Vance Forms in the Eastern Pacific; the Atlantic Goes Quiet

By: Dr. Jeff Masters , 3:05PM,GMT on October 31,2014

Tropical Storm Vance formed in the Eastern Pacific on Thursday afternoon. Satellite images show that Vance is struggling with dry air and wind shear, with just a modest area of heavy thunderstorms that had not improved in organization since Thursday. By Saturday, the wind shear should relent, allowing intensification into a Category 1 hurricane by Sunday. The storm's heaviest rains will remain well offshore from Mexico through Sunday, but our two top models for predicting hurricane tracks--the GFS and European models--forecast that Vance will get pulled to the northeast by a trough of low pressure early next week, and make landfall in Mainland Mexico northwest of Puerto Vallarta on Tuesday night. The 8 am EDT Friday run of the SHIPS model predicted that wind shear would remain low, 5 - 10 knots, though Monday, then ramp up significantly on Monday night and Tuesday as Vance gets caught up in the trough of low pressure that will sling it into Mexico. The higher wind shear should be able to significantly weaken Vance before landfall, making heavy rain the primary threat. In their 11 am EDT Friday Wind Probability Forecast, NHC gave a 15% chance that Vance would bring tropical storm-force winds of 39+ mph to Puerto Vallarta and the tip of the Baja Peninsula. Vance's moisture will likely bring heavy rain and the threat of flooding to Texas on Wednesday.


Figure 1. VIIRS satellite image of Tropical Storm Vance off the Pacific coast of Mexico on Thursday, October 30, 2014. At the time, Vance had top sustained winds of 40 mph. Image credit: NOAA Visualization Lab.

A near-record active 2014 Eastern Pacific hurricane season
Vance's formation gives the 2014 Eastern Pacific (east of 140°W) 20 named storms, 13 hurricanes, and 8 intense hurricanes in 2014. An average Eastern Pacific hurricane season sees 15 named storms, 8 hurricanes, and 3 intense hurricanes during the entire year. This year is the busiest year since 1992, which set records for total number of named storms (25), hurricanes (14), and intense hurricanes (8). If we include the Central Pacific between 140°W and 180°W, these record tallies in 1992 were 28 named storms, 16 hurricanes, and 10 intense hurricanes. The 2014 totals in the combined Eastern and Central Pacific basins so far are 21 named storms, 15 hurricanes, and 9 intense hurricanes (Genevieve did not become a hurricane and then major hurricane until it crossed from the Eastern Pacific into the Central Pacific, and Category 1 Hurricane Ana existed only in the Central Pacific, not the Eastern Pacific.) On average, we can expect one more named storm and no hurricanes in the Eastern Pacific in November; I expect we will get 1 - 2 more named storms--Winnie and Xavier--this year, after Vance.

Arabian Sea's Tropical Cyclone Nilofar destroyed by wind shear
In the Arabian Sea between India and Africa, Cyclone Nilofar has been shredded by high wind shear of 50 knots, and the Joint Typhoon Warning Center has issued its last advisory on the system. Nilofar's remnants will bring a few areas of heavy rain to the India/Pakistan border region.


Figure 2. MODIS satellite image of Tropical Cyclone Nilofar in the Arabian Sea on Friday morning, October 31, 2014. At the time, Nilofar was a dissipating tropical storm with 40 mph winds, and the low-level circulation had been exposed to view by high wind shear. Image credit: NASA.

Tropical Storm Nuri forms in Western Pacific
The Western Pacific has become active again, with the formation of Tropical Storm Nuri. Nuri is headed towards Japan, and may pass close enough to Japan next Thursday and Friday to bring them heavy rain.

Quiet in the Atlantic
The Atlantic is quiet today, with no areas of concern to discuss. None of the three reliable models for predicting tropical cyclone genesis predicts any development in the Atlantic over the next five days. With November at hand and El Niño-like atmospheric conditions in place, the odds of getting Tropical Storm Isaias before the end of the Atlantic hurricane season on November 30 are probably around 30%.

Jeff Masters