Ernesto strengthens as it approaches the Carolinas

Tropical Storm Ernesto is gathering strength, headed for a landfall near the North Carolina/South Carolina border late this afternoon. Radar animations from the Charleston radar shows a steadily organizing system, with a strong band of heavy rain wrapping around the west side of the center. Ernesto may have a partial eyewall and be a strong tropical storm with 65-70 mph winds at landfall. Wind observations from offshore buoys have been as high as 30 mph sustatined with gusts to 42 mph this morning. The Hurricane Hunters left the storm at 6am EDT this morning, and reported a pressure of 996 mb before they left. This is not far from Ernesto's 990 mb pressure it had when it was a hurricane with 75 mph winds south of Haiti. A NOAA Hurricane Hunter is due in the storm by noon, and an Air Force airplane at 2pm EDT.


Figure 1. Current long-range radar out of Charleston.

The north side of Ernesto is under some significant wind shear of 20 knots, thanks to southwesterly upper-level winds from the trough of low pressure pulling the storm to the north. As Ernesto moves further north, the shear will increase, likely putting a limit on the amount of intensification the storm can do. Water temperatures under the storm are about 30 C, which is very favorable for intensification. The eastern portion of the storm is over the axis of the very warm Gulf Stream Current.

Hurricane John
Hurricane John is a dangerous Category 3 hurricane this morning, just 100 miles off the coast of Mexico. The storm is moving parallel to the coast, but any deviation to the right would bring the intense core to the coast, making it one of the strongest Pacific hurricanes ever to strike Mexico. The forecast track of the storm takes it very near to the tip of the Baja Peninsula, so John has a chance to make a double hit on Mexico. John could be the strongest hurricane to affect Baja since Hurricane Liza of 1976 brushed the peninsula as a Category 4 storm. Only seven Category 4 Eastern Pacific hurricane have hit Mexico in recorded history. Wind shear is light and forecast to remain low, and sea surface temperatures (Figure 2) are a very warm 30 C under the hurricane--about 1-2 degrees C above normal for this time of year. John's strength is likely to be controlled by difficult to predict eyewall replacement cycles over the next three days, and could be a Category 4 hurricane when it encounters Baja. An Air Force Hurricane Hunter aircraft is scheduled to investigate John at 11am PDT today.


Figure 2. Current sea surface temperatures along the Pacific coast. Temperatures in the Gulf of California may not be accurate, due to difficulties retrieving the temperature via satellite measurements in such a narrow body of water. The red line separating blue colors from yellow marks the 26 C isotherm--the critical temperature needed to sustain a tropical cyclone. Note the very cool waters extending from the California border southwards along the coast. This long stretch of cool water will make it difficult for John to hold together if it tries to approach California. Image credit: NOAA/AOML.

Is John a threat to the U.S.?
In yesterday's blog, I discussed in detail the historical record of the five Eastern Pacific tropical cyclones that have affected the U.S. with tropical storm force winds. The latest model guidance still suggests the possibility John could come far enough north to affect the U.S., but it is looking increasingly unlikely. A ridge of high pressure is expected to build in and force John to the west about the time the storm reaches Baja. The GFDL model, however, takes the storm about halfway up the Gulf of California before turning it westward across Baja and away from North America.

Super Typhoon Ioke
The incredible Category 4 Super Typhoon Ioke made almost a direct hit on tiny Wake Island in the Pacific, passing just to the northeast of the island. The island experienced the eyewall of the left front quadrant of the super typhoon, but probably missed the calm of the eye. Observations from Wake showed winds of 78 mph gusting to 100 mph and a pressure of 934 mb before the instrument failed at 2:18am EDT this morning. Ioke continues to be a borderline Category 4/5 super typhoon, and is not expected to decline to category 3 strength for several more days. This would probably make it the longest-lived Category 4 or higher storm on record anywhere.

African tropical waves
The large spiral of low clouds near 18N 50W surrounded by a large cloud of dry air and African dust continues to spin, and now has some thunderstorm activity near the center. This thunderstorm activity developed last night and stayed on through the morning, an indication that the dry air surrounding this system is starting to dilute. As the environment continues to moisten, this system will have the potential for development. Development would likely not happen until Sunday at the earliest, when it should be near the northern Lesser Antilles Islands.

A tropical wave near 12N 37W, a few hundred miles southwest of the Cape Verde Islands, has changed little in organization the past day. Some slow development of this system is possible over the next few days, but doesn't appear likely.

A spinning area of clouds few hundred miles north of Puerto Rico is associated with an upper level low pressure system. Development is not expected of this system.

I'll be back this afternoon with an update. Tonight, I'll be talking live at 8:45pm EDT on the Barometer Bob show, live from northeast Florida:

http://www.barometerbobshow.com/

Jeff Masters