Archive for the ‘Wind shear’ Tag

IDA FORECAST – 11-8-09

Some of the information on this site is published close to “real-time”  particularly as it applies to tropical weather.  But it is important to remember that the only “official” source of information is the National Hurricane Center. Decisions concerning life or death, property, and such should not be made based solely on the information found on this site or any other sites that are recommended here. unless they are official. Listen to your local authorities when conditions are life-threatening or there is possible loss of property.


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THE ENTIRE FIRST PARAGRAPH THAT FOLLOWS  IS A DIRECT QUOTE FROM DR. JEFF MASTERS (PICTURED BELOW) THAT WAS CUT AND PASTED FROM HIS WEATHER UNDERGROUND SITE; DR. MASTERS IS MY MOST RELIABLE AND DEPENDABLE SOURCE WHEN IT COMES TO TROPICAL WEATHER; HE IS A DEDICATED ‘WINNER:”  ONE REASON WHY I DEPEND SO HEAVILY UPON HIS WORK IS THAT HE IS NOT OPERATING UNDER THE CONSTRAINTS OF NATIONAL WEATHER SERVICE FORECASTER BUT HE BENEFITS FROM THEIR INTERPRETATIONS AS WELL AS FROM OTHER NATIONAL WEATHER SERVICE RESOURCES.  HE IS DEDICATED, “UP FRONT,” AND RESPONSIBLE.

bio_jeffm
Dr. Jeff Masters

The forecast for Ida


Posted: 10:21 AM EST on November 08, 2009


“The high wind shear of 20 – 25 knots currently affecting Ida is forecast to persist at that level until Monday night. Some slow intensification is still possible while Ida remains over the exceptionally warm water of the Loop Current in the Gulf of Mexico, through tonight (Figure 2). Late tonight, Ida will be crossing over waters of 26°C, which is barely enough to support a hurricane. With shear still expected to be at 20 -25 knots, I expect weakening to begin early Monday morning and accelerate on Monday afternoon. At that time, Ida will encounter 40 knots of wind shear associated with a cold front over the Gulf of Mexico, and begin transitioning to an extratropical storm. Exactly how strong Ida will be when it reaches the coast early Tuesday morning–and indeed if Ida even does reach the coast–is a forecast with high uncertainty. The computer models have a tough time forecasting the evolution of a tropical cyclone into an extratropical cyclone, and the models are all over the place on what will happen. Most of the models foresee a landfall near 1 am EST Tuesday between Mississippi and Pensacola, Florida, then a path northeastward over the Southeast U.S. However, Ida could come to halt before reaching the coast and turn west towards Tampa (the UKMET model’s forecast), or turn south back over the Gulf of Mexico (the NOGAPS model’s forecast). In any case, storm surge and heavy rain appear to be the main hazards from Ida. The GFDL model (Figure 3) is forecasting rain amounts of 4 – 8 inches for a large swath of the Gulf Coast, and there is a risk of tornadoes if the warm air from the core of Ida pushes ashore.”  END QUOTE

From my point of view, (this is Cloudman23 writing) everyone on the Gulf Coast  from Mississippi to Key West should have a “heads up” mindset while Ida is out there.  As Dr. Masters said, the computer models have a difficult time when the tropical to extratropical metamorphoses takes place.  Furthermore, the chance of tornadoes (mentioned by Dr. Masters) in association with warm, moist air from Ida and its inherent instability in such situations, this storm should not be taken lightly.

11-8-09 Ida 3pEST

TROPICAL DISTURBANCE – JULY 20, 2009

LEFT CLICK TO ENLARGE THIS IMAGE

LEFT CLICK TO ENLARGE THIS IMAGE

TIME SENSITIVE! – THIS WAS POSTED AROUND

11:30 PM EST

ON JULY 20, 2009.

A tropical disturbance (also known as a tropical wave) has moved over Barbados and is continuing on its general path toward a direction just a little north of west.  The image above is a color-enhanced infrared.  At the time of this posting, the National Hurricane Center is indicating that they do not expect development into a cyclonic system within the next 48 hours.  To be cyclonic there must be a closed rotation.  tropical depressions, tropical storms, and hurricanes rotate counterclockwise in the northern hemisphere (except in the higher levels of the storms).  For more information on cyclonic circulation in a hurricane go to this link:

https://cloudman23.wordpress.com/2008/09/09/hurricane-circulation-lesson-1/

My most trusted source, Dr. Jeff Masters, at this time expects the disturbance to be torn apart by upper level wind shear within the next few days.

To follow Dr. Masters’ reports, go to the following link:

http://www.wunderground.com/cgi-bin/findweather/getForecast?query=34442

Then, in the “Features” bar at the top, click on Tropical/Hurricane.

That will take you to his Wunderblog feature which usually appears on the right hand side of the page.

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but are unable,

please click on the “blog” tab

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Florida Tropical Weather Outlook for November – 2008

LEFT CLICK TO ENLARGE IMAGE

TWO SINGLE LEFT CLICKS WILL ENLARGE IMAGE ADEQUATELY

THIS CHART IS TIME-SENSITIVE,

AS ARE MOST CHARTS PROVIDED IN THIS WEB-LOG SITE.

Vertical wind shear is defined as the change of the wind (velocity or direction or both) with changes in altitude. Vertical wind shear, particularly in velocity, is a significant factor in the probability for tropical system intensification, or weakening.  Here is a general rule of thumb on that subject: The probability of intensification increases when vertical shear is 20 knots or less – and when shear exceeds 20 knots there is a decrease in the probability of intensification.

The graphic that I have provided (above) shows the wind shear forecast for tomorrow afternoon – Saturday, November 1, 2008, Eastern Time.  I recommend two single left clicks upon the image to enlarge it adequately.  I have marked some belts of high shear and low shear and I have also placed a white arrow on the scale at the bottom of the map showing 20 knots which is about 10.29 meters per second.

It is expected that for the first half of the month high wind shear will protect Florida from storms that might develop over the typical late-season hurricane breeding sites.  If this forecast pans out, it is not likely that the Gulf Coast states will see tropical action for that portion of the month.  However, storm probabilities, with respect to vertical wind shear, may increase during the second half of the month.  Of course there are other factors – e.g. – sea surface temperatures.  I will address that soon.

Living in Florida, hurricanes are of great concern to me.  Members of my family depend upon me to provide as safe a home as possible.  Even though a storm threat seems unlikely for at least the next two weeks, and we are well into the period of steady decline in tropical weather activity, I have no intention of letting my guard down any time soon and this is what I recommend for you if you live in a hurricane-prone region.  Some very impressive storms have occurred in November.

NOTE: I have tried to help you get your bearings geographically by marking Florida – not because I felt that you couldn’t find it but because the deep color contrast obscure the geographical outlines.  I simply wanted to make it as easy for you as possible in the event your eyes are as bad as mine.  LOL

NORBERT IS MOVING TOWARD THE NORTHEAST, 10-12-08

LEFT CLICK IMAGE TO ENLARGE

LEFT CLICK IMAGE TO ENLARGE

LEFT CLICK IMAGE TO ENLARGE

LEFT CLICK IMAGE TO ENLARGE

IMAGES ARE TIME SENSITIVE!

Norbert has reached the mainland of Mexico after recently ripping though the Baja peninsula.  It’s strength is likely to diminish quickly but it will maintain tropical storm intensity for quite some distance into Mexico and could easily effect weather in west Texas and New Mexico early this week.  Notice that the storm is now elongated (oval, rather than circular).  The elongation is along the axis of wind shear which is depicted in the second image which was completed about two hours earlier than the first image.  So, the two images are not a perfect match-up but they are close.  It looks as though the storm is likely to continue traveling 40 to 45 degrees east of due north along the direction of winds aloft.

Hurricane Kyle Is Heading Northward Toward Maine and Nova Scotia

Source = National Hurricane Center

Source = National Hurricane Center

Left click to enlarge this image.

At 8 PM EDT this evening Kyle still was maintaining hurricane strength in spite of high wind shear aloft.  Generally, a 15 mph wind shear is about the break-off point for being slow enough to allow a hurricane to hold its strength or intensify.  It has been greater than that today and is expected to get up to 25 mph tomorrow.  However, the winds over the storm are diverging as two cars going down the highway together would diverge a bit if one of them were to move to a lane further from the other car.  So, the air over the storm is moving in the same general direction but spreading a bit.  When air aloft converges it tends to sink and the opposite happens when air aloft diverges; there tends to be an increase in the amount of air rising from below.  This could allow Kyle to maintain hurricane strength tomorrow in spite of the shear.  It’s a fine balance and there is some disagreement as to whether it will still be a hurricane tomorrow since at 8 PM the maximum sustained winds were 75 mph and 73 mph would demote it a tropical storm.

It will be interesting to see what happens.  Of course, for the sake of the landfall regions and the ships and boats at sea in that area, I hope it weakens quickly.