREASONING FROM THE PREVIOUS PACKAGE. HERMINE SHOULD MOVENORTH-NORTHWESTWARD AND THEN NORTHWARD AROUND THE WESTERN PERIPHERYOF A RIDGE OVER THE SOUTHEASTERN UNITED STATES FOR THE NEXT DAY ORSO. THEREAFTER…THE REMNANTS OF HERMINE WILL LIKELY TURN TOWARDTHE NORTHEAST AND EAST OVER THE CENTRAL UNITED STATES IN A COUPLEOF DAYS AS THE CYCLONE RIDES AROUND THE NORTHERN SIDE OF THATRIDGE. THE NHC FORECAST IS SHIFTED SLIGHTLY TO THE EAST IN GOODAGREEMENT WITH THE GFS AND ECMWF MODELS.
We are entering the peak of the Atlantic hurricane season. If you have not been influence by tropical activity thus far this year you might be under the impression that it’s an inactive season. That would not be true. Statistically, it has been about average to date. Though we cannot “plan the future” I feel strongly that we should plan “FOR” certain eventualities in the future. I urge you to be prepared and alert in the event that a tropical system comes your way.
The following statement in “blue” was taken Verbatim Thursday morning (8-19-2010) from the Dr. Jeff Masters web-log found at http://www.wunderground.com/tropical/.
“The GFS, NOGAPS, and ECMWF models continue to predict that a tropical storm will form between Africa and the Lesser Antilles Islands sometime in the period 3 – 6 days from now. There is an area of disturbed weather south of the Cape Verdes Islands, but there is no obvious organization to the cloud pattern. Wind shear is a hefty 20 – 30 knots in the region, and the disturbance is a 1 – 2 day journey away from reaching a lower shear area where development can occur. Preliminary indications are that if a storm did develop in this region, it would track west-northwest and pass well to the northeast of the Lesser Antilles Islands 7 – 8 days from now. However, 7-day forecasts of a storm that hasn’t even formed yet are not to be trusted.”
I have taken the liberty of trimming the latest full disc color satellite image down to a manageable size where you can still easily find Florida and thus look across the Atlantic to see the area of disturbed weather off Africa to which Dr. Masters refers. Two independent left clicks on this image will enlarge it fully. This image was taken from a distance over three earth diameters away from the surface yet there is considerable detail. I hope you enjoy it.
In an attempt to provide you variety in the storm track presentations, I’ve used Hurricane Alley’s version for this afternoon. Here is a link to their home page; http://www.hurricanealley.net/
One of my primary sources, Dr. Jeff Masters of Weather Underground posted the following at 4:40 pm EDT today (7-23-2010):
“The projected track will take Bonnie over the oil spill region, and the storm’s strong east to southeasterly winds will begin to affect the oil slick on Saturday morning. Assuming Bonnie doesn’t dissipate over the next day, the storm’s winds, coupled with a likely storm surge of 2 – 4 feet, will drive oil into a substantial area of the Louisiana marshlands. However, the current NHC forecast has Bonnie making landfall in Louisiana near 9pm CDT Saturday night. According to the latest tide information, this will be near the time of low tide. This will result in much less oil entering the Louisiana marshlands than occurred during Hurricane Alex in June. That storm brought a storm surge of 2 – 4 feet and sustained winds of 20 – 30 mph that lasted for several days, including several high tide cycles.”
A reference to Dr. Masters with a photograph is in the following outdated post from 2009: https://cloudman23.wordpress.com/2009/11/08/ida-forecast-11-8-09/
Here is a link to the Weather Underground Tropical Page: http://www.wunderground.com/tropical/
TO GET TO CLOUDMAN23’s HOME PAGE CLICK ON THE “BLOG” TAG ABOVE.
Those in or near South Florida including the Keys, in the Gulf of Mexico and on its shores should keep a very close watch on this weather system. Of course the tragic oil pollution disaster will likely be rendered even more problematic by what appears to be on the way.
If you have been in the habit of examining forecast cones of uncertainty from the National Weather Service – this might look a little different to you this year. There has been quite a debate over the straight black lines that heretofore have run through the cones, connecting the dots where the storms are projected to travel. Notice, on this map, such a line does not appear. Many meteorologists, myself included, believe that the lines have too often been mistaken as landfall predictions and that it has caused some people on the outer margins of the cones to have a false sense of security about where the storms might go. My guess is that some (television, websites, web-logs) will choose to stick with the old style of depictions and others will prefer to leave that center line out. I fall into the latter category.
Conditions have changed aloft such that wind shear has been reduced. This favors intensification of the system. Also, when air is heated from below, particularly if by warm water with high evaporation rates, intensification is favored. This could happen as the system moves over elements of the Loop Current of the Gulf of Mexico. What follows is a time sensitive forecast depiction of the Loop.