July Atlantic hurricane outlook
It's mid-July, and we have yet to see a named storm form in the Atlantic this month. The computer models are not predicting any development through at least July 20, and if we make it all the way to the end of the month without a named storm forming, it will be the first July since 2009 without a named storm. Since the current active hurricane period began in 1995, 13 of 17 years (76%) have had a named storm form during July. The busiest July occurred in 2005, when five named storms and two major hurricanes formed. These included Hurricane Dennis and Hurricane Emily--the strongest hurricanes ever observed so early in the season. Only eight major hurricanes have formed in July since record keeping began in 1851. As seen in Figure 1, most of the last half of July activity occurs in the Gulf of Mexico and waters off the Southeast U.S. coast. These type of storms form when a cold front moves off the U.S. coast and stalls out, with the old frontal boundary serving as a focal point for development of a tropical disturbance (as happened for Alberto, Beryl, Chris, and Debby in 2012.) There will be at least two cold fronts moving off the U.S. Mid-Atlantic coast over the next two weeks. The first of these fronts will push offshore around July 20, and we will need to watch the waters offshore of North Carolina for development then. Formation potential will be aided by ocean temperatures that are about 0.7°C (1°F) above average along the U.S. East Coast.
Figure 1. Tracks of all tropical storms and hurricanes 1851 - 2006 that formed July 16-31. The U.S. coast from North to Texas are the preferred strike locations. Only a few storms have formed in the tropical Atlantic and Caribbean in July. Wind shear is typically too high and SSTs too cool in July to allow African waves in the Caribbean and tropical Atlantic to develop into tropical storms. However, a few long-track "Cape Verdes" hurricanes have occurred in July, spawned by tropical waves that came off the coast of Africa. African tropical waves serve as the instigators of about 85% of all major hurricanes.
Figure 2. The seasonal distribution of Atlantic hurricane activity shows that July typically has low activity. Image credit: NHC.
Sea Surface Temperatures: slightly above average
The departure of Sea Surface Temperatures (SST) from average over the tropical Atlantic between Africa and Central America was about 0.3°C above average during June (Figure 3.) This figure has not changed much over the first two weeks of July. These temperatures are not warm enough to appreciably affect the odds of a July named storm or hurricane. The strength of the Azores-Bermuda high has been near average over the past two weeks, driving near-average trade winds. The latest 2-week run of the GFS model predicts continued average-strength trade winds through late-July, so SSTs should remain about 0.3°C above average during this period, due to average amounts of cold water mixing up from below due to the wind action on the water.
Figure 3. Sea Surface Temperature (SST) departure from average for July 12, 2012. SSTs were 0.3°C above average over the tropical Atlantic's Main Development region for hurricanes, from Africa to Central America between 10° and 20° North Latitude. Note the large region of above average SSTs along the Equatorial Pacific off the coast of South America, the hallmark of a developing El Niño episode. Image credit: NOAA/NESDIS
El Niño on the way?
For two consecutive weeks, ocean temperatures 0.5 - 0.6°C above average have been present in the tropical Eastern Pacific, which is right at the threshold for a weak El Niño episode. NOAA's Climate Prediction Center has issued an El Niño Watch, and gives a 61% chance that El Niño conditions will be present during the August - September - October peak of the Atlantic hurricane season. The likely development of a full-fledged El Niño episode means that Atlantic hurricane activity will probably be suppressed in 2012, due to the strong upper-level winds and high wind shear these events typically bring to the tropical Atlantic.
Figure 4. Sea Surface Temperature (SST) departure from average for the the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region"). El Niño conditions exist when the SST in this region rises 0.5°C above average. As of July 9, 2012, SSTs in the Niño 3.4 region had risen to 0.5°C above average. To be considered an "El Niño episode", El Niño conditions must occur for five consecutive months, using 3-month averages. Image credit: NOAA Climate Prediction Center.
Wind shear: above average
Wind shear is usually defined as the difference in wind between 200 mb (roughly 40,000 foot altitude) and 850 mb (roughly 5,000 foot altitude). In most circumstances, wind shear above 20 knots will act to inhibit tropical storm formation. Wind shear below 12 knots is very conducive for tropical storm formation. High wind shear acts to tear a storm apart. The jet stream has two bands of strong high-altitude winds that are currently bringing high wind shear to the Atlantic. The southern branch (subtropical jet stream) is bringing high wind shear to the Caribbean, and the northern branch (polar jet stream) is bringing high wind shear to the waters offshore of New England. This configuration often leaves a "hole" of low shear between the two branches, off the Southeast U.S. coast and over the Gulf of Mexico. The jet stream is forecast to maintain this two-branch pattern over the coming two weeks. Wind shear has been about 10 - 20% higher than average over the first two weeks of July, and is predicted to be mostly above average for the coming two weeks. This will cut down on the odds of a July storm.
Figure 5. Vertical instability over the Caribbean Sea in 2012 (blue line) compared to average (black line.) The instability is plotted in °C, as a difference in temperature from near the surface to the upper atmosphere. Thunderstorms grow much more readily when vertical instability is high. Instability has been lower than average, due to an unusual amount of dry air in the atmosphere, reducing the potential for tropical storm formation. Image credit: NOAA/NESDIS/CIRA.
Dry air: above average
As seen in Figure 5, there has been an unusual amount of dry, stable air in the Caribbean this year creating low levels of vertical instability. This has occurred due to a combination of dry air from Africa, and upper-atmosphere dynamics creating large areas of sinking air that dry as they warm and approach the surface. The Gulf of Mexico and tropical Atlantic between the coast of Africa and the Lesser Antilles have also seen low vertical instability this summer. June and July are the peak months for dry air and dust coming off the coast of Africa, and the Saharan dust storms have been quite active over the past two weeks. Expect dry air to be a major deterrent to any storms that try to form in the tropical Atlantic during July.
Steering currents: average
The predicted steering current pattern for the next two weeks is a typical one for July. We have an active jet stream bringing many troughs of low pressure off the East Coast of the U.S. These troughs are frequent enough and strong enough to recurve any tropical storms or hurricanes that might penetrate north of the Caribbean Sea. Steering current patterns are predictable only about 3 - 5 days in the future, although we can make very general forecasts about the pattern as much as two weeks in advance. There is no telling what might happen during the peak months of August, September, and October--we might be in for a repeat of the favorable 2010 and 2011 steering current pattern, which recurved most storms out to sea--or the unfavorable 2008 pattern, which steered Ike and Gustav into the Gulf of Mexico.
Summary: a below average chance of a July tropical storm
Given that none of the computer models are forecasting tropical storm formation in the coming seven days, SSTs are only slightly above average, and wind shear and vertical stability are above average, I'll go with a 30% chance of a named storm forming in the Atlantic during the remainder of July.
Figure 6. Hurricane Emilia over the Eastern Pacific at 20:35 UTC July 10, 2012. At the time, Emilia was a Category 3 hurricane with 125 mph winds. Emilia peaked earlier in the day as a Category 4 storm with 140 mph winds--the strongest hurricane in the East Pacific so far in 2012. Image credit: NASA.
An active Eastern Pacific hurricane season
It's been a very active start to the Eastern Pacific hurricane season, where we've already had six named storms, four hurricanes, and three intense hurricanes. A typical season has 4 named storms, 2 hurricanes, and 0 intense hurricanes by July 14. The formation of Tropical Storm Fabio on July 12 marks the 4th earliest formation of the Eastern Pacific's season's sixth storm. The record is held by the year 1985, when the season's sixth storm formed on July 2. Record keeping began in 1949.
Have a great weekend, everyone, and I'll be back Monday with a new post.
Jeff Masters
Reader Comments
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CYPRESS CREEK NEAR WESTFIELD AFFECTING HARRIS AND MONTGOMERY COUNTIES
AFFECTING THE FOLLOWING COUNTIES IN TEXAS...HARRIS...MONTGOMERY
FOR THE CYPRESS CREEK, AT WESTFIELD, MINOR FLOODING IS OCCURING AND IS EXPECTED
TO CONTINUE.
HEAVY RAINS FROM THE PAST FEW DAYS HAS CAUSED SIGNIFICANT RISES ALONG THE RIVER.
A SECONDARY RISE IS EXPCETED TODAY CAUSING THE RIVER TO RISE ABOVE FLOOD STAGE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
PERSONS ARE URGED TO STAY AWAY FROM THE RIVER UNTIL WATER LEVELS RECEDE.
MOTORISTS SHOULD AVOID ANY WATER COVERED ROADS AND FIND AN ALTERNATE ROUTE.
LIVESTOCK AND EQUIPMENT SHOULD REMAIN OUT OF THE FLOOD PLAIN FOR THE NEXT FEW
DAYS.
STAY TUNED TO NOAA WEATHER RADIO OR OTHER NEWS SOURCES FOR FURTHER UPDATES.
I stay here for awhile and keep posting from the great lakes state.
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm
----- Current Analysis -----
Date : 14 JUL 2012 Time : 143000 UTC
Lat : 16:14:08 N Lon : 114:10:50 W
CI# /Pressure/ Vmax
4.4 / 980.8mb/ 74.6kt
Final T# Adj T# Raw T#
4.2 3.7 3.6
Center Temp : -52.4C Cloud Region Temp : -68.8C
Scene Type : UNIFORM CDO CLOUD REGION
Positioning Method : SPIRAL ANALYSIS
Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : PACIFIC
Tno/CI Rules : Constraint Limits : 0.7T/6hr
Weakening Flag : ON
Rapid Dissipation Flag : OFF
KEEP an eye on that..maybe hourly updates! LOL ROFL
Hurricane Andrew was the first "A" storm in an El Nino year that did not form until the end of August. I believe there were only 9 named storms that year but the steering for that particular storm was the main factor and the relaxation of sheer as it crossed the Gulf Stream area which caused a sudden intensification event. I was living with my Girlfriend at what turned out to be ground zero the next Monday morning near Metro Zoo and we made a last minute decision to stay at out respective parent's houses further North for the storm. The house was gone the next morning. Those are the facts:
El Niño, which began in June, is expected to last through winter and into 2010. While its wind shear seems to have suppressed Atlantic hurricane activity for two months, Bell warns not even El Niño can stop every hurricane.
"We're in the peak of the hurricane season, so people need to be ready for hurricane season," he says. "It only takes one. You can have a low-activity era like in 1992 — that's when we had Hurricane Andrew devastate South Florida."
Is this the wave or something behind it?
I know my emotional condition is based on this blog!
Hurricane Iwa Category 1 hurricane (SSHS)
Hurricane Iwa satellite image.
Formed November 19, 1982
Dissipated November 25, 1982
Highest winds 1-minute sustained:
90 mph (150 km/h)
Lowest pressure 968 mbar (hPa); 28.59 inHg
Fatalities 1 direct, 3 indirect
Damage $312 million (1982 USD)
Areas affected Hawaiʻi
Part of the 1982 Pacific hurricane season
Hurricane Iwa, taken from the Hawaiian language name for the frigatebird (ʻiwa, lit. "Thief"), was at the time the costliest hurricane to affect the state of Hawaiʻi. Iwa was the twenty-third tropical storm and the twelfth and final hurricane of the 1982 Pacific hurricane season. It developed from an active trough of low pressure near the equator on November 19. The storm moved erratically northward until becoming a hurricane on November 23 when it began accelerating to the northeast in response to strong upper-level flow from the north. Iwa passed within 25 miles of the island of Kauaʻi with peak winds of 90 mph (145 km/h) on November 23 (November 24 Coordinated Universal Time), and the next day it became extratropical to the northeast of the state.
The hurricane devastated the islands of Niʻihau, Kauaʻi, and Oʻahu with wind gusts exceeding 100 mph (160 km/h) and rough seas exceeding 30 feet (9 m) in height. The first significant hurricane to hit the Hawaiian Islands since statehood in 1959, Iwa severely damaged or destroyed 2,345 buildings, including 1,927 houses, leaving 500 people homeless. Damage throughout the state totaled $312 million (1982 USD, $751 million 2012 USD). One person was killed from the high seas, and three deaths were indirectly related to the hurricane's aftermath.
The Carrington Event of 1859 was the first documented event of a solar flare impacting Earth. The event occurred at 11:18 a.m. EDT on Sept. 1 and is named after Richard Carrington, the solar astronomer who witnessed the event through his private observatory telescope and sketched the sun's sunspots at the time. The flare was the largest documented solar storm in the last 500 years, NASA scientists have said.
According to NOAA, the Carrington solar storm event sparked major aurora displays that were visible as far south as the Caribbean. It also caused severe interruptions in global telegraph communications, even shocking some telegraph operators and sparking fires when discharges from the lines ignited telegraph paper, according to a NASA description.
Good morning Largo
A CV storm would be nice so some people would stop saying the season is a bust, if anyone is saying that.
wxchaser people are all ready calling this season a bust.
FXUS66 KSGX 141116
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
415 AM PDT SAT JUL 14 2012
.SYNOPSIS...
A WEAK TROUGH OF LOW PRESSURE ALONG THE WEST COAST WILL BRING
GRADUAL DRYING THROUGH EARLY NEXT WEEK WITH DECREASING CHANCES OF
SHOWERS AND THUNDERSTORMS IN THE MOUNTAINS AND DESERTS. THERE IS A
SMALL CHANCE THAT MID AND HIGH LEVEL MOISTURE FROM THE REMNANTS OF
HURRICANE FABIO COULD BE DRAWN NORTHWARD ACROSS THE AREA WEDNESDAY
NIGHT AND THURSDAY FOR A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS.
MONSOONAL MOISTURE IN SOUTHEAST FLOW ALOFT COULD RETURN SOME TIME
NEXT WEEKEND FOR A RENEWED CHANCE OF SHOWERS AND THUNDERSTORMS.
ONSHORE FLOW AND THE MARINE LAYER WILL BRING AREAS OF NIGHT AND
MORNING LOW CLOUDS AND FOG FOR COASTAL AREAS EXTENDING LOCALLY
INLAND.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY THROUGH MONDAY)...
A WEAK UPPER TROUGH OF LOW PRESSURE WILL REMAIN ALONG THE WEST COAST
THROUGH MONDAY. WITHIN THIS LARGER TROUGH OF LOW PRESSURE...ONE WEAK
SHORTWAVE WAS MOVING NORTHWARD THROUGH WESTERN ARIZONA WITH ANOTHER
MOVING SOUTHWARD ALONG THE CENTRAL CALIFORNIA COAST. RADAR SHOWS A
FEW RESIDUAL LIGHT SHOWERS OVER THE LOWER DESERT AREAS. THE
SHORTWAVE ALONG THE CENTRAL CALIFORNIA COAST WILL BRING ADDITIONAL
DRYING TO SOUTHERN CALIFORNIA TODAY. THE DRIER GFS AND ECMWF
PRECIPITATION FORECASTS MESH BETTER WITH CURRENT RADAR AND EXPECTED
TRENDS VERSUS THE WETTER NAM. THE CURRENT FORECAST RETAINS A SLIGHT
CHANCE OF PRECIPITATION ON THE DESERT SLOPES OF THE MOUNTAINS AND
ADJACENT DESERT AREAS FOR THIS AFTERNOON AND EARLY EVENING FOR ANY
THUNDERSTORMS RESULTING FROM RESIDUAL MOISTURE EAST OF THE
MOUNTAINS. ADDITIONAL DRYING SHOULD END ANY THUNDERSTORM CHANCES FOR
THE NEXT FEW DAYS AFTER THIS EVENING.
SATELLITE IMAGERY ALSO SHOWS MORE EXTENSIVE STRATUS OVER THE COASTAL
WATERS EXTENDING LOCALLY INLAND TO THE FAR WESTERN VALLEYS. AS
DRYING ALOFT OCCURS AND WEAK ONSHORE FLOW RETURNS...THERE SHOULD BE
GREATER COVERAGE THE NEXT FEW NIGHTS WITH SLOW DEEPENING OF THE
MARINE LAYER ALLOWING THE STRATUS TO EXTEND A LITTLE FARTHER INLAND
INTO THE VALLEYS EACH NIGHT.
&&
.LONG TERM (TUESDAY THROUGH FRIDAY)...
A WEAK UPPER TROUGH OF LOW PRESSURE WILL REMAIN NEAR THE WEST COAST
THROUGH MID WEEK...THEN GRADUALLY WEAK INTO NEXT WEEKEND AS HIGH
PRESSURE TO THE EAST EXPANDS SLOWLY TOWARDS THE WEST NEXT WEEKEND.
IN THE SOUTH FLOW ALOFT BETWEEN THE TROUGH OF LOW PRESSURE TO THE
NORTHWEST AND THE HIGH PRESSURE TO THE EAST...SOME MID AND HIGH
LEVEL MOISTURE FROM THE REMNANTS OF HURRICANE FABIO COULD BE DRAWN
NORTHWARD ACROSS PORTIONS OF SOUTHERN CALIFORNIA WEDNESDAY NIGHT AND
THURSDAY. THE CURRENT FORECAST SHOWS SOME INCREASE IN CLOUD COVER
AND POPS SLIGHTLY ABOVE CLIMATOLOGY...BUT NOT QUITE HIGH ENOUGH FOR
PRECIPITATING WEATHER. SOME TIME NEXT WEEKEND...HIGH PRESSURE THE
EAST COULD BEGIN TO DIRECT SOME MONSOONAL MOISTURE INTO SOUTHERN
CALIFORNIA BRINGING A RENEWED CHANCE OF SHOWERS AND THUNDERSTORMS.
Why would it be bad? Boring yes, but for those of us that live near the coast, boring is good. ;)
During the next cat4 why don't you come down, buy some property and stay awhile. I think you'd then like boring. Lol
Conditions are not that favorable in the Atlantic right now. The is a large ULL in the Central Atlantic. The current wave you see, should help moisten the atmosphere though.
The shear forecast is also high, also a lot of dry air ahead of the current wave.
In a few days, conditions will be more favorable for development, but nothing immediate. The MJO will be favorable at the end of July.
http://www.swpc.noaa.gov/rt_plots/mag_3d.html
Yes,that ULL needs to go away to turns things more favorable. Thank you for the brief take on it.
You're welcome.
That is the one I was mentioning that could have a chance.
Effective May 17, 2011
Effective Tuesday, May 17, 2011, beginning with the 1200
Coordinated Universal Time (UTC) run, the National Centers
for Environmental Prediction (NCEP) will upgrade the
Geophysical Fluid Dynamics Laboratory (GFDL) Hurricane
Prediction System. The scientific changes to the model
include the following:
- Upgrade Simplified Arakawa-Schubert (SAS) deep convection
parameterization to new version implemented in the NCEP
Global Forecast System (GFS)
- Modify the surface enthalpy exchange coefficient and
dissipative heating effect
- Expand coupled region in the Eastern Atlantic domain
to prevent storms from losing coupling effect with the
ocean due to insufficient overlap with the Western Atlantic
region. The new overlap will be 25 degrees.
- Correct several bugs in the model.
In testing, these improvements resulted in an average reduction
of forecast error of about 20 percent in the Atlantic basin
for the 3 to 5 day forecast period for tests of storms from
the 2010 Atlantic hurricane season.
Now let's see if the models start to pick it up in the next few runs.
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