Tuesday, August 28, 2012

Isaac's Biggest Threat: Water

Update: 1:35 a.m. EDT August 29,

The eye seems to have stalled off the coast of Grande Isle, LA.  It seems to be doing a loop on radar and this will delay landfall.  Much of southeastern Louisiana will be pounded by high winds, heavy rains, and storm surge for much of Wednesday.

The radar view from Slidell, LA at 1:05 a.m. EDT, August 29, 2012.

As Isaac makes landfall in southeastern Louisiana it is likely to be a category 1 hurricane.  This may not sound like much, but the winds are still a danger and shelter will be needed.  However, it is the water, both surge and rain, that are the biggest threat.  The storm is expected to slow down as it moves through southeastern Louisiana and could produce rain through Wednesday night.

The forecast for Isaac as of 11 a.m. EDT, August 28, 2012.  Click on the images for a larger view.  Image Credit: NOAA/NHC.

At 11 a.m., Tuesday, Isaac was still a tropical storm; however it was close to becoming a hurricane with maximum sustained winds of 70 mph.  This is strong enough to take out trees and power lines with some minor structural damage to buildings.  The satellite picture below showed the storm getting better organized, but the bulk of the rain was east and south of the center.

Sunday, August 26, 2012

Isaac Is Now In The Gulf

Key West is normally a festive place particularly leading up to Labor Day.  Tonight it is a different place.  Webcams show only a few cars on the road on only a few brave souls on the streets.  Any partying is being done indoors.  It has been a rainy and windy day in Key West with gusts frequently up to 40 mph.  Peak gust occurred at 1:22 p.m. with winds to 47 mph.

Image from a webcam in Key West, FL.  Image Credit: WebcamViews.com

Isaac took a turn to the west-northwest for much of the day taking it through the Florida Straits.  It passed south of Key West late this afternoon instead of going through the Keys.  At 8 p.m. EDT on Sunday, the storm was located about 60 miles southwest of Key West moving west-northwest at 15 mph.  Maximum sustained winds were about 65 mph making it a tropical storm.

Saturday, August 25, 2012

Isaac Heads For The Gulf

Last night Isaac moved across Haiti dumping torrential rains on the poorest country in this hemisphere.  High winds and flooding rains pounded the country into the morning hours.  The center of Isaac moved across the southern mountains of Haiti, but then turned northward through the Windward Passage to reach the eastern tip of Cuba by midday.

Click on image to enlarge.  Image Credit: NOAA/NHC.

This is the latest plot of the path of Isaac with the associated wind field.  Notice how erratic the path has been since moving into the Caribbean.  This is due to the complex weather pattern over the region playing a tug-of-war with the storm and it is still happening.

Thursday, August 23, 2012

Isaac Is A Difficult Call

Tropical Storm Isaac moved into the eastern Caribbean Tuesday afternoon and was moving westward during the evening.  The storm was getting better organized late in the evening, but the winds were not much different from earlier in the day.  It is only a matter of time before the winds respond to the drop in pressure.

Tropical Storm Isaac at 0215z August 23, 2012.  This is an enhanced infrared picture of the storm.  The dark areas represent the colder cloud tops meaning that they are higher in the atmosphere.  Image Credit: NESDIS.

There has been considerable concern about the future of this storm due to the impact it could have on Florida and the Republican National Convention in Tampa next week.  Any evacuation would greatly alter the plans for the convention.  A general idea of where the storm is going can be gleaned from the models.  However, the devil is in the details.  It is far too uncertain at this time frame to pin down where the storm will strike land.

Saturday, August 18, 2012

ICE vs STORM: 2012's Great Arctic Cyclone

The Arctic region is warming twice as fast as much of the rest of the globe.  This is transforming the climate and the weather.  A storm earlier this month portents much of what can be expected as the sea ice melts.  In fact this storm may have hastened the melt, but this is still an open question.  The following is a very interesting article posted on NCAR's website.

By Bob Henson

As Shakespeare noted about true love, the course of Arctic sea ice never does run smooth. Even though weather conditions in June and July weren’t especially favorable for melting, the ice vanished at a striking pace. Then came a midsummer tempest—and now 2012 threatens to break 2007’s records for the lowest extent of Arctic sea ice ever observed.

I knew something was afoot when I turned to the indispensible Arctic Sea Ice Blog a few days ago and saw the headline “Cyclone warning!” Computer models were indicating that a vast, powerful area of low pressure would develop over the central Arctic Ocean and stay in place for days. The storm didn’t last quite as long as forecast, but it was indeed a humdinger, one that could stimulate research for years to come.

This mosaic of NASA/MODIS satellite images from August 5 shows a massive low-pressure center spinning across the central Arctic Ocean on August 5, 2012. Canada and Alaska are located to the left, with Europe and Russia to the right. (Image courtesy NASA Earth Observatory.)

Monday, August 13, 2012

Midwest Gets A Break From The Heat, But Not The Drought

It has been a brutally hot summer from the Midwest to the southern Plains.  Add to this the lack of rainfall and you have the recipe for a devastating drought.  What was expected to be a record year for corn is likely to be the worst in decades.  The drought expanded quickly as all-time record highs were being set; some dating back to the Dust Bowl.

Look at two cities caught in the heat wave and drought.  Oklahoma City has endured 28 days from late June to mid August of 100 degree temperatures.  St. Louis has recorded 21 days during the same period.  Both cities tied their all-time record high temperatures at some point during the heat wave.

Now Mother Nature is about to give the central and eastern parts of the country a break from the heat.  A low pressure is going to develop aloft and become centered just south of Hudson Bay by early next week.  As the map below shows winds in the upper atmosphere will dip south into the U.S. bringing a cooler Canadian air mass.  If this were winter there would be talk of a cold wave, but this is summer and we will call it refreshing.

The forecast for winds at 500 mb (about 18,000 ft) for Monday, August 20, at 18z.  Click on the image for a larger view for all of the graphics.  Image Credit: NOAA/NCEP.

Thursday, August 9, 2012

South Carolina Drought Update

Three months ago 99% of South Carolina was in a moderate drought or worse.  About 35% was in an extreme drought and it seemed to be getting worse.  Then the rains began to appear in mid-May.  This continued through mid-June and then the rains stopped.  It became brutally hot with some areas breaking all-time record highs.  The corn crop in the western part of the state suffered from the flash drought conditions.

The heat continued through much of July and it was the third hottest July on record for South Carolina.  We joined much of the central and eastern part of the country in that respect.

Average July Temperature rankings.  Image Credit: NOAA/NCDC.
Rains continued to fall across July with Columbia receiving over 9 inches of rain in the city.  The heavy downpours resulted in several instances of flooding of Rocky Branch Creek.

Flooding of the Rocky Branch Creek on June 11, 2012.  Image Credit: USGS.

It also occurred in June from some heavy rains in the middle of month.  This was a bit ironic occurring in the midst of a drought.  However, there have been five extreme rainfall events at the airport and city in the past three months.

Wednesday, August 8, 2012

Ernesto Makes Landfall

Ernesto became the second hurricane this season yesterday afternoon.  Moving west-northwest the storm made landfall on the Yucatan Peninsula east of Chetumal, Mexico.  The official landfall was about 11 p.m. and maximum sustained winds were estimated at about 85 mph in squalls northeast of the center.  Minimum pressure was 980 mb (28.94 in.).

The top picture is an enhanced infrared satellite photo.  Image Credit: NESDIS.  The bottom picture is of Ernesto making landfall from the Doppler Radar in Belize City.  The hurricane is into the top portion of the screen.  Image Credit: Belize National Meteorological Service.  Click on either picture for a larger view.

Friday, August 3, 2012

Ernesto Approaches Barbados

Tropical Storm Ernesto formed in the tropical Atlantic east of the Windward Islands Wednesday afternoon.  Hurricane hunter aircraft found tropical storm force winds even though satellite pictures did not indicate as much organization.  Ernesto was nearing the island of Barbados just after midnight on Thursday morning.  The storm had maximum sustained winds of 50 mph and was moving west at 22 mph.  The latest National Hurricane Center advisory can be found here.

Tropical Storm Ernesto approaching Barbados.  Click on the image for a larger view. Image Credit: NOAA/NHC.
Ernesto will pass through the Windward Islands this morning and head into the Caribbean Sea.  Conditions do not favor significant strengthening over the next few days and the computer models are tightly clustered around a westward path.

Computer model forecasts of the center of the storm.  Image Credit: NCAR.