Cristobal a Hurricane; Little Change to 97L

It doesn't look much like hurricane, but the Hurricane Hunters measured surface winds around 75 mph on Monday evening and Tuesday morning in Hurricane Cristobal, making it the third hurricane of the 2014 Atlantic hurricane season. These missions proved the value of hurricane hunter flights, since there is no way that we would have known Cristobal was a hurricane based on satellite data. The storm is stretched out in a long line of heavy thunderstorms, has no eye or low-level spiral bands, and is giving early August's Hurricane Bertha some stiff competition for ugliest Atlantic hurricane of the century. Along with Hurricane Arthur and Hurricane Bertha, Cristobal gives us three Atlantic hurricanes so far this year, exceeding the entire 2013 Atlantic hurricane season total. The second (and final) hurricane of the 2013 season (Ingrid) did not arrive until September 14. On average, the third hurricane of the Atlantic season arrives on September 9, and the third named storm of the year on August 13. The last time the first three named storms in the Atlantic became hurricanes was in 1983, when Alicia, Barry and Chantal all became hurricanes (if we exclude 1992, when an unnamed subtropical storm formed prior to the arrival of Hurricanes Andrew, Bonnie, and Charley.) Cristobal continues to dump heavy rains over the Central and Southeast Bahamas and Turks and Caicos Islands as the storm heads northeastwards out to sea. Satellite loops show that Cristobal is struggling with wind shear, with a center of circulation partially exposed to view, and all the heavy thunderstorms pushed to the south and east sides of the center. The only land area at risk from Cristobal is Bermuda, and the 5 am EDT Tuesday Wind Probability Forecast from NHC gave that island a 27% chance of experiencing tropical storm force winds of 39+ mph. The GOES-14 satellite is in rapid-scan mode over Cristobal on Tuesday, and you can access an impressive 1-minute resolution satellite loop of the storm from the NOAA/RAMMB website.


Figure 1. MODIS true-color image showing Tropical Storm Cristobal's intense thunderstorms stretching from the Southeast Bahamas to Bermuda at 2 pm EDT on August 25, 2014. At the time, Cristobal had top winds of 60 mph. Image credit: NASA.

Little change to 97L headed towards the Lesser Antilles
A tropical wave (Invest 97L) was near 13°N, 47°W on Tuesday morning, about 900 miles east of the Lesser Antilles Islands, and was headed west to west-northwest at about 15 mph. Satellite loops show the wave has changed little since Monday, and has a modest amount of spin but only a small amount of heavy thunderstorms. Water vapor satellite images and the Saharan Air Layer analysis show that 97L is located in a dry environment, which is keeping development slow. Wind shear was a moderate 10 - 20 knots, which should allow some slow development. Sea Surface Temperatures are near 27.5°C, which is warm enough to allow some slow development. The wave should arrive in the Lesser Antilles Islands by Friday and be near Puerto Rico on Saturday, according to the Tuesday morning runs of the GFS model. None of the three reliable computer models for predicting tropical storm formation predict 97L will develop over the next five days. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave 97L 2-day and 5-day development odds of 0% and 20%, respectively. These odds are 10% lower than their previous advisory, and NHC has stopped running their suite of models on 97L.

New tropical wave coming off coast of Africa this weekend
A large and powerful tropical wave will move off the coast of Africa on Friday evening, and the GFS model has been very aggressive in recent runs about developing this wave into a tropical storm within a day of its emergence. The other reliable models for tropical cyclone genesis, the European and UKMET models, have not been developing this wave right away. Residents of the Cape Verde Islands should anticipate the possibility of heavy rain and strong winds on Saturday as the wave moves west at 10 - 15 mph across the islands. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave 97L 2-day and 5-day development odds of 0% and 30%, respectively.

The Gulf of Mexico is worth watching
In the Gulf of Mexico, heavy thunderstorm activity has diminished since Monday along a weak cold front stretching from South Florida to the Louisiana coastal waters. Some models show a weak area of low pressure developing along this front and moving westwards over Texas by Friday, and we should keep an eye on this region for development.


Figure 2. MODIS true-color image of Hurricane Marie in the Eastern Pacific taken at approximately 18:15 UTC (2:15 pm EDT) on August 25, 2014. At the time, Marie was a Category 4 storm with 145 mph winds. Image credit: NASA.

Powerful Hurricane Marie generating huge waves in Eastern Pacific
The Eastern Pacific's Hurricane Marie had weakened to a Category 2 storm with 105 mph winds on Tuesday morning, but was still generating huge swells that were bringing large waves to the coasts of Southern California and Mexico's Baja Peninsula. At 5 am EDT on Tuesday, Marie's tropical storm-force winds covered a huge area of ocean, up to 275 miles from the center, and 12-foot high seas extended up to 550 miles from the center. A High Surf Advisory is in effect for Los Angeles, where waves of 10 - 15 feet will potentially cause structural damage to piers and beachside property as well as significant beach erosion. The powerful surf will be accompanied by strong rip currents and long-shore currents, making for very hazardous swimming and surfing conditions through Thursday. Satellite loops on Tuesday morning showed a steady degradation of Marie's cloud pattern, with the eyewall cloud tops warming and the areal coverage of the strongest thunderstorms decreasing. The storm is headed to the northwest over cooler waters and into drier air, and will not affect any land areas.

You can see a spectacular loop of infrared satellite images of Marie as it intensified into a Category 5 storm on Sunday at the CIMSS University of Wisconsin.

Hurricane expert Steve Gregory, who subbed for me while I was on vacation last week, is now providing regular updates on the Atlantic in his blog, three times per week. Steve will sub for me again on Wednesday.

Jeff Masters