2012 NHC Product Changes

[brunota2003]

Haven't had a chance to read it yet, but here is the link:

http://www.nhc.noaa.gov/news/20120403_p ... hanges.pdf

[weatherwindow]

personally, i think the most exciting developments are the in-house experimental products noted on page 4...1) 7 day TC forecasts 2) 5 day TC formation forecasts 3) track and intensity forecasts for disturbances with a high likelihood of TC formation 4) issuance of TC warnings prior to formation where necessary....remember this are in house products not for public issue.....rich

[Chacor]

Taken from the NHC's submission to the forthcoming RA IV Hurricane Committee meeting, this is how TC warnings for a disturbance may look like (using pre-Tomas 2010), in a TWO:

ABNT20 KNHC 282342
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT THU OCT 28 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
WATCHES AND WARNINGS
--------------------
SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* BARBADOS...MARTINIQUE...DOMINICA…ST. LUCIA...ST. VINCENT AND THE GRENADINES...GRENADA...AND TRINIDAD AND TOBAGO

A HURRICANE WATCH IS IN EFFECT FOR...
* BARBADOS…MARTINIQUE…ST. LUCIA…AND ST. VINCENT AND THE GRENADINES

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN 24 HOURS.

A HURRICANE WATCH MEANS THAT HURRICANE CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE WITHIN 24 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

A VIGOROUS TROPICAL WAVE LOCATED OVER THE TROPICAL ATLANTIC ABOUT 725 MILES EAST-SOUTHEAST OF THE WINDWARD ISLANDS IS PRODUCING A LARGE AREA OF SHOWERS AND THUNDERSTORMS. THIS SYSTEM CONTINUES TO SHOW SIGNS OF ORGANIZATION...AND ENVIRONMENTAL CONDITIONS APPEAR TO BE FAVORABLE FOR GRADUAL DEVELOPMENT OF THIS DISTURBANCE DURING THE NEXT COUPLE OF DAYS AS THE SYSTEM IT MOVES WESTWARD OR WEST-NORTHWESTWARD AT 15 TO 20 MPH. THERE IS A HIGH CHANCE...60 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...THIS SYSTEM IS EXPECTED TO BRING LOCALLY HEAVY RAINFALL AND STRONG GUSTY WINDS TO THE WINDWARD ISLANDS... VENEZUELA...AND NORTHERN PORTIONS OF GUYANA DURING THE NEXT COUPLE OF DAYS. BECAUSE OF THE POTENTIAL FOR DEVELOPMENT AND THE PROXIMITY OF THE SYSTEM TO LAND…TROPICAL CYCLONE WATCHES AND WARNINGS ARE IN EFFECT FOR AREAS IDENTIFIED.

A SURFACE LOW PRESSURE AREA LOCATED ABOUT 450 MILES SOUTH-SOUTHEAST OF BERMUDA IS MOVING WEST-NORTHWEST AT 20 TO 25 MPH. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE LOW CONTINUE TO SHOW SOME SIGNS OF ORGANIZATION...AND THE CIRCULATION APPEARS TO BE GRADUALLY BECOMING BETTER DEFINED. ENVIRONMENTAL CONDITIONS ARE FORECAST TO REMAIN SOMEWHAT CONDUCIVE FOR THE DEVELOPMENT OF A TROPICAL OR SUBTROPICAL DEPRESSION THROUGH FRIDAY...HOWEVER UPPER-LEVEL WINDS
ARE EXPECTED TO BECOME LESS FAVORABLE AFTER THAT. THERE IS A HIGH CHANCE...70 PERCENT...OF THIS SYSTEM BECOMING A SUBTROPICAL OR TROPICAL CYCLONE BEFORE IT MERGES WITH A COLD FRONT ON SATURDAY.

A LOW PRESSURE SYSTEM IS LOCATED ABOUT 1200 MILES NORTHWEST OF THE NORTHERNMOST CAPE VERDE ISLANDS. ALTHOUGH SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH THE LOW HAS INCREASED DURING THE PAST FEW HOURS...UPPER-LEVEL WINDS ARE EXPECTED TO BECOME LESS FAVORABLE FOR DEVELOPMENT ON FRIDAY. THERE IS A MEDIUM CHANCE...30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY WESTWARD.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER READ

(This is an example published by the NHC in its submission here. It is not a real TWO.)

[CrazyC83]

A warning should only be issued when the probability of formation is 80% or higher though IMO (high-end code red, equivalent to categorical in forecasts). A watch should be issued at 30% or higher outside of 36 hours, or 30% to 70% within 36 hours (equivalent to chance or likely, code orange or low-end code red).

If the system has tropical storm force winds or higher but no closed circulation, that is an issue. In the CONUS, standard High Wind Warnings would normally apply there...but that is not a basin-wide standard.

[CrazyC83]

Some other thoughts:

If a storm becomes post-tropical or a remnant low, currently advisories shift to HPC as long as the system is a flood threat - but only if at least part of the circulation is over the CONUS, not the islands. I would recommend this change:

* The HPC should continue such advisories for ANY land area in the Atlantic basin that is experiencing, or expecting (within 36 hours), significant flooding or winds of at least 35 kt sustained. In the CONUS, the 35 kt winds would also allow for advisories to continue, regardless of flood situation.
* If the system is expected to regenerate within 48 hours, watches/warnings should be retained.
* All advisories should end if the system is not near land, or if weaker than 35 kt with no flood threat.